Alpha beta T-lymphocyte depleted mice, a model for gamma delta T-lymphocyte functional studies

γδ T cells affect IL-4 production and B-cell tolerance

γδ T cells can influence specific antibody responses. Here, we report that mice deficient in individual γδ T-cell subsets have altered levels of serum antibodies, including all major subclasses, sometimes regardless of the presence of αβ T cells. One strain with a partial γδ deficiency that increases IgE antibodies also displayed increases in IL-4-producing T cells (both residual γδ T cells and αβ T cells) and in systemic IL-4 levels. Its B cells expressed IL-4-regulated inhibitory receptors (CD5, CD22, and CD32) at diminished levels, whereas IL-4-inducible IL-4 receptor α and MHCII were increased. They also showed signs of activation and spontaneously formed germinal centers. These mice displayed IgE-dependent features found in hyper-IgE syndrome and developed antichromatin, antinuclear, and anticytoplasmic autoantibodies. In contrast, mice deficient in all γδ T cells had nearly unchanged Ig levels and did not develop autoantibodies. Removing IL-4 abrogated the increases in IgE, antichromatin antibodies, and autoantibodies in the partially γδ-deficient mice. Our data suggest that γδ T cells, controlled by their own cross-talk, affect IL-4 production, B-cell activation, and B-cell tolerance.

Thy1+ NK [corrected] cells from vaccinia virus-primed mice confer protection against vaccinia virus challenge in the absence of adaptive lymphocytes

While immunological memory has long been considered the province of T- and B- lymphocytes, it has recently been reported that innate cell populations are capable of mediating memory responses. We now show that an innate memory immune response is generated in mice following infection with vaccinia virus, a poxvirus for which no cognate germline-encoded receptor has been identified. This immune response results in viral clearance in the absence of classical adaptive T and B lymphocyte populations, and is mediated by a Thy1⁺ subset of natural killer (NK) cells. We demonstrate that immune protection against infection from a lethal dose of virus can be adoptively transferred with memory hepatic Thy1⁺ NK cells that were primed with live virus. Our results also indicate that, like classical immunological memory, stronger innate memory responses form in response to priming with live virus than a highly attenuated vector. These results demonstrate that a defined innate memory cell population alone can provide host protection against a lethal systemic infection through viral clearance.

Immunological memory is a hallmark of adaptive immunity and provides the basis for our ability to become ‘immune’ to pathogens to which we have previously been exposed, and provides the basis for vaccination. For decades, the paradigm held that only the classical adaptive lymphocytes were capable of forming and maintaining protective immunological memory. Recently, several papers have shown the capacity of an innate cell population, a subset of natural killer (NK) cells, to exhibit certain aspects of immunological memory. Here we show that innate memory forms in response to infection with vaccinia virus and resides in a discrete subset of NK cells. We further demonstrate that this innate memory provides significant host protection against a subsequent systemic infection with a lethal dose of vaccinia virus, in some cases resulting in the complete clearance of detectable virus. We also demonstrate that priming with live, replicating virus stimulates innate memory more robustly than a highly attenuated vector. These findings shed new light on this emergent area of immunology, and hold significant implications for harnessing innate memory as part of creating novel vaccination strategies.

Role of γδ T Cells in Lung Inflammation

The resident population of γδ T cells in the normal lung is small but during lung inflammation, γδ T cells can increase dramatically. Histological analysis reveals diverse interactions between γδ T cells and other pulmonary leukocytes. Studies in animal models show that γδ T cells play a role in allergic lung inflammation where they can protect normal lung function, that they also are capable of resolving infection-induced pulmonary inflammation, and that they can help preventing pulmonary fibrosis. Lung inflammation threatens vital lung functions. Protection of the lung tissues and their functions during inflammation is the net-effect of opposing influences of specialized subsets of γδ T cells as well as interactions of these cells with other pulmonary leukocytes.

