Characterization of the murine antigenic determinant, designated L3T4a, recognized by monoclonal antibody GK1.5: expression of L3T4a by functional T cell clones appears to correlate primarily with class II MHC antigen-reactivity

Th2-Induced Airway Mucus Production Is Dependent on IL-4Rα, But Not on Eosinophils

Mucus hyperproduction in asthma results from airway inflammation and contributes to clinical symptoms, airway obstruction, and mortality. In human asthmatics and in animal models, excess mucus production correlates with airway eosinophilia. We previously described a system in which TCR transgenic CD4 Th2 cells generated in vitro were transferred into recipient mice and activated in the respiratory tract with inhaled Ag. Th2 cells stimulated airway eosinophilia and a marked increase in mucus production, while mice that received Th1 cells exhibited airway inflammation without eosinophilia or mucus. Mucus could be induced by IL-4−/− Th2 cells at comparable levels to mucus induced by IL-4+/+ Th2 cells. In the current studies we dissect further the mechanisms of Th2-induced mucus production. When IL-4−/− Th2 cells are transferred into IL-4Rα−/− mice, mucus is not induced, and BAL eosinophilia is absent. These data suggest that in the absence of IL-4, IL-13 may be critical for Th2-induced mucus production and eosinophilia. To determine whether eosinophils are important in mucus production, IL-5−/− Th2 cells were transferred into IL-5−/− recipients. Eosinophilia was abolished, yet mucus staining in the epithelium persisted. These studies show definitively that IL-5, eosinophils, or mast cells are not essential, but signaling through IL-4Rα is critically important in Th2 cell stimulation of mucus production.

T-cell activation, proliferation, and memory after cardiac transplantation in vivo

OBJECTIVE

To study the response of alloantigen (H2Kb)-specific T cells to a H2b+ cardiac allograft in vivo.

SUMMARY BACKGROUND DATA

The response of T cells to alloantigen has been well characterized in vitro but has proved more difficult to assess in vivo. The aim of these experiments was to develop a model of T-cell-mediated rejection where the response of T cells after transplantation of a cardiac allograft could be followed in vivo.

METHODS

Purified CD8+ T cells from H2Kb-specific TCR transgenic mice (BM3; H2k) were adoptively transferred into thymectomized, T-cell-depleted CBA/Ca (H2k) mice. These mice were then transplanted with a H2Kb+ cardiac allograft. Using four-color flow cytometry, the proliferative response, modulation of activation markers, and potential cytokine production of the H2Kb-specific T cells was assessed after transplantation.

RESULTS

Consistent rejection of H2Kb+ cardiac allografts required the transfer of at least 6 x 10(6) CD8+ H2Kb-specific T cells. Short-term analyses revealed that the transgenic-TCR+/ CD8+ T cells proliferated and became activated after transplantation of an H2Kb+ cardiac allograft. Fifty days after transplantation, the transgenic-TCR+/CD8+ T cells remained readily detectable, bore a predominantly memory phenotype (CD44hi), and rapidly produced interleukin 2 and interferon-gamma on in vitro restimulation.

CONCLUSIONS

These data show that the activation of alloantigen-specific T cells can be followed in vivo in short-term and long-term experiments, thereby providing a unique opportunity to study the mechanisms by which T cells respond to allografts in vivo.

Temporal sequence of transcription of perforin, Fas ligand, and tumor necrosis factor-alpha genes in rejecting skin allografts

BACKGROUND

Perforin, Fas ligand (FasL), and tumor necrosis factor-alpha (TNF-alpha) have been implicated in cytolytic T lymphocyte (CTL) effector function. However, the relative roles of these effector molecules in allograft rejection are unclear, and there has been no rigorous quantitation of transcription of the respective genes throughout the period from transplantation to rejection.

METHODS

We orthotopically transplanted mouse tail skin allografts and estimated the numbers of transcripts of these genes expressed by graft-infiltrating T cells with rigorous quantitative, competitive reverse transcribed PCR (QC-RT-PCR) that enabled the comparison of transcription of different genes.

RESULTS

Perforin and FasL mRNA levels correlated closely with the rejection of allografts by normal hosts over the 4 days preceding rejection. Antibody-mediated depletion of host CD4+ T cells retarded perforin transcription and significantly suppressed FasL transcription, suggesting FasL was not required for allograft rejection. TNF-alpha transcription was the highest of these genes in this time period, but these levels were dwarfed by TNF-alpha transcription at 24 hr posttransplant when transcription in both autografts and allografts was 30-fold higher than in allografts on the day before rejection. Elimination of the function of these single or paired genes through genetic mutation or antibody treatment had no significant effect on the speed of rejection.

CONCLUSIONS

The levels of perforin and FasL transcription appeared to be related to the process of allograft rejection in normal hosts. However, TNF-alpha transcription was highest during the posttransplant period suggesting that the principal role of TNF-alpha is in wound-healing rather than the effector phase of rejection.

IFN-γ and CD8+ T Cells Restore Host Defenses Against Pneumocystis carinii in Mice Depleted of CD4+ T Cells

Host defenses against infection are profoundly compromised in HIV-infected hosts due to progressive depletion of CD4+ T lymphocytes and defective cell-mediated immunity. Although recent advances in antiretroviral therapy can dramatically lower HIV viral load, blood CD4+ T lymphocytes are not restored to normal levels. Therefore, we investigated mechanisms of host defense other than those involving CD4+ T lymphocytes against a common HIV-related opportunistic infection, Pneumocystis carinii (PC) pneumonia. Using CD4-depleted mice, which are permissive for chronic PC infection, we show that up-regulation of murine IFN-γ by gene transfer into the lung tissue results in clearance of PC from the lungs in the absence of CD4+ lymphocytes. This resolution of infection was associated with a >4-fold increase in recruited CD8+ T lymphocytes and NK cells into the lungs. The role of CD8+ T cells as effector cells in this model was further confirmed by a lack of an effect of IFN-γ gene transfer in scid mice or mice depleted of both CD4+ and CD8+ T cells. Cytokine mRNA analysis revealed that recruited, lung-derived CD8+ T cells had greater expression of IFN-γ message in animals treated with the IFN-γ gene. These results indicate that CD8+ T cells are capable of clearing PC pneumonia in the absence of CD4+ T cells and that this host defense function of CD8+ T cells, as well as their cytokine repertoire, can be up-regulated through cytokine gene transfer.

Herpes simplex virus as an in situ cancer vaccine for the induction of specific anti-tumor immunity

The success of cancer gene therapy is likely to require the targeting of multiple antitumor mechanisms. One strategy involves the use of attenuated, replication-competent virus vectors, such as herpes simplex virus type 1 (HSV-1) mutant G207, which is able to replicate in human tumor cells with resultant cell death and tumor growth inhibition, yet is nonpathogenic in normal tissue. In this study, we demonstrate that infection of established tumors with G207 also induces a highly specific systemic anti-tumor immune response. In a syngeneic, bilateral established subcutaneous tumor model, with mouse CT26 colorectal carcinoma cells in BALB/c mice or M3 melanoma cells in DBA/2 mice, unilateral intratumoral inoculation with G207 caused a significant reduction in the growth of both the inoculated and contralateral noninoculated tumors. This elicited anti-tumor response is dependent on viral infection of the tumor, as intradermal inoculation of G207 in BALB/c mice had no effect on CT26 tumor growth. Treatment of subcutaneous CT26 tumors by intratumoral inoculation of G207 induced a tumor-specific T cell response. CD8+ cytotoxic T lymphocyte (CTL) activity was generated that recognized a dominant "tumor-specific" major histocompatibility complex (MHC) class I-restricted epitope (AH1) from CT26 cells. In immune-competent animals, G207 is acting as an in situ tumor vaccine. Therefore, intratumoral G207 inoculation is able to inhibit tumor growth both by local cytotoxic viral replication in tumor cells and induction of a systemic anti-tumor immune response.

Profound Enhancement of T Cell Activation Mediated by the Interaction Between the TCR and the D3 Domain of CD4

CD4 plays an important role in the activation and development of CD4+ T cells. This is mediated via its bivalent interaction with MHC class II molecules and the TCR:CD3 complex through p56lck. Recent studies have implicated a third site of interaction between the membrane-proximal extracellular domains of CD4 and the TCR. Due to these multiple interactions, direct evidence for the functional importance of this extracellular association has remained elusive. Furthermore, the residues that mediate this interaction are unknown. In this study, we analyzed the function of 61 CD4 mutants. Alanine substitution of just 2 residues, either Q114/F182 or F182/F201, which are partially buried and located close to the D2/D3 interface, completely abrogated CD4 function. Direct evidence for the functional importance of TCR:CD4.D3 interaction was obtained using an anti-CD3fos:anti-CD4jun-bispecific Ab. Surprisingly, it induced strong T cell activation in hybridomas transfected with cytoplasmic-tailless CD4, despite the lack of association with either p56lck or MHC class II molecules. However, this effect was completely abrogated with the CD4 mutants Q114A/F182A or F182A/F201A. These data demonstrate that TCR:CD4.D3 interaction can have a profound effect on T cell activation and obviates the need for receptor oligomerization.

