Both L3T4+ and Lyt-2+ helper T cells initiate cytotoxic T lymphocyte responses against allogenic major histocompatibility antigens but not against trinitrophenyl-modified self

CD4+ T cell help in cancer immunology and immunotherapy

Cancer immunotherapy aims to promote the activity of cytotoxic T lymphocytes (CTLs) within a tumour, assist the priming of tumour-specific CTLs in lymphoid organs and establish efficient and durable antitumour immunity. During priming, help signals are relayed from CD4⁺ T cells to CD8⁺ T cells by specific dendritic cells to optimize the magnitude and quality of the CTL response. In this Review, we highlight the cellular dynamics and membrane receptors that mediate CD4⁺ T cell help and the molecular mechanisms of the enhanced antitumour activity of CTLs. We outline how deficient CD4⁺ T cell help reduces the response of CTLs and how maximizing CD4⁺ T cell help can improve outcomes in cancer immunotherapy strategies.

Role of CD4+ T cells in the rat to mouse cardiac xenotransplantation

T cell subsets involved in rejection of xenografts were analyzed using a rat to mouse cardiac xenotransplant model. Proliferating response and interleulin-2 (IL-2) production in recipients' spleen cells were almost completely abrogated by elimination of L3T4+ T cells, but not by elimination of Lyt2.1+ T cells. Cytotoxic T lymphocyte (CTL) activities were mediated by both L3T4+ and Lyt2.1+ T cells with the help of IL-2-producing L3T4+ T cells. Administration of anti-L3T4 monoclonal antibody (mAb) into recipient mice resulted in a significant prolongation of graft survival (mean graft survival was 29.2 days). Moreover, anti-L3T4 mAb treatment plus thymectomy led to indefinite graft survival. Anti-rat endothelial cell (EC) antibody production in the grafted mice was remarkably suppressed by anti-L3T4 mAb treatment. In contrast, Lyt2.1 mAb treatment did not prolong the graft survival and did not suppress anti-EC antibody production. These results indicated the absolute requirement of L3T4+ T cells in the rejection of rat to mouse cardiac xenografts.

Induction of hyperacute rejection of skin allografts by CD8+ lymphocytes

BACKGROUND

Second-set rejection is generally regarded as a phenomenon mainly mediated by humoral cytotoxic antibodies, although a few discordant data have been presented. In the reported experiments, we have taken advantage of the absence of production of specific cytotoxic alloantibodies contrasting with the normal development of transplantation cellular immunity, in two murine models: chimeric mice and RAG mice.

METHODS

Chimeras (BALB/c-->CBA) were obtained by transplantation of 2x10(7) fetal liver cells from BALB/c (H-2d) mice to lethally irradiated CBA (H-2k) mice. After hyperimmunization with third-party C57/ BL6 (B6) (H-2b) skin transplants and with injections of 2x10(7) B6 spleen cells, antibody production, and skin graft survival were analyzed. To identify further the factors or cells responsible for accelerated rejection of B6 skin transplants in hyperimmunized chimeras, transfer experiments were carried out involving the injection of serum, whole spleen cells, spleen T cells, spleen CD8+ T cells or spleen CD4+ T cells from chimeras into BALB/c mice that had received 6 Gy irradiation. The recipient mice were then grafted with B6 skin. Similarly, the immunodeficient RAG mice were used to construct a model of recipient animals with anti-H-2d hyperimmunized B6 T cells in the total absence of antibody.