Mismatched antigen prepares gamma delta T cells for suppression of airway hyperresponsiveness

Gammadelta T cells suppress airway hyperresponsiveness (AHR) induced in allergen-challenged mice but it is not clear whether the suppression is allergen specific. The AHR-suppressive cells express TCR-Vgamma4. To test whether the suppressive function must be induced, we adoptively transferred purified Vgamma4(+) cells into gammadelta T cell-deficient and OVA-sensitized and -challenged recipients (B6.TCR-Vgamma4(-/-)/6(-/-)) and measured the effect on AHR. Vgamma4(+) gammadelta T cells isolated from naive donors were not AHR-suppressive, but Vgamma4(+) cells from OVA-stimulated donors suppressed AHR. Suppressive Vgamma4(+) cells could be isolated from lung and spleen. Their induction in the spleen required sensitization and challenge. In the lung, their function was induced by airway challenge alone. Induction of the suppressors was associated with their activation but it did not alter their ability to accumulate in the lung. Vgamma4(+) gammadelta T cells preferentially express Vdelta4 and -5 but their AHR-suppressive function was not dependent on these Vdeltas. Donor sensitization and challenge not only with OVA but also with two unrelated allergens (ragweed and BSA) induced Vgamma4(+) cells capable of suppressing AHR in the OVA-hyperresponsive recipients, but the process of sensitization and challenge alone (adjuvant and saline only) was not sufficient to induce suppressor function, and LPS as a component of the allergen was not essential. We conclude that AHR-suppressive Vgamma4(+) gammadelta T cells require induction. They are induced by allergen stimulation, but AHR suppression by these cells does not require their restimulation with the same allergen.

CD8+ alphabeta T cells can mediate late airway responses and airway eosinophilia in rats

BACKGROUND

The function of CD8+ T-cell subsets in mediating late allergic responses is incompletely understood.

OBJECTIVE

We sought to test the hypothesis that CD8+ alphabeta T cells are proinflammatory in the airways in vivo by using a well-characterized animal model and the technique of adoptive transfer.

METHODS

Brown Norway rats were administered CD8 + alphabeta T cells (10 6 ) intraperitoneally purified from lymph node cells of either naive or ovalbumin (OVA)-sensitized rats and were challenged with aerosolized OVA 2 days later. Control rats were sensitized to 100 mug of OVA in Al(OH) 3 subcutaneously or sham sensitized to saline and were OVA challenged 2 weeks later.

RESULTS

The OVA-sensitized and OVA-challenged group and the recipients of OVA-primed CD8+ alphabeta T cells had significant late airway responses calculated from lung resistance measured for an 8-hour period after challenge compared with the naive CD8 + alphabeta T cell-transferred group and the sham-sensitized control group. The number of eosinophils in bronchoalveolar lavage fluid increased in the OVA-sensitized group and the OVA-primed CD8+ alphabeta T-cell recipients compared with numbers in the naive CD8+ alphabeta T-cell recipients and the sham-sensitized control group. IL-4 and IL-5 cytokine mRNA expression in bronchoalveolar lavage fluid increased in the OVA-sensitized group and the OVA-primed CD8+ alphabeta T-cell recipients compared with that in the sham-sensitized group.

CONCLUSION

We conclude that antigen-primed CD8 + alphabeta T cells might have a proinflammatory role in allergen-driven airway responses in the rat.

Different Potentials of γδ T Cell Subsets in Regulating Airway Responsiveness: Vγ1+ Cells, but Not Vγ4+ Cells, Promote Airway Hyperreactivity, Th2 Cytokines, and Airway Inflammation

Allergic airway inflammation and hyperreactivity are modulated by gammadelta T cells, but different experimental parameters can influence the effects observed. For example, in sensitized C57BL/6 and BALB/c mice, transient depletion of all TCR-delta(+) cells just before airway challenge resulted in airway hyperresponsiveness (AHR), but caused hyporesponsiveness when initiated before i.p. sensitization. Vgamma4(+) gammadelta T cells strongly suppressed AHR; their depletion relieved suppression when initiated before challenge, but not before sensitization, and they suppressed AHR when transferred before challenge into sensitized TCR-Vgamma4(-/-)/6(-/-) mice. In contrast, Vgamma1(+) gammadelta T cells enhanced AHR and airway inflammation. In normal mice (C57BL/6 and BALB/c), enhancement of AHR was abrogated only when these cells were depleted before sensitization, but not before challenge, and with regard to airway inflammation, this effect was limited to C57BL/6 mice. However, Vgamma1(+) gammadelta T cells enhanced AHR when transferred before challenge into sensitized B6.TCR-delta(-/-) mice. In this study Vgamma1(+) cells also increased levels of Th2 cytokines in the airways and, to a lesser extent, lung eosinophil numbers. Thus, Vgamma4(+) cells suppress AHR, and Vgamma1(+) cells enhance AHR and airway inflammation under defined experimental conditions. These findings show how gammadelta T cells can be both inhibitors and enhancers of AHR and airway inflammation, and they provide further support for the hypothesis that TCR expression and function cosegregate in gammadelta T cells.