Chicken CD4, CD8alphabeta, and CD8alphaalpha T cell co-receptor molecules

New knowledge has recently been obtained about the evolutionary conservation of CD4, CD8alphaalpha, and CD8alphabeta T cell receptor (TCR) co-receptor molecules between chicken and mammals. This conservation extends from biochemical structure and tissue distribution to function. Panels of monoclonal antibodies and polyclonal antisera against different epitopes of chicken CD8 and CD4 molecules have proven their value in several recent studies. Chicken CD8 allotypes and homozygous strains carrying these allotypes have been established and these strains provide excellent models for further studies. The extensive polymorphism of CD8alpha in chickens has not been observed in any other species, suggesting that CD8alpha and CD8beta have evolved under different selective pressure in the chicken. A large peripheral blood CD4+CD8+ T cell population in chicken resembles that observed in some human individuals but the inheritance of peripheral blood CD4CD8alphaalpha T cells in the chicken is a unique observation, which suggests the presence of a single gene responsible for CD8alpha, but not CD8beta, specific expression. Despite these unique findings in chicken, the data on CD4, CD8alphaalpha, and CD8alphabeta molecules show that they have evolved before the divergence of mammalian and avian branches from their reptilian ancestors.

CD8(+), radiosensitive T cells of parental origin, oppose cells capable of down-regulating cytotoxicity in murine acute lethal graft-versus-host disease

Murine graft-versus-host (GVH) disease takes two forms depending upon the parental/F1 strain combination employed. Anemia, lymphopenia, hypogammaglobulinemia, profound anti-F1 cytotoxicity, and the loss of cytotoxic potential against third party alloantigen is seen in acute lethal GVH disease. In contrast to this, in chronic GVH disease there is polyclonal B cell activation, auto-antibody production, no anti-F1 cytotoxicity, and retained cytotoxicity against allotargets. We have previously reported that this marked disparity in disease expression results from a radiosensitive host veto cell which protects the F1 mouse from parental anti-F1 cytotoxicity in mice undergoing CGVH disease. This cell could be induced in vitro or in vivo in CGVH disease. Using an in vitro system, we now demonstrate that a CD4(+), radiation-sensitive, T cell does emerge in acute lethal GVH disease which is capable of down-regulating cytotoxicity. The cell does not appear to be a veto cell in that it attenuates cytotoxicity directed against nonself alloantigen. The function of this cell does not appear to be influenced by minor lymphocyte stimulatory gene products. We further report that, in ALGVH disease, regulation by this cell is not readily apparent due to the emergence of a CD8(+) T cell of parental (B6) origin, which opposes its action.

Self-Restricted Dual Receptor Memory T Cells

Enhanced immune responses during secondary exposure to Ag result from the development of memory cells. In the present report we show that stimulation through one receptor on dual receptor CD4 cells can promote the generation of T cells capable of giving a memory response through the second receptor, even though the cells had not been previously exposed to the Ag recognized by the second receptor. Cloned cells generated from dual receptor memory T cells proliferated and secreted the same lymphokines after stimulation with either Ag. Independent recognition of both Ags by distinct TCRs was shown by production of variants that had lost either Ag specificity along with the corresponding TCR. Recognition of both Ags is MHC restricted, since the cells recognize Ag presented by self, but not non-self, MHC class II molecules. These results raise the possibility that one potential mechanism of maintaining specific memory to a given Ag is through stimulation by an unrelated Ag via the second TCR.

Macrophages may activate or destroy T cells with which they form antigen- or coreceptor-mediated cellular conjugates

The formation of antigen- or mitogen-mediated cellular conjugates with T cells enables macrophages to trigger in T cells costimulatory signals and to facilitate T cell clonal expansion and differentiation. The present study describes T cell death as an alternative consequence of T cell interaction with macrophages. Macrophages initiate the deletion of T cells which they target for conjugate formation through CD4 coreceptors. After suboptimal engagement, the TCR mediates a deletion program. Optimal TCR stimulation induces a rescue program which overrides the deletion program induced by suboptimal antigen receptor ligation or by coreceptor engagement. Evidence is presented suggesting that receptor clustering favors the transmission of activation signals, whereas ligation of nonclustered receptors facilitates T cell deletion.

Urocanic Acid Enhances IL-10 Production in Activated CD4+ T Cells

The immunosuppressive effects of UV radiation have been well documented. This suppression has been attributed to the action of the cis form of urocanic acid (UCA), a photoproduct of trans-UCA, a natural constituent of the skin. Here, we show that mouse spleen cells preincubated with cis-UCA have a diminished proliferative response to allogeneic cells in MLC and to stimulation with anti-CD3 mAb. Cells preincubated with cis-UCA also had a decreased ability to serve as APC and to stimulate the proliferation of allogeneic lymphocytes in MLC. Simultaneously, the production of IL-2 and IFN-γ by cells preincubated with cis-UCA was decreased. However, IL-10 gene expression and IL-10 protein secretion by spleen cells stimulated in the presence of cis-UCA were significantly enhanced. The principal cell population displaying the cis-UCA-induced elevated production of IL-10 was CD4+ T cells, which were shown to be a direct target of cis-UCA action. This was also supported by the observation that production of IL-10 by stimulated splenic non-T cells or by macrophages was not altered by cis-UCA. The enhanced production of IL-10 by activated CD4+ T cells may represent a novel pathway of UVB radiation-induced, cis-UCA-mediated immunosuppression. We suggest that the elevated production of IL-10 by activated CD4+ T cells may account for the suppressor T cell phenomena described in UV-irradiated recipients.

Autoimmunity Without Diabetes in Transgenic Mice Expressing β Cell-Specific CD86, But Not CD80: Parameters that Trigger Progression to Diabetes

To define more clearly the roles of CD80 (RIP-CD80) and CD86 (RIP-CD86) in the activation of autoreactive T cells in vivo, we generated transgenic mice expressing either or both costimulatory molecules on the β cells of the pancreas. While RIP-CD80 mice do not show any sign of autoimmunity, at the age of 7 mo RIP-CD86 transgenic mice develop a lymphoid infiltrate with both IFN-γ- and IL-4-positive cells in the vicinity of the islets; these mice, however, never progress to diabetes. This fundamental difference in the ability of CD80 and CD86 to activate self-reactive T cells in vivo is, however, obliterated when the level of TCR signaling is increased by either TNF-α or transgenic MHC class II expression. These results support the suggestion that CD80 and CD86 mainly differ at the level of the intensity of the signals they deliver.

Visualizing memory phenotype development after in vitro stimulation of CD4(+) T cells

Stimulation of naive CD4 cells by specific antigen results in proliferation and changes in cell surface marker expression as the cells differentiate into effector and memory cells. Several of the marker changes (e.g., differences in CD45RB, CD44, and L-selectin levels) appear to be relatively stable and permit the identification of memory T cells. In this study, we examined the acquisition of memory markers after the initial stimulation of naive T cells. CD4(+) T cells from DO11.10 TCR transgenic mice were labeled with the fluorescent dye carboxyfluorescein diacetate succinimidyl ester (CFSE) and were stimulated with specific antigen (OVA323-339). Specific activation was observed, as CFSE-associated fluorescence was reduced twofold with each division of DO11.10 clonotype-bearing cells. Phenotypic changes could also be observed as the cells differentiated into effector/memory cells. However, individual surface markers exhibited a varied relationship to cell division. Although changes in some markers (L-selectin) occurred independently of cell division, changes in other markers were either strictly related to cell division (CD45RB) or were a prerequisite to cell division (CD4, CD44).