RESULTS

In chimeras, anti-B6 cytotoxic antibodies were not detectable in any of hyperimmunized chimeric mice, yet accelerated rejection of B6 skin transplant occurred: a graft survival of 8.6+/-0.5 days (d), comparable to 8.9+/-0.8 d survival in CBA control mice subjected to the same hyperimmunization procedure, and significantly shorter than that in nonhyperimmunized (BALB/c-->CBA) chimeras (11.6+/-0.5 d) or in non-hyperimmunized CBA control mice (12.1+/-0.6 d). High titers of anti-B6 cytotoxic antibodies were present in the serum of hyperimmunized CBA control mice. In transfer experiments, the graft survival was over 14 d in mice treated with irradiation alone, with irradiation + serum or with irradiation + CD4+ T cells. It was significantly shorter in mice treated with irradiation + whole spleen cells, with irradiation + T cells or with irradiation + CD8+ T cells (8.9+/-0.8 d). Similarly, in immunodeficient RAG mice, reconstitution of the T cell compartment with T cells from hyperimmunized B6 mice led to accelerated rejection of BALB/c skin allografts (11.4+/-1.1 d vs. 18.8+/-0.8 d when T cells were provided by nonimmunized mice). In a second transfer of cells from these reconstituted RAG mice into naive RAG mice, CD8+ T cells were shown to induce accelerated rejection of skin allografts (12.0+/-0.6 d) whereas CD4+ T cells were much less efficient (16.5+/-0.1 d).

CONCLUSION

These data indicate that T cells, and especially the CD8+ subset, can be responsible for second-set rejection in the absence of anti-donor antibodies in chimeric and RAG mouse models. These sensitized CD8+ T cells are also likely to play an important role in normal mice, in addition to that of cytotoxic antibodies.

Involvement of CD4(+) Th1 cells in systemic immunity protective against primary and secondary challenges with Trypanosoma cruzi

In general, gamma interferon (IFN-gamma)-producing CD4(+) Th1 cells are important for the immunological control of intracellular pathogens. We previously demonstrated an association between parasite-specific induction of IFN-gamma responses and resistance to the intracellular protozoan Trypanosoma cruzi. To investigate a potential causal relationship between Th1 responses and T. cruzi resistance, we studied the ability of Th1 cells to protect susceptible BALB/c mice against virulent parasite challenges. We developed immunization protocols capable of inducing polarized Th1 and Th2 responses in vivo. Induction of parasite-specific Th1 responses, but not Th2 responses, protected BALB/c mice against virulent T. cruzi challenges. We generated T. cruzi-specific CD4(+) Th1 and Th2 cell lines from BALB/c mice that were activated by infected macrophages to produce their corresponding cytokine response profiles. Th1 cells, but not Th2 cells, induced nitric oxide production and inhibited intracellular parasite replication in T. cruzi-infected macrophages. Despite the ability to inhibit parasite replication in vitro, Th1 cells alone could not adoptively transfer protection against T. cruzi to SCID mice. In addition, despite the fact that the adoptive transfer of CD4(+) T lymphocytes was shown to be necessary for the development of immunity protective against primary T. cruzi infection in our SCID mouse model, protective secondary effector functions could be transferred to SCID mice from memory-immune BALB/c mice in the absence of CD4(+) T lymphocytes. These results indicate that, although CD4(+) Th1 cells can directly inhibit intracellular parasite replication, a more important role for these cells in T. cruzi systemic immunity may be to provide helper activity for the development of other effector functions protective in vivo.

Specific inhibition of CD4+ T lymphocytes by a hybrid antibody

T lymphocytes are crucial in the defense against foreign intruders and cancerous growths. Yet, in circumstances such as transplantation or autoimmunity, T-cell-mediated responses can be detrimental. Inhibition of these deleterious responses is currently achieved by drugs that induce general immune suppression. These compounds also impair the patient's defenses against infections. Strategies are now being sought that induce selective rather than generalized immune unresponsiveness. One such strategy is the ability to inhibit the activation of CD8+ T lymphocytes. As CD4+ T lymphocytes similarly participate in graft rejection and in autoimmune diseases, we have now developed a reagent to delete their activity. It comprises CD4 and an anti-MHC class II antibody. By virtue of the antibody's specificity for MHC class II molecules, this hybrid antibody (Hab) binds to class II molecules, thereby bringing CD4 accessory molecules to the surface of class II-bearing stimulator cells where they occupy CD4 binding sites on class II molecules. As a consequence CD4+ T cells with specificity to Hab-coated stimulator cells cannot engage their CD4 molecules and are no longer activated. This Hab technology provides a strategy to offer specific rather than generalized immune suppression.