V gamma 4+ gamma delta T cells regulate airway hyperreactivity to methacholine in ovalbumin-sensitized and challenged mice

The Vgamma4(+) pulmonary subset of gammadelta T cells regulates innate airway responsiveness in the absence of alphabeta T cells. We now have examined the same subset in a model of allergic airway disease, OVA-sensitized and challenged mice that exhibit Th2 responses, pulmonary inflammation, and airway hyperreactivity (AHR). In sensitized mice, Vgamma4(+) cells preferentially increased in number following airway challenge. Depletion of Vgamma4(+) cells before the challenge substantially increased AHR in these mice, but had no effect on airway responsiveness in normal, nonchallenged mice. Depletion of Vgamma1(+) cells had no effect on AHR, and depletion of all TCR-delta(+) cells was no more effective than depletion of Vgamma4(+) cells alone. Adoptively transferred pulmonary lymphocytes containing Vgamma4(+) cells inhibited AHR, but lost this ability when Vgamma4(+) cells were depleted, indicating that these cells actively suppress AHR. Eosinophilic infiltration of the lung and airways, or goblet cell hyperplasia, was not affected by depletion of Vgamma4(+) cells, although cytokine-producing alphabeta T cells in the lung increased. These findings establish Vgamma4(+) gammadelta T cells as negative regulators of AHR and show that their regulatory effect bypasses much of the allergic inflammatory response coincident with AHR.

Both gamma delta T cells and NK cells inhibit the engraftment of xenogeneic rat bone marrow cells and the induction of xenograft tolerance in mice

In murine allogeneic bone marrow transplantation recipients, treatment of the hosts with a nonmyeloablative regimen, including depleting anti-CD4 and anti-CD8 mAbs, allows establishment of long-term mixed chimerism and donor-specific tolerance. However, in the xenogeneic rat-to-mouse combination, additional anti-Thy1.2 and anti-NK1.1 mAbs are required. We have now attempted to identify the xenoresistant mouse cell populations that are targeted by anti-NK1.1 and anti-Thy1.2 mAbs. C57BL/6 (B6) wild-type, B6 TCRbeta(-/-), and B6 TCRdelta(-/-) mice received anti-CD4 and anti-CD8 mAbs, followed by 3 Gy of whole body irradiation, 7 Gy of thymic irradiation, and transplantation of T cell-depleted rat bone marrow cells. Anti-NK1.1 and anti-Thy1.2 mAbs were additionally administered to some groups. Increased rat chimerism was observed in TCRdelta(-/-) mice treated with anti-CD4, anti-CD8, and anti-NK1.1 mAbs compared with similarly treated TCRbeta(-/-) mice. In TCRbeta(-/-) mice, but not in TCR delta(-/-) mice, donor chimerism was increased by treatment with anti-Thy1.2 mAb, indicating that CD4(-)CD8(-)TCRgammadelta(+)Thy1. 2(+)NK1.1(-) cells (gammadelta T cells) are involved in the rejection of rat marrow. In addition, chimerism was enhanced in both TCRbeta(-/-) and TCRdelta(-/-) mice treated with anti-CD4, anti-CD8, and anti-Thy1.2 mAbs by the addition of anti-NK1.1 mAb to the conditioning regimen. Donor-specific skin graft prolongation was enhanced by anti-Thy1.2 and anti-NK1.1 mAbs in TCRdelta(-/-) mice. Therefore, in addition to CD4 and CD8 T cells, gammadelta T cells and NK cells play a role in resisting engraftment of rat marrow and the induction of xenograft tolerance in mice.

Interleukin-15 enhances host protection against acute Toxoplasma gondii infection in T-cell receptor alpha-/-deficient mice

A potential role for T-cell receptor (TCR)-gamma(delta) cells in response to Toxoplasma gondii has been described. This study was undertaken to evaluate whether exogenous rIL-15 can enhance the production of gamma(delta) T cells in response to infection with T. gondii. For this, C57BL/6 and TCR alpha-gene deficient mice (alpha-/-) were vaccinated with Toxoplasma lysate antigen (TLA) in combination with interleukin (IL)-15. The cellular and humoral immune response was assessed following immunization. Administration of IL-15/TLA to alpha-/-mice lengthened survival time post lethal challenge. Several immunological parameters were increased in the alpha-/-mice following immunization with IL-15/TLA including serum immunoglobulin (Ig)G1 and IgG2a antibody titres and splenocyte lymphoproliferation in response to parasite antigen. Further, the CTL response to parasite infected target cells as well as the production of interferon gamma was enhanced by IL-15/TLA administration in the alpha-/-mice. These observations indicate that the gamma(delta) T cells response to this parasite can be enhanced by the administration of exogenous IL-15 in the presence of parasite lysate antigen.