Induction of Acute Inflammation In Vivo by Staphylococcal Superantigens. II. Critical Role for Chemokines, ICAM-1, and TNF-α

Superantigens such as staphylococcal enterotoxin A and B (SEA and SEB) activate the immune system by stimulating a large proportion of T lymphocytes through specific Vβ regions of the TCR and activating macrophages by binding to MHC class II molecules. While the mechanisms by which superantigens activate T lymphocytes have been elucidated, their role in the generation of local immune responses to bacterial invasion is still unclear. In this study we have examined the ability of the superantigens SEA and SEB to elicit an inflammatory reaction in vivo, in s.c. air pouches in the mouse. Upon injection into the s.c. air pouch, the two superantigens stimulated a time-dependent increase in the number of leukocytes appearing in the pouch exudate. The leukocytes migrating into the pouch exudate were predominantly neutrophils, with some mononuclear phagocytes and eosinophils present. No T lymphocytes were detected either in the pouch lining tissue or in the exudate cells. Injection of SEA resulted in increased ICAM-1 expression, as detected by immunohistochemistry, on endothelial cells in the tissue surrounding the air pouch and accumulation of TNF-α and the chemokines macrophage inflammatory protein-2 (MIP-2), MIP-1α, and JE in the pouch exudate. In addition, pretreatment of mice with Abs raised against ICAM-1, TNF-α, MIP-2, MIP-1α, KC, or JE inhibited leukocyte accumulation induced by SEA. These data demonstrate that bacterial superantigens may promote inflammation at extravascular sites in vivo, and that this response is secondary to the generation of inflammatory mediators, including chemokines.

Role of Maternal Ig in the Induction of Cκ-Specific CD8+ T Cell Tolerance

Although the influence of maternal Ig on the B cell repertoire and subsequent Ab response has been extensively studied, much less attention has been devoted to their effects on T cell responses of the offspring. To address this question, we have studied the influence of maternal κ-positive Ig (Igκ) on the Cκ-specific CD8+ T cell response of κ knock-out (κ−/−) pups resulting from various crosses and foster nursings. These systems allowed control of physiologic transmission of Igκ at defined periods of ontogeny. Our data show that conventional transfer of maternal Ig via the placenta plus colostrum/milk or adoptive transfer via only the colostrum/milk were the most efficient at tolerizing Cκ-specific CD8+ responses. Surprisingly, tolerance was not detected in κ−/− pups born to κ+/− females obtained by cesarean delivery and suckled by κ−/− mothers (transplacental supply only). Tolerance, which was strong until 5 wk of age, was reversible and waned with the decrease of Igκ serum concentration. Depletion of CD4+ T cells at the time of Cκ peptide immunization abolished the tolerance of Cκ-specific CD8+ T cells. These data suggest that an oral supply of Ig is very efficient at inducing and maintaining tolerance of Cκ-specific CD8+ T cells, at least for several weeks after birth, and that suppression rather than deletion is responsible for this tolerance. In addition, they strengthen the view that tolerance of CD8+ T cells to a soluble Ag is never permanently acquired even if it is present in large quantities during ontogeny.

Staphylococcal enterotoxin B-induced T-cell anergy is mediated by regulatory T cells

Naive T cells mount a vigorous proliferative response to superantigen (SAg) stimulation in vivo. The proliferative response is followed by a partial deletion of responder T cells. Part of the deletion process has recently been attributed to the action of regulatory cytotoxic T cells that recognize major histocompatibility complex (MHC) class I-associated antigen receptor determinants on the target cell surface. Responder T cells that survived the SAg response were found to be incapable of generating a secondary proliferative response to a SAg challenge. We show here that this 'anergy' is enforced by CD8-positive regulatory suppressive T cells. These regulatory cells inhibit cell division of preactivated T cells but not the Sag response of naive T cells. Regulatory T cells are not generated in the presence of cyclosporin A and, once activated, become inactivated or deleted when restimulated in the presence of this immunosuppressive drug.

Repertoire Analysis of CD8+ T Cell Responses to Minor Histocompatibility Antigens Involved in Graft-Versus-Host Disease

Graft-vs-host disease (GVHD) is a major complication of allogeneic bone marrow transplantation. Experimentally, lethal GVHD can be induced in MHC-matched strain combinations differing in expression of multiple minor histocompatibility Ags (miHA). Recently, the GVHD potential of C57BL/6By (B6) T cells in irradiated BALB.B (both H2b) and related CXB recombinant inbred strains of mice has been studied to determine the scope of the response to miHA in vivo and how it compared with CTL responses to immunodominant miHA in vitro. The GVHD response in these strain combinations appeared to be limited to a few Ags, yet there was no correlation of these miHA with that of in vitro CTL responses. To further investigate the role of CD8+ T cells in GVHD, we analyzed positively selected miHA-specific donor CD8+ thoracic duct lymphocytes (TDL) collected from irradiated BALB.B and CXBE mice, 5 to 6 days after transplantation of B6 T cells. Flow cytometric analysis of B6→BALB.B TDL did not indicate expansion of any particular TCR Vβ family, whereas Vβ10 and Vβ14 families were significantly expanded in the B6->CXBE TDL. However, PCR-based complementarity-determining region 3 size spectratyping revealed overlapping involvement of donor Vβ1, 6, 8, 9, 10, and 14 families in both BALB.B and CXBE recipients and unique utilization of the Vβ4 family in BALB.B mice, suggesting oligoclonal T cell responses to a limited number of miHA. In addition, the injection of CD8+Vβ14+ B6 T cells into irradiated BALB.B and CXBE mice induced lethal GVHD, confirming the involvement of miHA-specific T cells within an individual Vβ family.

Autoantibodies to T-lineage cells in aged mice

Aging is accompanied by a marked decline in protective immune function. This loss of effective immunity is largely due to alterations in the T-cell compartment. There are major impairments in both the production of new T-cells within the thymus and in the functions of mature T-cells in peripheral lymphoid organs. The mechanism(s) underlying this age-related decline in T-lineage cells is not clear. Here, we demonstrate that aging is accompanied by the appearance of appreciable titers of anti-T-lineage autoantibodies. The autoantibodies, which are exclusively of the IgM class, begin to appear at 1 year of life and are universally found in the sera of 2-year-old mice. Among thymocytes, all CD4/CD8 subsets reacted with the autoantibodies, with the CD4+8+ subset showing the greatest reactivity. The autoantibodies also bound to resting peripheral CD4+ and CD8+ cells. Following activation with either anti-CD3 or with TCR-independent stimulators, reactivity to peripheral T-cells was diminished, suggesting that the determinants recognized by the autoantibodies are downregulated in response to activation signals. Lastly, thymocytes freshly isolated from old, but not young, mice have IgM antibodies bound to their surfaces. Thus, circulating autoantibodies in old mice have access to the thymus and bind to thymocytes in situ. These results lead to the proposal that the presence of anti-T-lineage autoantibodies in vivo interferes with normal T-cell development and/or function in aged animals.

Dipeptidyl Peptidase I and Granzyme A Are Coordinately Expressed During CD8+ T Cell Development and Differentiation

Dipeptidyl peptidase I (DPPI) is a granule protease that plays a requisite role in processing the proenzyme form of the CTL granule serine proteases (granzymes). This study assesses DPPI mRNA and enzyme expression during T lymphocyte ontogeny and CTL differentiation. The most immature CD3−CD4−CD8− thymocytes were found to express >40-fold higher levels of DPPI mRNA, although levels of DPPI enzymatic activity in CD3−CD4−CD8− thymocytes were only modestly higher than those seen for CD4+CD8+ or CD4+CD8− thymocytes. More mature CD8+CD4− thymocytes and CD8+ splenocytes expressed significantly higher levels of DPPI mRNA and enzymatic activity than CD4+CD8+ or CD4+CD8− thymocytes. Granzyme A mRNA expression was observed in DPPI expressing CD3−CD4−CD8− and CD8+CD4− thymocytes and was also observed in CD8+CD4− splenocytes; however, expression was not observed in CD4+CD8+ or CD4+CD8− thymocytes. Both DPPI mRNA and granzyme A mRNA expression in CD8+ T cells decreased to very low or undetectable levels during the first 48 h after allostimulation in MLCs. However, peak levels of both DPPI and granzyme A expression were observed later in the course of CD8+ T cell responses to alloantigen, with DPPI mRNA expression peaking on either day 3 or day 4 and granzyme A expression peaking at the end of a 5-day MLR. These data indicate that DPPI is expressed at all stages of T cell ontogeny and differentiation in which granzyme A mRNA is detected; consequently, DPPI appears to be available for the processing and activation of granzyme A during both CD8+ T cell development and differentiation.