Immunological characteristics of the effector cells induced by a combination therapy with cyclophosphamide and allogeneic lymphocytes

A significant inhibition of tumor growth was observed when sarcoma 180 (S180)-bearing ICR strain mice were treated by a combination therapy, with a low dose of cyclophosphamide (CY) and an inoculation of allogeneic lymphocytes collected from C57BL/6 mice. The growth-inhibitory effect was significantly increased by an inoculation of a relatively lower dose of allogeneic lymphocytes (1 x 10(5) cells) and CY. The effector cells induced in the mice treated with CY and allogeneic lymphocytes expressed the Lyt 1.2, Lyt 2.2, IL-2R antigens on their membrane surface and did not express the H2KbDb (donor H-2) antigen, and they showed a specific cytostatic activity against S180 cells. These results strongly suggested that a combination therapy with a low dose of CY with an inoculation of allogeneic lymphocytes augmented an induction of specific cytotoxic T lymphocytes in the tumor-bearing recipient mice.

Induction of autoimmune-like hepatic and ductal lesions by administration of lipopolysaccharide in mice undergoing graft-versus-host reaction across MHC class I difference

In this paper, we examined the induction of autoimmune-like histologic changes in the liver and other organs of mice undergoing graft-versus-host reaction (GVHR) with MHC class I disparity by the administration of bacterial lipopolysaccharide (LPS), on the assumption that stimulation with LPS could be an exacerbating factor. Spleen cells of C57BL/6 (B6) mice were injected twice into (B6 x bml) F1 recipient mice at an interval of 7 days to induce MHC class I GVHR and then challenged with 1 microg of LPS intravenously on the next day of the cell transfer. The hepatic lesions of the group of MHC class I GVHR mice challenged with LPS showed marked cellular infiltration at the portal area and focal necrosis was observed in the hepatic lobule. The major infiltrating cells were CD8+, and others including CD4+ cells being of minor populations. In addition, ductal lesions in extrahepatic organs, including the pancreas and salivary glands also showed marked cellular infiltration. Thus, we have demonstrated that LPS induced ductal lesions in mice with MHC class I disparity. CD8+ cells were detected at the destructive hepatic lesions, which might be effector cells. These findings indicate that LPS might be one of the potential factors which augment autoimmune-like lesions.

Analysis of T-cell responses in cattle immunized against heartwater by vaccination with killed elementary bodies of Cowdria ruminantium

Cattle were successfully immunized against heartwater with a lysate of Cowdria ruminantium formulated in Freund's adjuvant. Vaccinated animals proved fully resistant to virulent challenge 3 and 10 months after vaccination. For the first time a helper T lymphocyte response to Cowdria antigens was observed and characterized. Cowdria-specific T-cell lines generated from vaccinated animals by in vitro restimulation with Cowdria lysates are 95 to 100% CD4+, are MHC class II restricted, and produce gamma interferon. They proliferate in response to autologous monocytes infected with live Cowdria but not in response to uninfected monocytes. These T-cell lines will facilitate the search for Cowdria antigens that are immunogenic for T cells and will therefore be of relevance in the development of a subunit vaccine against the disease.