A divalent major histocompatibility complex/IgG1 fusion protein induces antigen-specific T cell activation in vitro and in vivo

Activation of antigen-specific T cell clones in vivo might be possible by generating soluble MHC molecules; however, such molecules do not induce effective T cell responses unless cross-linked. As a first step in generating a soluble MHC molecule that could function as an antigen-specific immunostimulant, the extracellular domains of the murine H-2Kb MHC class I molecule were fused to the constant domains of a murine IgG1 heavy chain, resulting in a divalent molecule with both a TCR-reactive and an Fc receptor (FcR)-reactive moiety. The fusion protein can be loaded with peptide and can induce T cell activation in a peptide-specific, MHC-restricted manner following immobilization on plastic wells or following cross-linking by FcR+ spleen cells. The fusion protein induces partial T cell activation in vivo in a mouse transgenic for a TCR restricted to H-2Kb. This fusion protein molecule may be useful to study peptide-MHC interactions and may provide a strategy for boosting in vivo antigen-specific T cell responses, such as to viral or tumor antigens.

Adenovirus-mediated granulocyte-macrophage colony-stimulating factor improves lung pathology of pulmonary alveolar proteinosis in granulocyte-macrophage colony-stimulating factor-deficient mice

Mutation of the granulocyte-macrophage colony-stimulating factor (GM-CSF) gene by homologous recombination causes progressive pulmonary alveolar proteinosis (PAP) in GM-CSF-deficient mice (GM-/-). The present study tested whether adenovirus-mediated expression of GM-CSF alters the progression of PAP in GM-/- mice. Adult mice were pretreated with an anti-T cell receptor (TCR) antibody to block T cell-mediated immune response, followed by intratracheal instillation of deltaE1-E3 replication-deficient adenovirus expressing mouse GM-CSF (Av1mGM). Mice were killed 1, 3, and 5 weeks after treatment to assess lungs for GM-CSF, surfactant protein B (SP-B), alveolar macrophage maturation, and type II cell proliferation. GM-CSF was detected in BAL fluid from GM-/- mice 1 week after Av1mGM treatment, and GM-CSF mRNA was detected by RT-PCR through 5 weeks. Five weeks after Av1mGM treatment, PAP was improved and SP-B decreased as assessed by ELISA and immunostaining. Increased numbers of alveolar macrophages stained with alpha-naphthyl acetate esterase (alpha-NAE) following treatment with Av1mGM. Local expression of GM-CSF with a recombinant adenovirus ameliorated PAP in the GM-/- mice in association with enhanced maturation of alveolar macrophages.

Anti-T cell receptor antibody prolongs transgene expression and reduces lung inflammation after adenovirus-mediated gene transfer

Replication-deficient delta E1a-E3 adenovirus mediates efficient gene transfer to the mouse lung; however it induces a host immune response mediated, in part, by T cells. This immune response is associated with loss of transgene expression. Monoclonal antibodies (mAb) against the T cell receptor (TCR) complex can inhibit both CD4+ and CD8+ T cell responses in vivo and are the most potent anti-T cell agents in clinical use. To determine whether such mAbs can be used to prolong adenovirus-mediated transgene expression, the vector Av1Luc1 (delta E1a-E3 recombinant adenovirus encoding the firefly luciferase gene) was administered intratracheally to C57BL/6 mice on day 0. Three days prior to adenovirus administration (day -3), mice were treated with a single i.p. injection of the anti-TCR mAb H57. Controls received phosphate-buffered saline. Animals were sacrificed on days 3, 14, 28, and 56 and lungs were assessed for transgene expression and histopathology. Luciferase activity decreased markedly in the controls by day 14, but was maintained at high levels in animals receiving anti-TCR mAb. A mild, focal, predominantly neutrophilic inflammation was observed in the alveoli of all mice 3 days after virus administration. In PBS-treated controls, this inflammation progressed to a moderate to severe multifocal, perivascular and peribronchiolar lymphoid infiltration at 14 days. B cells and T cells were present in approximately equal numbers, with CD4+ T cells predominating over CD8+ T cells by 3- to 28-fold. Treatment with H57 resulted in near-complete prevention of the lymphocytic inflammatory infiltrate and increased luciferase activity throughout the 56-day study period, in association with TCR modulation and T cell depletion. Thus, anti-TCR mAb decreases inflammation and prolongs gene expression following adenovirus-mediated gene transfer.