Spectratyping of TCR Expressed by CTL-Infiltrating Male Antigen (HY)-Disparate Allografts

Minor histocompatibility Ags (HA) play prominent roles in stimulating allograft rejection and are recognized by CTLs that mediate this process. There is limited information regarding the sequences of minor HA peptides and the diversity of minor HA-specific TCRs. In the case of the male minor HA (HY), a peptide presented by H2Db molecules has been sequenced. We have used spectratyping to study the diversities of Vβ usage and β complementarity-determining region 3 (CDR3) lengths of TCRs expressed by CTLs that infiltrate HY-disparate skin allografts during rejection. Spectratyping of RNA from second- and third-set male allografts on CD4-depleted, female recipients showed a reduction in Vβ usage and β CDR3 length diversity with prominent representation of Vβ8 genes. CDR3 sequences, as a group, were characterized by net negative charges resulting from negatively charged residues at positions 5–6 and 10–11. The effects of in vivo anti-Vβ8 Ab treatment on rejection of second-set male allografts were investigated. This Ab treatment had no effect on allograft rejection time and resulted in increased Vβ7 usage in recipients with complete Vβ8 depletion. More interestingly, the net charges of β CDR3s derived from Vβ8-depleted recipients were altered by the inclusion of positively charged and polar residues at positions 4–6. These results indicate that Vβ-specific T cell depletion has no effect on HY-disparate allograft survival, but it alters Vβ usage and changes the characteristics of β CDR3s that facilitate class I:peptide recognition.

Macrophage phenotype in mice deficient in both macrophage-colony-stimulating factor (op) and apolipoprotein E

Mice deficient in both macrophage-colony-stimulating factor (M-CSF, op) and apolipoprotein E (apoE) have elevated cholesterol levels but are protected from atherosclerosis. To assess the contribution of macrophage (Mphi) phenotypic heterogeneity and scavenger receptor (SR-A) expression to this seeming paradox, we characterized the Mphi phenotype by immunohistochemistry in these animals. Lesion size was determined in animals fed a chow or Western-type diet, and lipoprotein clearance studies were performed in vivo. Op0/E0 mice have fourfold smaller aortic root lesions than op2/E0 animals despite 2.5-fold higher total plasma cholesterol levels. Mphis in atherosclerotic lesions of op2/E0 mice constitute a predominantly recruited and M-CSF-dependent population. In addition, Mphis in different locations in plaques show phenotypic heterogeneity. SR-A expression in op0/E0 mice is reduced in proportion to the decrease in Mphi numbers, and M-CSF is thus not an essential requirement for SR-A expression in vivo. M-CSF-deficient mice degrade injected AcLDL , showing an adequate level of SR-A activity present in vivo. In contrast, beta-VLDL clearance in op0/E0 mice is decreased, implicating monocytes/Mphis in its catabolism. There is prominent lipid accumulation in op2/E0 Kupffer cells and hepatocytes but not in M-CSF-independent Kupffer Mphis from op0/E0 mice. SR-A, while abundantly expressed on both Kupffer cells and sinusoidal endothelial cells in op2/E0 mice, remains mainly on sinusoidal endothelial cells in op0/E0 mice. This may explain preservation of SR-A activity in these animals. Our findings clearly illustrate the importance of both M-CSF and M-CSF-dependent monocytes/Mphis in maintaining cholesterol homeostasis and in atherogenesis.

Hemopoiesis in long-term stroma-dependent cultures from lymphoid tissue: production of cells with myeloid/dendritic characteristics

A long-term stroma-dependent culture system (LTC) has been developed which continuously produces hemopoietic cells providing an in vitro system for the study of cell differentiation. These nonadherent cell populations contain a large subpopulation of dendritic cells (DC). LTC producing DC were easily generated from spleen, but could also be established from bone marrow (BM) and lymph node with less success. It was difficult to establish DC-producing LTC from thymus. The properties of splenic and thymic stroma have been compared. Spleen stroma developed more complicated networks of fibroblasts, endothelial cells, macrophages, and DC. Thymic stromal monolayers were dominated by epithelial cells and fibroblasts, with a lower proportion of macrophages and endothelial cells. They had a relatively sparse structure of cell networks compared with spleen stroma. Cells with dendritiform morphology first appeared in cultures by 2-3 wk. The majority of cells produced were large cells which expressed DC-specific cell surface markers, major histocompatibility complex (MHC) Class II molecules, and the CD80/CD86(B7) costimulator. A high proportion of cells also expressed myeloid cell markers. No T or B lymphoid cells or granulocytes were present in the cultures. LTC continued to produce nonadherent cells resembling myeloid/DC for long periods, even after passage of stromal cells and stem cells at about 3-4 mo. after culture establishment. The LTC system offers potential to study the in vitro differentiation of myeloid/DC.

Cutting Edge: Infection of Mice Lacking the Common Cytokine Receptor γ-Chain (γc) Reveals an Unexpected Role for CD4+ T Lymphocytes in Early IFN-γ-Dependent Resistance to Toxoplasma gondii

Mice lacking the common cytokine receptor γ-chain (γc) gene exhibit defective development of NK cells and CD8+ T cells and greatly diminished production of IFN-γ. Because resistance of SCID mice to Toxoplasma gondii requires IL-12-dependent IFN-γ production by NK cells, we expected that γc-deficient mice would succumb rapidly to the parasite. Surprisingly, however, most γc-deficient mice survived the acute phase of T. gondii infection. As in wild-type mice, this resistance required IL-12 and IFN-γ; nevertheless, whereas wild-type mice depleted of CD4+ T cells survived, anti-CD4+ treated γc-deficient mice displayed diminished production of IFN-γ and all succumbed to acute infection. These data not only reveal a role for CD4+ T lymphocytes in IFN-γ-dependent host defense but also establish SCID and γc-deficient mice as powerful complementary tools for assessing the function of NK vs CD4+ T cells in immunopathophysiologic responses.

LPAM-1 (integrin alpha 4 beta 7)-ligand binding: overlapping binding sites recognizing VCAM-1, MAdCAM-1 and CS-1 are blocked by fibrinogen, a fibronectin-like polymer and RGD-like cyclic peptides

The alpha 4 integrin LPAM-1 (alpha 4 beta 7) mediates lymphocyte attachment within the extracellular matrix (ECM) by adhering to the connecting segment (CS)-1 site of fibronectin (FN). Here we reveal that very late antigen (VLA)-4 LPAM-1+ T cell lymphoma TK-1 cells bind via LPAM-1 to multiple copies of the RGD sequence engineered within an FN-like polymer. Further, the small conformationally restrained RGD-like cyclic peptides 1-adamantaneacetyl-Cys-Gly-Arg-Gly-Asp-Ser-Pro-Cys and Arg-Cys-Asp-thioproline-Cys inhibit the adhesion of TK-1 cells to immobilized CS-1 peptide, and to endothelial counterreceptors for LPAM-1, namely mucosal addressin cell adhesion molecule (MAdCAM)-1 and vascular cell adhesion molecule (VCAM)-1. Spontaneous adhesion of the VLA-4- LPAM-1+ B lymphoma cell line RPMI 8866 to CS-1 was likewise inhibited, confirming a previously undocumented ability of LPAM-1 to recognize the RGD tripeptide. The RGD-binding site in LPAM-1 either overlaps or is identical to sites required for interaction with MAdCAM-1, VCAM-1, and the CS-1. The binding of LPAM-1 and VLA-4 to RGD-containing ligands may have relevance in vivo given that fibrinogen at physiological concentrations is able to partially block the binding of TK-1 cells to MAdCAM-1. Hence fibrinogen and other vascular RGD-containing proteins may have mild anti-inflammatory activity required for maintaining effective homeostasis, analogous to the anti-thrombogenic activity of the vascular endothelium.

Association between leukocyte infiltration and development of glomerulosclerosis in experimental lupus nephritis

Mice with chronic graft-versus-host disease (GvHD) induced by injection of DBA/2 lymphocytes into (DBA/2 x C57BL/10) F1 hybrids (DBA/2 GvHD) develop a lupus-like glomerulonephritis with global glomerulosclerosis 12 weeks after induction of the disease. In two other strain combinations with similar H-2 incompatibilities [BALB/c into BALB/c x BL10 (BALB/c GvHD) and BALB.D2 into BALB.D2 x BL10 (BALB.D2 GvHD)], GvHD induction leads to lupus nephritis without global glomerulosclerosis. This study investigated the identity of kidney-infiltrating leukocytes and their involvement in the development of glomerulosclerosis in these three strain combinations. In mice with DBA/2 GvHD, a significant increase in glomerular CD11a-positive cells was found 4 weeks after disease induction. Mice with BALB/c or BALB.D2 GvHD did not show an increase in glomerular CD11a-positive cells at any time point. In the interstitium, CD11a-positive cells were observed 4 weeks after disease induction only in mice with DBA/2 GvHD. In mice with BALB.D2 GvHD, no increase was found in interstitial CD11a-positive cells. In mice with BALB/c GvHD, interstitial CD11a-positive cells were found from week 4 onward. Further immunohistochemical analysis of the glomerular CD11a-positive cells in mice with DBA/2 GvHD showed that these cells were neither polymorphonuclear leukocytes (PMN), nor CD3-positive (T cells), B220-positive (B cells), or F4/80-positive (macrophages). They were all CD45-positive (leukocytes) and MHC class II-positive. In conclusion, we have shown in this model of chronic lupus nephritis that glomerular influx of as yet unidentified CD11a-positive leukocytes is associated with the development of glomerulosclerosis.