MHC class I presentation of an exogenous polypeptide antigen encoded by the murine AIDS defective virus

Peptides derived from endogenous proteins are presented by MHC class I molecules, whereas those derived from exogenous proteins are presented by MHC class II molecules. This strict segregation has been reconsidered in recent reports in which exogenous antigens are shown to be presented by MHC class I molecules in the phagocytic pathway. In this report, the presentation pathway of an exogenously added highly antigenic polypeptide encoded by the murine AIDS (MAIDS) defective virus gag p12 gene is investigated. A 25-mer polypeptide (P12-25) encoded within the gag p12 region of the MAIDS defective virus was found to be effective in stimulating unprimed B6 (H-2b) CD8+ T cells in vitro. The presentation of P12-25 is sensitive to cytochalasin B and D, brefeldin A and gelonin, a ribosome-inactivating protein synthesis inhibitor, but less sensitive or resistant to lactacystin, a highly specific inhibitor of the proteasome. Interestingly, CA-074, a selective inhibitor of cathepsin B, inhibited presentation of the polypeptide, indicating its involvement in the degradation of the P12-25 polypeptide. In fact, when P12-25 was digested with purified cathepsin B in vitro, a highly antigenic 11-mer peptide containing the class I (H-2Db)-binding motif was obtained. Our results favor the phagosome/macropinosome-to-cytosol-to-endoplasmic reticulum (ER)-to-cell surface pathway for exogenous antigens presented by MHC class I molecules. These findings may be relevant to exploiting peptide vaccines that specifically elicit CD8+ T cell immunity in vivo.

Effect of major histocompatibility complex matching on the development of tolerance to primarily vascularized renal allografts: a study in miniature swine

Prevention of rejection and the induction of transplantation tolerance are two related but separable phenomena that must both be considered in the analysis of the response to a transplanted organ. It is frequently hard to separate these phenomena in assessing the outcome of clinical transplants, because patients are rarely studied in the absence of immunosuppressive agents. Use of our partially inbred miniature swine has permitted us to examine the effects of selective MHC matching on transplant survival, and the data indicate that matching has an effect on both phenomena. Prevention of early rejection with CyA was possible for all mismatches examined, although it was clearly more difficult with increasing degrees of mismatching. On the other hand, tolerance induction after cessation of the immunosuppressive agent was dependent on presence of at least one matched MHC locus between the donor and recipient, with complete class II matching appearing to be the most successful way of assuring long-term graft survival. It is also apparent from our data that although durable tolerance to primarily vascularized renal allografts could be induced across a variety of selective MHC disparities, all cases involving a class II mismatch (ie, selective class I matched or one-haplotype full MHC mismatched kidney allografts) underwent spontaneously reversible rejection crises during the early follow-up period. Such a clinical course might be unacceptable for human clinical trials, even though the transient renal dysfunction may reflect events involved in tolerance induction rather than true rejection (Gianello et al: Immunol Rev 133:19, 1993.). Indeed, we do not yet know whether or not further immunosuppressive treatment at the times of such crises may prevent rather than facilitate the induction of tolerance. On the other hand, in the case of selective two-haplotype class I mismatch the regimen utilized was capable of inducing tolerance to renal allografts in 100% of the recipients with minimal or no renal dysfunction throughout the follow-up period. Although the excellent results achieved with current antirejection agents has led to debate about the wisdom of HLA matching for cadaver transplants in terms of preventing rejection, our data would suggest that such matching might be of even greater importance for success of protocols in which attempts are made to induce transplantation tolerance. Because class II antigens are less polymorphic than are class I antigens, mismatching for class I antigens may be achievable for cadaver donor transplantation, and may provide the first situation in which these principles can be applied to clinical trials.

Morphine inhibits the development of allogeneic immune responses in mouse lymph node

Morphine and related opiates are often administered to relieve post-operative and chronic pain following transplantation surgery. Opiates have been shown to suppress a variety of immune parameters in both animal models and man. In the present study, we investigated whether morphine affects allogeneic immune responses by injecting C57BL/6 mice in the footpad with allogeneic spleen cells and examining changes in the draining popliteal lymph node (PLN). Morphine (administered as subcutaneous implants) had profound inhibitory effects on the development of alloreactivity manifested as a suppression of: (1) lymph node hyperplasia, (2) mixed lymphocyte reactivity (MLR) in PLN cells and (3) the number of CD4+ and Thy 1.2 lymphoid subsets. These inhibitory effects of morphine were abolished or dramatically reduced by co-administration of the opiate antagonist, naltrexone, indicating that suppression of allo-sensitization was opiate receptor mediated. In toto, these findings demonstrate that morphine administration interferes with the development of allogeneic immune response in mouse lymph node through an opiate receptor mediated mechanism.