Alpha/beta- and gamma/delta-T-cell-receptor-positive lymphocytes in healthy and inflamed human conjunctiva

BACKGROUND

The possible existence and distribution patterns of alpha/beta- and gamma/delta-TCR+ cells, which are important constituents of immune surveillance and act via the CD3+ cell complex have not yet been elucidated in the healthy and inflamed conjunctiva.

MATERIALS AND METHODS

Paraffin-embedded conjunctival specimens included 18 from 18 patients with ocular cicatricial pemphigoid (OCP), 20 from 20 healthy controls, 6 from 6 patients with lye burns, and 6 from 2 patients with Stevens-Johnson syndrome; all were worked up by histology and immunohistochemistry.

RESULTS

alpha/beta-TCR+ cells were visualized in the conjunctival epithelium and stroma of healthy persons, OCP, lye burns and Stevens-Johnson syndrome. alpha/ beta-TCR+ cells and a small number of gamma/delta-TCR+ cells were observed in the corneal epithelium and stroma of patients who have failing corneal grafts. After ileal mucosa transplantation to the epibulbar conjunctiva, membrane staining changes to nuclear and cytoplasmic staining. Treatment with systemic cytotoxic drugs abolishes all alpha/beta-TCR+ and gamma/delta-TCR+ cells.

CONCLUSIONS

alpha/beta-TCR+ cells can be found in the non-infected epithelium and stroma of the healthy and inflamed (OCP, lye burns, and Stevens-Johnson syndrome) conjunctiva, as well as in the corneal epithelium and stroma of failing corneal grafts, whereas gamma/delta-TCR+ cells are absent. A small number of gamma/delta-TCR+ cells are present in the corneal stroma and adjacent conjunctival epithelium of patients with chronic corneal graft rejection or after transplantation of gut tissue. Further investigations may establish the role, if any, of these T-cell subsets in immune surveillance of the non-infected outer eye and in corneal graft rejection.

Anti-T cell receptor monoclonal antibody prolongs transgene expression following adenovirus-mediated in vivo gene transfer to mouse synovium

There are no cures for rheumatoid arthritis (RA) or other inflammatory autoimmune arthropathies. Gene transfer to the synovium would allow administration of anti-inflammatory gene products directly to the articular space where they could exert a local down-regulatory effect on the autoimmune process. Several well-characterized murine models of arthritis closely resemble RA immunologically, genetically, and histopathologically. To determine whether the mouse could serve as a model for gene transfer to the synovium, a methodology was developed to reproducibly inject a 5-microliter volume into the articular space of the mouse knee. Using this approach, Av1LacZ4, an E1a-E3-deleted adenoviral (Ad5) vector expressing the lacZ transgene, was delivered intra-articularly (5 x 10(8) pfu). lacZ expression was observed in the articular synovium for at least 14 days. Biochemical quantitation demonstrated a gradual loss of transgene expression, associated with an early, predominantly neutrophilic, inflammatory response that progressed to a lymphocytic infiltrate, followed by gradual resolution over a 3-week period. Pretreatment with the anti-TCR monoclonal antibody (mAb) H57 resulted in a significant reduction in lymphocytic infiltration and a prolongation of transgene expression. These data demonstrate that transgenes can be delivered to the mouse knee joint space, affording a powerful tool to test the potential of gene therapy as a therapeutic modality for RA. As in other systems, the immune response against recombinant adenoviral vectors may limit the extent and duration of gene expression in the synovium. Anti-T cell mAbs may be useful in inhibiting this immune response.

Gamma delta T cells are secondary participants in acute graft-versus-host reactions initiated by CD4+ alpha beta T cells

To examine the role of T cell subpopulations in an acute graft-versus-host (GVH) reaction, gamma delta T cells and alpha beta T cells expressing one of the two prototypic V beta families were negatively isolated from adult blood samples and injected into allogeneic chick embryos. CD4+ alpha beta T cells expressing either V beta 1 or V beta 2 receptors were equally capable of inducing acute GVH reactions, consistent with the idea that alpha beta T cell alloreactivity is determined by CDR3 variability. By themselves, the gamma delta T cells were incapable of inducing GVH reactions. However, host gamma delta T cells were recruited into the donor alpha beta T cell-initiated lesions, where they were activated and induced to proliferate. The data suggest that gamma delta T cells may play a secondary role in GVH reactions.