Antibody to Pneumocystis carinii protects rats and mice from developing pneumonia

Well-proven mouse and rat models were used to show that polyclonal antisera to Pneumocystis carinii protect against P. carinii pneumonia. Antibodies were obtained from animals that were allowed to recover from severe P. carinii pneumonia after immunosuppression had been stopped and which then were given a booster injection of P. carinii from the same animal species. Mice immunosuppressed with corticosteroids or antibodies to L3T4+ lymphocytes (which are comparable to CD4 cells of humans) and transtracheally inoculated with mouse P. carinii did not develop P. carinii pneumonia if they were passively immunized with antiserum, while mice immunosuppressed and inoculated by identical procedures but not given antibodies developed severe infections. Rats immunosuppressed with corticosteroids and inoculated with rat P. carinii had less severe infections if they were given rat anti-P. carinii antisera. The polyclonal antisera developed in mice provided greater protection for the mice than the polyclonal rat antisera did for the rats; however, the potencies and compositions of the antisera were not quantitated and probably differed. Since both rats and mice can be protected from P. carinii infections with polyclonal antisera, it may be possible to develop vaccines that will elicit protective antibodies in humans.

Expression, purification, and characterization of a murine CD4 fragment containing the first two N-terminal domains

CD4 is a membrane glycoprotein on T lymphocytes that binds to the same peptide:major histocompatibility complex (MHC) class II molecules recognized by the antigen-specific T cell receptor (TcR). Recent evidence supports the importance of coaggregation of CD4 and TcR for effective T cell activation. Here, we report that a transfected Chinese hamster ovary (CHO) cell line expressing a murine CD4 fragment containing the first two N-terminal domains secretes both monomeric molecules and disulfide-linked multimers. Elimination of the predicted N-linked glycosylation site at residue 161 that is next to the fourth cysteine does not affect the formation of interchain disulfide bonds. N-Terminal amino acid sequencing of the purified CD4 fragment demonstrates that the leader signal sequence is properly cleaved off the expressed protein. Circular dichroism studies suggest that both monomeric and disulfide-linked proteins are folded as primarily beta-sheet.

Induction of airway mucus production By T helper 2 (Th2) cells: a critical role for interleukin 4 in cell recruitment but not mucus production

Airway inflammation is believed to stimulate mucus production in asthmatic patients. Increased mucus secretion is an important clinical symptom and contributes to airway obstruction in asthma. Activated CD4 Th1 and Th2 cells have both been identified in airway biopsies of asthmatics but their role in mucus production is not clear. Using CD4 T cells from mice transgenic for the OVA-specific TCR, we studied the role of Th1 and Th2 cells in airway inflammation and mucus production. Airway inflammation induced by Th2 cells was comprised of eosinophils and lymphocytes; features found in asthmatic patients. Additionally, there was a marked increase in mucus production in mice that received Th2 cells and inhaled OVA, but not in mice that received Th1 cells. However, OVA-specific Th2 cells from IL-4-deficient mice were not recruited to the lung and did not induce mucus production. When this defect in homing was overcome by administration of TNF-alpha, IL-4 -/- Th2 cells induced mucus as effectively as IL-4 +/+ Th2 cells. These studies establish a role for Th2 cells in mucus production and dissect the effector functions of IL-4 in these processes. These data suggest that IL-4 is crucial for Th2 cell recruitment to the lung and for induction of inflammation, but has no direct role in mucus production.

Development of Natural Killer Cells, B Lymphocytes, Macrophages, and Mast Cells From Single Hematopoietic Progenitors in Culture of Murine Fetal Liver Cells

We have recently established a clonal culture system that supports the growth of immature natural killer (NK) cells from murine fetal thymocytes. We now describe a culture system for mixed NK cell colony formation from single lymphohematopoietic progenitors. When Sca-1+c-kit+ fetal liver cells were cultured in methylcellulose media with interleukin (IL)-2, IL-7, IL-11, and steel factor (SF ), we found mixed colonies consisting of diffuse small round cells characteristic of immature NK cells and other types of cells. The single cell origin of the mixed colonies was established by micromanipulation. Individual mixed colonies derived from single cells were characterized by flow cytometric analysis and May-Grünwald Giemsa staining. All mixed colonies contained Thy-1+B220− cells, which can differentiate to mature NK cells in fetal thymus organ culture. Most of the colonies contained B220+ B-lineage cells and macrophages, and some contained mast cells. IL-1α and IL-3, which have previously been shown to inhibit the T- and B-cell potentials of blast colonies, suppressed the formation of mixed NK cell colonies. The clonal culture assay presented here may be useful in analysis of the developmental pathway and commitment of NK cells from multipotential progenitors.

The immune system preferentially clears Theiler's virus from the gray matter of the central nervous system

Infection of susceptible strains of mice with Daniel's (DA) strains of Theiler's murine encephalomyelitis virus (DAV) results in virus persistence in the central nervous system (CNS) white matter and chronic demyelination similar to that observed in multiple sclerosis. We investigated whether persistence is due to the immune system more efficiently clearing DAV from gray than from white matter of the CNS. Severe combined immunodeficient (SCID) and immunocompetent C.B-17 mice were infected with DAV to determine the kinetics, temporal distribution, and tropism of the virus in CNS. In early disease (6 h to 7 days postinfection), DAV replicated with similar kinetics in the brains and spinal cords of SCID and immunocompetent mice and in gray and white matter. DAV RNA was localized within 48 h in CNS cells of all phenotypes, including neurons, oligodendrocytes, astrocytes, and macrophages/microglia. In late disease (13 to 17 days postinfection), SCID mice became moribund and permitted higher DAV replication in both gray and white matter. In contrast, immunocompetent mice cleared virus from the gray matter but showed replication in the white matter of their brains and spinal cords. Reconstitution of SCID mice with nonimmune splenocytes or anti-DAV antibodies after establishment of infection demonstrated that both cellular and humoral immune responses decreased virus from the gray matter; however, the cellular responses were more effective. SCID mice reconstituted with splenocytes depleted of CD4+ or CD8+ T lymphocytes cleared virus from the gray matter but allowed replication in the white matter. These studies demonstrate that both neurons and glia are infected early following DAV infection but that virus persistence in the white matter is due to preferential clearance of virus from the gray matter by the immune system.

Analysis of susceptibility of NOD mice to spontaneous and experimentally induced thyroiditis

Beside diabetes, non-obese diabetic (NOD) mice develop sporadic lymphoid infiltration of the thyroid gland, mimicking Hashimoto's thyroiditis. We have examined the prevalence of those manifestations in NOD mice, the influence of the major histocompatibility complex (MHC) and the association with autoantibodies. The incidence at 1 year is of 14.3% in wild-type NOD mice versus 19.6% in congenic NOD.H2k mice. The moderate, but statistically significant difference, based on the analysis of 161 NOD and 169 NOD.H2k mice, suggests that MHC genes partially control spontaneous NOD thyroiditis. Autoantibodies against thyroglobulin (Tg) are mouse specific and their presence correlates closely with thyroiditis. The strong correlation between cellular and humoral anomalies therefore resembles Hashimoto's thyroiditis. NOD and NOD.H2k mice actively immunized against Tg develop severe chronic lesions with epithelium necrosis and interstitial tissue fibrosis. Most interestingly, those lesions do not regress spontaneously as in CBA/J mice. Paradoxically, the response to Tg of lymph node cells from NOD mice is weaker both in proliferation and cytokine production. The defect is most evident for interferon-gamma-producing T cells and is reflected in the marked deficit in IgG2a antibodies. Thus a moderate anti-Tg response seems to favor chronicity of thyroiditis. In conclusion, NOD and NOD.H2k mice offer a unique opportunity of analyzing the factors leading to immune chronicity in a genetic context which promotes autoimmune endocrinopathies.

Oral administration of antigen does not influence the proliferation and IFN-γ production of responsive CD8+ T cells but enables to establish T cell clones with different lymphokine production profile

Feeding of a whole casein diet, which abolished the α(s1)-casein-specific proliferation and IFN-γ productivity of CD(4+) T cells, did not affect the proliferative response of CD8(+) T cells with regard to the antigen dose response, cell dose response, kinetics of the proliferation and epitope specificity, as well as IFN-γ production. To assess the characteristics of the CD8(+) T cells, we established α(s1)-casein-specific CD8(+) T cell clones from both casein-fed and control mice. The established clones produced different amount of IFN-γ and IL-10, and one clone derived from the casein-fed mice produced a remarkable amount of IL-10. The clones from casein-fed mice produced considerable amounts of TGF-β, while those from control mice produced only small amounts. The possible role of CD8(+) T cells in oral tolerance is discussed.

Immunohistological study of lesions induced by Porphyromonas gingivalis in a murine model

A previous study used a mouse model to demonstrate protection after challenge with Porphyromonas gingivalis ATCC 33277. In the present study, this same model was used to determine the phenotype of cells recruited into the lesions during the course of the protective immune response after immunization with this periodontal pathogen. BALB/c mice were immunized with 100 micrograms of P. gingivalis outer membrane antigens per mouse weekly for 3 weeks followed by challenge with live organisms 3 weeks after the final immunization. Hematoxylin and eosin-stained sections showed inflammatory infiltrates in all lesions from control (immunized with adjuvant only) and immunized mice. The lesions developed central necrotic cores surrounded by neutrophils, phagocytic macrophages and lymphocytes. Neutrophils were the predominant cells in the lesions 1 day after challenge with significantly more in immunized than control mice. Acid phosphatase and nonspecific esterase-positive macrophages were detected at day 4 and became the predominant cells in the healing lesions. CD4- and CD8-positive T-cells were present from day 1, and while numbers increased over time, there were no significant differences in control or immunized mice. When mice were depleted of CD4 or CD8 cells prior to immunization with P. gingivalis, fewer neutrophils were found in the lesions 1 day after challenge compared with undepleted immunized mice. Acid phosphatase and nonspecific esterase-positive macrophages were not affected by T-cell depletion. The results suggest that the P. gingivalis-induced lesion in immunized BALB/c mice is consistent with a strong innate immune response involving the recruitment of neutrophils in the first instance which may be under the control of T cells. This is followed by the infiltration of phagocytic macrophages which are involved in the healing process and do not appear to be regulated by T cells.

The migratory behavior of murine CD4+ cells of memory phenotype

Lymphocyte differentiation is connected with profound alterations in the migratory pattern of lymphocytes. Whereas naive cells predominantly recirculate through lymphoid tissues, activated lymphocytes acquire an increased preference for immigration into non-lymphoid tissues and a reduced capacity for recirculation via high endothelial venules (HEV). A variety of data had indicated that memory-related subpopulations of cells in man and sheep, classified by the low expression of the CD45RA isotype, also lack the capacity to recirculate via HEV. However, recent data in the rat called these results into question. We therefore analyzed the migration properties of murine CD4+ T cell subpopulations defined by several markers used to distinguish memory from naive CD4+ cells in mice, namely CD45RB, L-selectin and CD44. Our data clearly show that the majority of putative memory cells expressing either low levels of CD45RB, low levels of L-selectin or high levels of CD44 display a strongly reduced capacity for direct entry into lymphoid tissues, including the spleen, from the blood stream. The accumulation in peripheral lymph nodes is further reduced by treatment with anti-L-selectin antibody, which blocks their entry via HEV. This indicates that memory CD4+ T cells are not excluded from crossing lymph node HEV, and that the numbers of cells entering the node via this route exceed the numbers entering via the afferent lymph, at least in the absence of local inflammation. Concomitantly, a strongly enhanced localization of cells of the memory phenotype is observed in lung and liver as compared with naive cells. Trafficking to specific sites such as skin or gut mucosa is not a prominent feature of the total population of memory cells. The trafficking to lung and liver and an increased ability to bind to dendritic cells, demonstrable in in vitro adhesion assays, suggest a more sessile phenotype of most memory cells. With respect to these properties, memory cells have a surprizing similarity to fully activated lymphocytes.

Spermine induces maturation of the immature intestinal immune system in neonatal mice

BACKGROUND

In mice, immunological adaptation of the gut to microbial and nutritional antigens occurs at weaning in parallel with biochemical and morphological maturation. Because oral administration of spermine to neonatal rats has been shown to induce biochemical and morphological maturation, we investigated whether spermine also affects maturation of the mucosal immune system.

METHODS

Swiss mice 7, 12, and 27 days old were given spermine orally (0.5 mumol/g body weight) during 3 days. Intestinal length was measured, and lactase and sucrase activities were determined. The phenotype of intraepithelial and lamina propria lymphocytes was assessed by FACS analysis using markers for CD3, TCR alpha beta, TCR gamma delta, CD4, CD8 alpha, CD8 beta, CD5, CD18, CD54, and CD49d.

RESULTS

Similar to what occurs during natural development, spermine treatment of neonatal mice increased intestinal length, decreased lactase activity, and increased sucrase activity. The percentage of intraepithelial lymphocytes expressing TCR alpha beta, CD4, CD5, and CD54, as well as the levels of expression of these antigens, increased after spermine treatment on day 12, similarly to natural maturation. The increase in expression of CD3, TCR gamma delta, CD18, and CD49d did not reach statistical significance. No effect was observed on CD8 expression. The phenotype of lamina propria lymphocytes was not affected. Spermine administration to 7- and 27-day-old mice had no effect on the phenotype of either intraepithelial or lamina propria lymphocytes.

CONCLUSIONS

Oral spermine administration to neonatal mice induced, in parallel with biochemical maturation, precocious maturation of the murine intestinal immune system and particularly affected differentiation of the intraepithelial lymphocyte population.

Role of T cells in the pathogenesis of autoimmune lacrimal gland disease in MRL/Mp-lpr/lpr mice

PURPOSE

MRL/Mp-lpr/lpr mice (MRL/lpr) spontaneously develop an autoimmune disease, including lacrimal gland lesions, which are a model for Sjögren's syndrome. Target organ lesions in MRL/lpr mice are composed largely of CD4+ T cells, and treatment with monoclonal antibodies (mAb) against CD4 improves in the systemic autoimmune disease but not the lacrimal gland inflammation. In anti-CD4 mAb-treated MRL/lpr mice, the lacrimal gland lesions are composed largely of CD8+ T cells. The effects of depletion of: (1) all T cells; (2) both CD4+ and CD8+ T cells, and (3) only CD8+ T cells on the lacrimal gland disease were investigated.

METHODS

MRL/lpr mice underwent neonatal thymectomy and were treated with weekly injections of 6 mg of anti-Thy 1 mAb from age one week until sacrifice at age five months. Control nonthymectomized mice underwent similar treatment with either saline or normal rat immunoglobulin (rIg) injections. In a second experiment, MRL/lpr mice were treated with weekly injections of either: (1) 2 mg anti-CD4 mAb and 5 mg anti-CD8; or (2) 5 mg anti-CD8 alone. Control mice underwent similar treatment with either saline or rIg injections.

RESULTS

Combined treatment with neonatal thymectomy and anti-Thy 1 mAb was effective in reducing the lacrimal gland disease in both frequency (50% > or = grade 3 vs. 100% in controls, P < 0.002) and extent (median 0% of lacrimal gland area involved by inflammation vs. 14.8% in controls; P = 0.01). Combined anti-CD4 and anti-CD8 therapy also was effective in reducing the lacrimal gland disease in terms of frequency (25% grade 3 vs. 93% in controls; P = 0.002) and extent (median 0% of lacrimal gland involved by inflammation vs. 12.9% in controls; P = 0.0005). Treatment with anti-CD8 mAb therapy alone was ineffective. The systemic autoimmune disease was also improved by T cell depletion and by combined anti-CD4 and anti-CD8 mAb therapy but not by anti-CD8 mAb therapy alone.

CONCLUSIONS

Suppression of both CD4+ and CD8+ T cells is required to suppress lacrimal gland inflammation in MRL/lpr mice.

T cell tolerance to kappa light chain (L kappa): identification of a naturally processed self-C kappa-peptidic region by specific CD4+ T cell hybridomas obtained in L kappa-deficient mice

In contrast to H-2d kappa light chain-deficient mice (kappa-/-), BALB/c (kappa+/+) mice fail to respond to kappa light chains (L kappa). This suggests that C kappa-specific T cells are tolerant to this self-antigen in kappa+/+ mice. To get insights into the cellular and molecular basis of this tolerance, we first characterized the presented L kappa-derived C kappa-peptidic region(s). Among a library of overlapping peptides spanning the whole C kappa sequence, only three consecutive peptides are recognized by CD4+ T cell hybridomas obtained in L kappa-immunized kappa-/- mice. This C kappa-peptidic region, which is also the only one containing the I-Ed-binding consensus motif, is immunogenic since it is able to prime lymph node cells of kappa-/- mice to subsequent in vitro proliferative response to either L kappa or kappa+/+ APC. Conversely, no kappa+/+ T cell proliferation is observed under the same conditions. Activation of our hybridomas by cells from central and peripheral lymphoid tissues reveals that this C kappa region is naturally expressed on BALB/c kappa+/+ APC. In addition to B cells, macrophages and dendritic cells are able to present this region. Taken together our data suggest that the described self-C kappa region is implicated in the C kappa-specific CD4+ T cell tolerization in BALB/c mice.