Immune responsiveness in mutant mice lacking T-cell receptor alpha beta+ cells

Immune responses of mice with T-cell receptor (TCR)gamma delta+ T cells but lacking TCR alpha beta+ cells because of a disruption in the TCR alpha gene, were analysed against alloantigens, soluble protein antigen, killed Mycobacterium tuberculosis and exogenous superantigen. Rejection of skin allografts mismatched for classical major histocompatibility complex (MHC) plus multiple minor H antigens was virtually abrogated but the presence of mismatched Qa-1 non-classical MHC antigens on donor tissue resulted in a significant proportion of TCR alpha-/- mice rejecting such grafts. In view of the proposed role for gamma delta T cells in mycobacterial responses, and particularly against self- or mycobacterial heat-shock protein HSP 65, we examined these responses in TCR alpha-/- mice. Local responses after immunization were low in lymph nodes and no component of these was directed against mycobacterial HSP 65. However, splenic T cells from mutant mice responded strongly to either purified protein derivative (PPD) or M. tuberculosis. Our findings indicate that TCR alpha-/- mice are selectively compromised: while responses to (undefined) mycobacterial antigens were substantial, responses to some other target antigens such as MHC alloantigens and HSP 65, believed to be preferentially recognized by gamma delta receptors, were poor or absent. However, the fact that the mutant mice more readily rejected allografts that are mismatched for the non-classical MHC antigen Qa-1 in addition to classical MHC and minor-H incompatibility, indicates that in some mice the residual immune response, presumed to be by gamma delta cells, is sufficient to cause skin graft rejection and that recognition of non-classical MHC antigens may play an important part in the response.

A monoclonal antibody against T-cell receptor alpha beta induces endogenous cytokines and prevents mice from a lethal infection with Listeria monocytogenes

In vivo induction of cytokines by a monoclonal antibody (mAb) against T-cell receptor (TCR) alpha beta and the protective effect induced by the mAb on a lethal infection with Listeria monocytogenes were studied. Injection of anti-TCR alpha beta mAb induced rapid production of endogenous tumour necrosis factor in the spleens, and gamma interferon and interleukin-6 in the blood streams and spleens of mice. Administration of anti-CD4 mAb, anti-CD8 mAb, or anti-Thy1.2 mAb resulted in suppression of anti-TCR alpha beta mAb-induced endogenous cytokine production. Mice were protected against lethal L. monocytogenes infection when treated with anti-TCR alpha beta mAb. The protective effect was not demonstrated in CD4+ cell- or CD8+ cell-depleted mice. These results suggest that anti-TCR alpha beta mAb shows a protective effect on a lethal infection with L. monocytogenes in mice and that the mAb-induced endogenous cytokines might be involved in the effect of anti-TCR alpha beta mAb.

Changes in the intestinal lymphoid compartment throughout life: implications for the local generation of intestinal T cells

The intestinal lymphoid compartment has a rather stable composition throughout life. However, both during early neonatal development and at high age unique cell populations can be recognized at distinct sites in the intestinal tissue. Directly after birth all intestinal CD3+ cells are found in the lamina propria. At this time the epithelium does not contain T cells. These CD3+ lamina propria lymphocytes co-express both TCR beta and TCR delta chains, probably reflecting the expression of a TCR beta delta heterodimer on the cell surface. Cells with this particular phenotype are present in comparable numbers in the lamina propria of both neonatal euthymic and athymic mice, indicating the thymus-independent nature of these cells. During aging the frequency of TCR alpha beta+ CD8 alpha alpha+ intestinal T cells increases. These cells are also considered to be thymus-independent. The appearance of high numbers of CD4+ CD8 alpha alpha+ intestinal T cells in aged mice is even more striking. It is postulated that the neonatal TCR beta delta+ cells, and probably also the CD4+ CD8 alpha alpha+ cells as found in old mice, are intermediates in the extrathymic differentiation pathway of TCR alpha beta+ CD8 alpha alpha+ intestinal T cells.