Murine salmonellosis studied by confocal microscopy: Salmonella typhimurium resides intracellularly inside macrophages and exerts a cytotoxic effect on phagocytes in vivo

Salmonella typhimurium is considered a facultative intracellular pathogen, but its intracellular location in vivo has not been demonstrated conclusively. Here we describe the development of a new method to study the course of the histopathological processes associated with murine salmonellosis using confocal laser scanning microscopy of immunostained sections of mouse liver. Confocal microscopy of 30-micron-thick sections was used to detect bacteria after injection of approximately 100 CFU of S. typhimurium SL1344 intravenously into BALB/c mice, allowing salmonellosis to be studied in the murine model using more realistic small infectious doses. The appearance of bacteria in the mouse liver coincided in time and location with the infiltration of neutrophils in inflammatory foci. At later stages of disease the bacteria colocalized with macrophages and resided intracellularly inside these macrophages. Bacteria were cytotoxic for phagocytic cells, and apoptotic nuclei were detected immunofluorescently, whether phagocytes harbored intracellular bacteria or not. These data argue that Salmonella resides intracellularly inside macrophages in the liver and triggers cell death of phagocytes, processes which are involved in disease. This method is also applicable to other virulence models to examine infections at a cellular and subcellular level in vivo.

Differential T cell receptor-mediated signaling in naive and memory CD4 T cells

Naive and memory CD4 T cells differ in cell surface phenotype, function, activation requirements, and modes of regulation. To investigate the molecular bases for the dichotomies between naive and memory CD4 T cells and to understand how the T cell receptor (TCR) directs diverse functional outcomes, we investigated proximal signaling events triggered through the TCR/CD3 complex in naive and memory CD4 T cell subsets isolated on the basis of CD45 isoform expression. Naive CD4 T cells signal through TCR/CD3 similar to unseparated CD4 T cells, producing multiple tyrosine-phosphorylated protein species overall and phosphorylating the T cell-specific ZAP-70 tyrosine kinase which is recruited to the CD3zeta subunit of the TCR. Memory CD4 T cells, however, exhibit a unique pattern of signaling through TCR/CD3. Following stimulation through TCR/CD3, memory CD4 T cells produce fewer species of tyrosine-phosphorylated substrates and fail to phosphorylate ZAP-70, yet unphosphorylated ZAP-70 can associate with the TCR/CD3 complex. Moreover, a 26/28-kDa phosphorylated doublet is associated with CD3zeta in resting and activated memory but not in naive CD4 T cells. Despite these differences in the phosphorylation of ZAP-70 and CD3-associated proteins, the ZAP-70-related kinase, p72syk, exhibits similar phosphorylation in naive and memory T cell subsets, suggesting that this kinase could function in place of ZAP-70 in memory CD4 T cells. These results indicate that proximal signals are differentially coupled to the TCR in naive versus memory CD4 T cells, potentially leading to distinct downstream signaling events and ultimately to the diverse functions elicited by these two CD4 T cell subsets.

Cytokines in the induction and expression of T-cell-mediated granuloma formation and protection in the murine model of listeriosis

Lymphocyte-mediated inflammation is a hallmark of autoimmune diseases, such as multiple sclerosis. Crohn's disease, rheumatoid arthritis and sarcoidosis. However, this type of inflammation probably developed under evolutionary pressure from pathogenic microorganisms, such as mycobacteria and other intracellular infective agents. One such pathogen, the gram-positive bacterium Listeria monocytogenes (L. monocytogenes), induces a cascade of tissue alterations that ultimately results in the eradication of the bacteria associated with a granulomatous response. Consequently, murine listeriosis has been established as a model to analyze not only T-cell-dependent antibacterial protection but also T-cell-mediated mononuclear inflammation in parenchymal organs. Extensive studies of the molecular basis of the latter phenomenon led to the conclusion that the most decisive step from non-specific microabscess formation to granulomatous inflammation is the activation of non-specifically invading CD4+ T cells, which results in high local concentrations of TNF-alpha and IFN-gamma in the presence of IL-2. This in turn induces CD11b-independent mechanisms of intraparenchymal monocyte accumulation. Because any attempt to neutralize the effects of TNF-alpha and IFN-gamma to modulate T-cell-mediated inflammation will also dramatically decrease host resistance, other anti-inflammatory strategies based on the modulation of TNF-alpha and IFN-gamma-induced mechanisms of monocyte accumulation must be developed. Recalling the classical work by Dienes & Schoenheit on the induction of bacterial allergies (1), the cytokine phenotype of granuloma formation also has implications as regards the most potent adjuvant environment for the development of a T-cell response. The murine listeriosis model is the basis for all conclusions in this article on the role of cytokines in the induction and expression of T-cell-mediated inflammation and, as we will show, promises to yield still more insights into the rational design of vaccines.

Memory T cell tolerance to superantigens is not due to increased susceptibility to apoptosis

Naive (virgin) and memory T lymphocytes differ markedly in their response to superantigens (SAg). When cultured with the SAg staphylococcal enterotoxin B (SEB), virgin but not memory CD4(+) T cells proliferate and secrete lymphokines. Memory cells do express increased levels of activation markers after interaction with SEB, which suggests that the cells are not ignorant of the SAg. In this report, we have considered whether SEB, rather than activating memory cells, promotes their death by apoptosis. Our results indicate that while in vivo exposure to SEB induces apoptosis, there is no greater level of cell death in the memory cell population relative to virgin cells. Further, elimination of the Fas-mediated cell death pathway does not permit memory cells to be stimulated by SEB. Memory T cells from either Fas-expressing or Fas-deficient (MRL-lpr/lpr) mice are hyporesponsive to SEB. Blockade of Fas/Fas-ligand interactions by a Fas-Fc chimeric protein does not permit BALB/c memory cells to proliferate upon culture with SEB. These results provide evidence that the failure of memory T cells to respond to SEB is not due to cell death and that inactivation (anergy) is the likely fate of these cells when they encounter SEB.

Antigenic cancer cells grow progressively in immune hosts without evidence for T cell exhaustion or systemic anergy

One enigma in tumor immunology is why animals bearing malignant grafts can reject normal grafts that express the same nonself-antigen. An explanation for this phenomenon could be that different T cell clones react to the normal graft and the malignant cells, respectively, and only the tumor-reactive clonotypes may be affected by the growing tumor. To test this hypothesis, we used a T cell receptor transgenic mouse in which essentially all CD8(+) T cells are specific for a closely related set of self-peptides presented on the MHC class I molecule Ld. We find that the tumor expressed Ld in the T cell receptor transgenic mice but grew, while the Ld-positive skin was rejected. Thus, despite an abundance of antigen-specific T cells, the malignant tissue grew while normal tissue expressing the same epitopes was rejected. Therefore, systemic T cell exhaustion or anergy was not responsible for the growth of the antigenic cancer cells. Expression of costimulatory molecules on the tumor cells after transfection and preimmunization by full-thickness skin grafts was required for rejection of a subsequent tumor challenge, but there was no detectable effect of active immunization once the tumor was established. Thus, the failure of established tumors to attract and activate tumor-specific T cells at the tumor site may be a major obstacle for preventive or therapeutic vaccination against antigenic cancer.