Lymphocyte proliferation in mice congenitally deficient in T-cell receptor alpha beta + cells

In mice and humans, T cells are characterized on the basis of T-cell receptor (TcR) expression and divided into the major TcR alpha beta + and minor TcR gamma delta + populations. TcR alpha beta + cells are considered to be the primary regulators of the immune response, whereas the function of TcR gamma delta + cells is unclear. Mice congenitally deficient in TcR alpha beta-expressing cells provide an ideal model for analyzing the independent in vivo function of TcR gamma delta + cells in the absence of TcR alpha beta + cells. Here we report that lymphoid organs in TcR alpha mutant mice undergo substantial enlargement after being challenged by environmental antigens. This organ expansion can be attributed in part to increases in the relative proportions and absolute numbers of TcR gamma delta + cells, but an expansion of the recently described TcR beta + alpha - population also has a role. The expansion of the TcR gamma delta + population is polyclonal, as evidenced by the usage of multiple gamma and delta variable chain segments. Furthermore, a substantial proportion of the cells appears to be activated and these activated cells express surface activation markers. The results clearly demonstrate that TcR gamma delta + cells proliferate independently in response to a broad spectrum of challenges. Moreover, since the expansion of the lymphoid tissues and the TcR gamma delta + cell population is excessive relative to that seen in wild-type animals, one role of TcR alpha beta + cells is directly or indirectly to limit the responses of the other lymphoid components.

Inhibition of skin xenograft rejection by depleting T-cell receptor alpha beta-bearing cells without T-cell receptor gamma delta-bearing cells or natural killer cells by monoclonal antibody

We compared the effects of in vivo administration of the anti-T-cell receptor (TCR) alpha beta monoclonal antibody (mAb) (H57-597) to those of the anti-CD3 mAb (145-2C11), with or without anti-NK1.1 mAb (PK136), on xenogeneic skin graft survival in mice. In anti-TCR alpha beta mAb-treated B6 mice, F344 rat skin grafts survived for about 54 days, whereas in anti-CD3 mAb-treated B6 mice with or without anti-NK1.1 mAb treatment grafts survived about 25 days. In anti-TCR alpha beta mAb-treated B6 mice, TCR alpha beta-bearing T-lymphocyte function was completely abrogated, although TCR gamma delta-bearing T-lymphocyte function was still intact on day 9. In the anti-CD3 mAb-treated mice, the functions of both types of T lymphocytes were completely abrogated. On day 32, when most of the skin xenografts had been rejected in the anti-CD3 mAb-treated mice, the functions of both T lymphocytes had recovered considerably, and could actually respond to F344 antigens. In contrast, the function of TCR alpha beta-bearing cells had only partially recovered in the anti-TCR alpha beta mAb-treated mice. Finally, natural killer (NK) activity in the anti-TCR alpha beta mAb-treated mice was intact on day 32, when rat skin grafts still survived. In contrast, NK activity in the anti-CD3 mAb plus anti-NK1.1 mAb-treated mice did not recover on day 32, when skin xenografts had already been rejected. These results suggest that TCR gamma delta-bearing T cells and NK cells by themselves, at least in the absence of TCR alpha beta-bearing T cells, do not mediate xenogeneic skin graft rejection in mouse/rat combinations.

Inhibition of allograft rejection by anti-T-cell receptor-alpha beta monoclonal antibodies preserving resistance to bacterial infection

Anti-CD3 monoclonal antibody (mAb) has been administered in clinical organ transplantation to reverse acute allograft rejection; however, severe immunodeficiency can result from such mAb treatment and cause an increased incidence of opportunistic infections. Therefore, new model systems are required in order to establish better methods for suppressing allograft rejection while preserving resistance to opportunistic infections. In this study, we compared the effects of the in vivo administration of anti-T-cell receptor-alpha beta (TcR alpha beta) mAb, H57-597, with those of anti-CD3 mAb, 145-2C11. Much to our surprise, the in vivo administration of anti-TcR alpha beta mAb prior to skin grafting led to a longer allograft survival than that of anti-CD3 mAb at any of the comparable dosages examined. In the lymphoid organs of mice treated with anti-TcR alpha beta mAb, TcR alpha beta-bearing cells were almost completely depleted, while TcR gamma delta-bearing cells remained at a relatively increased level on day 14 after anti-TcR alpha beta mAb treatment. The in vitro stimulation by anti-TcR gamma delta mAb clearly showed that such TcR gamma delta-bearing cells were functionally intact. Furthermore, the mice treated with anti-TcR alpha beta mAb, but not anti-CD3 mAb, were observed to be resistant to infection with Listeria monocytogenes. Finally, treatment with H57-597, but not with 145-2C11, led to a marked prolongation of skin allograft survival in the thymectomized mice. These results strongly suggest that anti-TcR alpha beta mAb, which partially preserved anti-bacterial resistance, may be more effective in preventing graft rejection than anti-CD3 mAb in the periphery, and indicate that anti-TcR alpha beta mAb may thus be potentially applicable for human transplantation. In addition, these results also indicate that the TcR gamma delta-bearing cells alone, at least in the absence of TcR alpha beta-bearing cells, do not contribute to allograft rejection in vivo.

In vivo response of murine gamma delta T cells to a heat shock protein-derived peptide

Recent results suggested that a large subset of heat shock protein HSP-60 reactive peripheral lymphoid gamma delta T cells preexists in normal adult mice, all members of which respond to a single segment of this common HSP. However, the experimental evidence supporting this idea involved in vitro peptide responses of gamma delta T-cell hybridomas generated from unprimed spleen cells. Here, we report an attempt to elicit a gamma delta T-cell response in vivo by stimulation of adult C57BL/10 mice with HSP-60 or an HSP-60-derived peptide fragment comprising amino acids 180-196 of mycobacterial HSP-60. Whereas no gamma delta T-cell response was detectable in mice injected with the intact protein, stimulation with the peptide altered the reactive gamma delta T-cell population in vivo. These changes were detected among hybridomas generated with cells restimulated in vitro and included a large increase in hybridizable gamma delta T cells, a nearly maximal increase in the relative frequency of HSP-60-reactive cells, and structural changes in expressed T-cell receptors of HSP-60-reactive cells. Interestingly, we failed to elicit a detectable alpha beta T-cell response to the particular peptide stimulatory for gamma delta T cells, although at least three other HSP-60 epitopes were recognized. Our data show that normal gamma delta T cells can respond in vivo to small peptide antigens. The gamma delta T-cell response to the HSP-60-derived peptide studied here is apparently independent of antigen-specific alpha beta T-cell reactivity.

T cells expressing the gamma delta T-cell receptor potentiate coxsackievirus B3-induced myocarditis

Initial studies determined whether intraperitoneal (i.p.) injection of BALB/c mice with 0.1, 1.0, and 10 mg of adriamycin (a cardiotoxic anthracycline antibiotic) for times ranging between 1 and 9 weeks prior to i.p. injection of 10(5) PFU of coxsackievirus B3 (CVB3) would alter the severity of virus-induced myocarditis. Prior adriamycin exposure enhanced pathogenicity of a poorly pathogenic CVB3 variant (H310A1) but had no effect on myocarditis produced by the pathogenic variant (H3). Cardiac virus concentrations were equivalent in H3- and H310A1-infected mice irrespective of adriamycin treatment. BALB/c mice treated with either 0.1 ml of complete Freund's adjuvant (CFA), 10 mg of adriamycin, or 10(5) PFU of H3 and H310A1 i.p. developed cytolytic Thy 1.2+ lymphocytes (CTL) to H3-infected myocytes 7 days later. CFA-, adriamycin-, and H3-treated mice developed CTL expressing the gamma delta+ T-cell receptors, while H310A1-infected animals did not. Only H3- and H310A1-infected mice developed alpha beta+ CTL. Treatment of BALB/c mice with 0.1 ml of CFA 5 days prior to H310A1 infection dramatically increased myocarditis. Selective depletion of gamma delta+ T cells abrogated this effect. The ability of gamma delta+ T cells to augment the pathogenicity of H310A1 infection was confirmed by adoptive transfer of CFA-stimulated T cells depleted of either gamma delta- or gamma delta+ cells into H310A1-infected recipients.

Lymphoid development in mice congenitally lacking T cell receptor alpha beta-expressing cells

Vertebrate T cells express either an alpha beta or gamma delta T cell receptor (TCR). The developmental relatedness of the two cell types is unresolved. alpha beta + T cells respond to specific pathogens by collaborating with immunoglobulin-producing B cells in distinct lymphoid organs such as the spleen and Peyer's patches. The precise influence of alpha beta + T cells on B cell development is poorly understood. To investigate the developmental effects of alpha beta + T cells on B cells and gamma delta + T cells, mice homozygous for a disrupted TCR alpha gene were generated. The homozygotes showed elimination of alpha beta + T cells and the loss of thymic medullae. Despite this, gamma delta + T cells developed in normal numbers, and there was an increase in splenic B cells.