A primatized MAb to human CD4 causes receptor modulation, without marked reduction in CD4+ T cells in chimpanzees: in vitro and in vivo characterization of a MAb (IDEC-CE9.1) to human CD4

A Primatized anti-CD4 monoclonal antibody (MAb), CE9.1, with V-domain from cynomolgus macaque (showing 92% homology with human consensus sequence V-domains), and a human IgG1 constant region, was characterized in vitro and in vivo in chimpanzees. This MAb binds human CD4 with Kd of 1.0 nM and was also able to bind to human IgG Fc receptors (Fc gamma R). However, despite being of the IgG1 subclass, CE9.1 did not bind to complement component C1q, nor did it mediate complement-dependent cytotoxicity. Examination of T cells from a number of species showed restricted reactivity for CE9.1, recognizing only human and chimpanzee CD4. In both human and chimpanzee MLRs, it had an IC50 of about 10.0 ng/mL. Therefore, a chimpanzee in vivo model was used to characterize CE9.1, CE9.1 caused transient decrease in the number of lymphocytes bearing the CD4 receptor starting at doses of 0.3 mg/kg in an in vivo dose ranging study in one chimpanzee. This effect was reversed within approximately 7 days. In a multiple high-dose study in which 10.0 mg/kg of CE9.1 was administered at intervals of 1-3 months, there was a dramatic loss of CD4 marker with a reciprocal increase in the number of CD3+ CD8- CD4- cells. The CD4 receptor was totally undetectable on these lymphocytes for 1-2 weeks, with a gradual, but complete, reversal within 4 weeks. We interpret these observations as receptor modulation because, although there was apparent loss of CD4+ lymphocytes, an equivalent number of CD3+CD8- T lymphocytes were present in circulation in all four chimpanzees treated with 10.0 mg/kg CE9.1. Even at this high dose, only limited reduction of CD4+ T lymphocytes was observed in these animals. These observations are in sharp contrast to what has been reported in rodents or in human clinical studies using other IgG1 mAbs to human CD4. CD8 counts, although variable, remained unaffected by CE9.1 treatment. No adverse events were observed following administration of CE9.1 to chimpanzees, and there was no detectable host immune responses to the Primatized MAb.

A spontaneously arising mutation in the DLAARN motif of murine ZAP-70 abrogates kinase activity and arrests thymocyte development

Development of immature CD4+ CD8+ thymocytes into functionally mature CD4+ and CD8+ T cells is driven by selection events that require signals transduced through the T cell antigen receptor (TCR). Transduction of TCR signals in the thymus involves tyrosine phosphorylation of the protein tyrosine kinase ZAP-70 by p56(lck) and results in induction of ZAP-70 enzymatic activity. We have identified a novel, spontaneously arising point mutation within a highly conserved motif (DLAARN) in the kinase domain of murine ZAP-70 that uncouples tyrosine phosphorylation of ZAP-70 from induction of ZAP-70 kinase activity. Mice homozygous for this mutation are devoid of mature T cells because thymocyte development is arrested at the CD4+ CD8+ stage of differentiation. The developmental arrest is due to the inability of CD4+ CD8+ thymocytes to propagate TCR signals in the absence of ZAP-70 kinase activity despite tyrosine phosphorylation of TCR-associated ZAP-70 molecules.

Reconstitution of SCID mice with haemopoietic precursors: a detailed analysis of gamma delta T-cell reconstitution

A well-known characteristic of gamma delta T cells is that they are produced in waves during ontogeny, with cells expressing T-cell receptor V gamma 5 appearing early in fetal thymic ontogeny, followed by V gamma 6, then by other gamma delta T-cell types. In addition, evidence exists to suggest that the potential of haemopoietic precursors to generate different types of gamma delta T cells changes in ontogeny. We have used these observations as the basis for an extensive study of the potential for haemopoietic precursors isolated from fetal liver, neonatal spleen and adult bone marrow to reconstitute severe combined immunodeficient (SCID) mice. Mice that were reconstituted as newborns with fetal liver cells most closely resembled normal C.B-17 mice with respect to both lymphocyte numbers and subsets, while mice reconstituted with adult bone marrow had fewer cells than normal mice. This deficit spanned both T and B cells in all organs examined. Among the gamma delta T-cell subsets examined, the ability to reconstitute V gamma 4+ cells was particularly dependent on the ontogenic age of the reconstituting presursors, with fetal liver cells having the greatest capacity to generate V gamma 4+ cells, and adult bone marrow cells the least. The vast majority of the T cells produced in the reconstituted mice were of donor origin, and the level of reconstitution was found to be dependent upon some factor other than the presursor frequency.

Transcytosis of staphylococcal superantigen toxins

Staphylococcus aureus produces a set of proteins (e.g., staphylococcal enterotoxin A [SEA], SEB, toxic shock syndrome toxin 1 [TSST-1]) which act both as superantigens (SAgs) and toxins. Although their mode of action as SAgs is well understood, little is known about how they enter the body via the intestine and cause food poisoning. To examine this problem we used an in vitro culture system to study the capacity of class II MHC-negative human intestinal epithelial cells (Caco-2) to transcytose several staphylococcal toxins. We found that Caco-2 cells are capable of dose-dependent, facilitated transcytosis of SEB and TSST-1, but not SEA. We extended these studies in vivo in mice by showing that ingested SEB appears in the blood more efficiently than SEA. Our data suggest that these toxins can cross the epithelium in an immunologically intact form. These results may have important implications for the pathogenesis of food poisoning.

A Synthetic CD4-CDR3 Peptide Analog Enhances Bone Marrow Engraftment Across Major Histocompatibility Barriers

The efficacy of a synthetic peptide analog mimicking the CDR3-D1 domain of the CD4 molecule was investigated in murine models of allogeneic bone marrow engraftment after transplantation across major histocompatibility complex (MHC) barriers. A single dose of a CD4-CDR3 peptide analog was administered at the time of marrow transplantation to three different allogeneic mouse strain combinations after appropriate sublethal total body irradiation: (1) B10.BR → C57BL/6J (B6), a full allogeneic MHC difference; (2) (B6xDBA/2)F1 → (B6xCBA)F1 , a haploidentical MHC combination; and (3) B6.C-H2bm12 → B6-Ly5.2, involving only a MHC class II difference. Donor-host chimerism was assessed after 1 and 2 months posttransplantation by flow cytometric analysis of spleen and/or lymph node cells. Peptide-treated animals in all three strain combinations exhibited significantly enhanced donor lymphoid engraftment, which was similarly reflected in the total lymphocyte compartment and its T-cell (CD4+, CD8+) and B-cell subsets. In addition, peptide-treated mice in the haploidentical and MHC class II-mismatched strain combinations exhibited prolonged tolerance of both donor and syngeneic host-type tail skin grafts while rejecting third-party allogeneic grafts, thus supporting the reconstitution of immunocompetence in these chimeras. Lymphocytes from the peptide-treated haploidentical chimeric mice also displayed donor-specific tolerance upon stimulation in a one-way mixed lymphocyte reaction. In a 6-day colony-forming unit–granulocyte-macrophage (CFU-GM) assay to quantitate the level of hematopoietic cell engraftment in both the haploidentical and class II-disparate strain combinations, bone marrow cells from the peptide-treated mice exhibited significant increases in CFU-GM compared with the saline-treated control groups. Finally, early multiple treatments with the peptide after transplantation significantly enhanced donor chimerism in donor-presensitized recipient mice across the MHC class II barrier and proved to be significantly more effective than anti-CD4 monoclonal antibody treatment. These results indicate that the structure-based CD4-CDR3 peptide analog may represent a valuable approach to the inhibition of graft rejection after MHC-mismatched bone marrow transplantation.

Antigen presentation in retroviral vector-mediated gene transfer in vivo

We have examined mechanisms involved in gene transfer, protein expression, and antigen presentation after direct administration of retroviral vectors using a variety of antigen systems. We have identified transduced infiltrating cells at the injection site, and the majority of the infiltrating cells were of the monocyte/macrophage lineage. We found that the splenic dendritic cell fraction contained proviral DNA, expressed antigenic proteins, and was able to present antigens efficiently to the immune system. Furthermore, the dendritic cell fractions from retroviral vector-immunized mice were able to prime naive T cells in vitro, and adoptive transfer of in vitro-transduced dendritic cell fractions elicited antigen-specific cytotoxic T lymphocytes. These data suggest a role for dendritic cells in induction of immune responses elicited by retroviral vector-mediated gene transfer.

The oral administration of low-dose antigen induces activation followed by tolerization, while high-dose antigen induces tolerance without activation

The systemic immune response and tolerance induced by oral administration of various doses of bovine alpha s1-casein were examined, focusing on cytokine responses in this study. Spleen cells from mice fed low doses of antigen secreted interferon-gamma and interleukin-2 in response to in vitro antigen stimulation, indicating that a Th1-type response was induced. In these mice, the Th1 responses after subsequent immunization and boosting with the antigen were diminished. In the case of mice fed high doses of the antigen, secretion of Th1 cytokines was minimal, but systemic responses after subsequent immunization and boosting with the antigen were strongly inhibited. Active suppression was not observed at any dose. The results indicate that, in this system, low-dose feeding induced activation of Th1 cells followed by tolerization, while high-dose feeding induced profound tolerance without prior activation. Our results have implications for clinical application of oral tolerance to allergy and autoimmune disease.