Concentric fibrosis and cellular infiltration around bile ducts induced by graft-versus-host reaction in mice: a role of CD8+ cells

We report in this paper on obvious fibrotic lesions in the liver of mice undergoing specified graft-versus-host reaction (GVHR). B6 CD8+ splenocytes were transferred into (bm 12 x bm 1)F1 mice to induce GVHR. Recipient mice had been thymectomized and administrated with anti-CD8 monoclonal antibody (mAb) to deplete CD8+ cells from the hosts. Two weeks after the mAb administration, recipient mice were injected with B6 CD8+ cells and sacrificed further two or four weeks later for analyzing hepatic lesions histopathologically. Light microscopic analyses revealed the presence of concentric fibrosis around both small and large duct levels and the infiltration of mononuclear cells into portal areas. Focal necrosis of hepatocytes was also detected electron-microscopically. These findings suggest that CD8+ T lymphocytes might play an important role in the induction of fibrotic lesions in the liver.

L3T4+ but not LYT2+ T-helper cells are required for in vitro maturation of in vivo primed T cells in the cytotoxic response to MHC class I disparate cells following footpad immunization

The induction characteristics of major histocompatibility complex (MHC) class I-specific cytotoxic T lymphocytes (CTL) after footpad immunization were studied. Primary CTL were generated in the regional lymph nodes of C57Bl/6 mice by footpad injection with 10(7) irradiated (2000 rad) spleen cells from MHC class I mutant mouse strain (bm1) followed by a short in vitro culturing without antigen. The requirement of accessory cells and L3T4+ T cells during in vitro maturation of in vivo primed CTL precursor (CTLp) was shown. Moreover, using inhibitory antibodies, the need for IL-2 and IL-4 for in vitro maturation of CTL was established. We have suggested that accessory cells act at the level of L3T4+ T cells which in turn non-specifically up-regulate the CTL response through the production of growth and differentiation factors. Thus, the T-helper population of L3T4+ but not Lyt2+ phenotype appears to be recruited in the in vitro maturation of in vivo primed CTLp in a given system. Possible mechanisms of this phenomenon are discussed.

The cytotoxicity of macrocyclic trichothecenes, roridin A and verrucarin A, on murine T-cells is reduced by Ia-negative splenic adherent cells

The in vitro effect of macrocyclic trichothecenes, roridin A and verrucarin A, and a non-macrocyclic trichothecene, T-2 toxin, on the concanavalin A-induced murine T-cell blastogenesis was investigated. The macrocyclic trichothecenes inhibited the blastogenesis of both thymocytes and splenocytes, splenocytes being more resistant than thymocytes. Such resistance to macrocyclic trichothecenes was not observed in splenic T-cells separated from the other cell population, nor in splenocytes depleted of adherent cells. In order to find the cell population responsible for resistance, the toxins were incubated with fractionated splenic cells and then cytotoxicity of the supernatants of the incubation mixtures was examined by using T-cell blastogenesis assay. The results showed that the splenocytes depleted of Ia-negative cells had the ability to reduce the cytotoxicity of the macrocyclic trichothecenes, but not that of T-2.

Evaluation of functional heterogeneity in the CD8 subset with T cells from T cell receptor-transgenic mice

The question of functional differentiation within the CD8 subset has been addressed in a model of TcR-transgenic (TcR-tg) mice expressing a TcR specific for H-2Kb (Ti). CD8+ Ti+ T cells present in the periphery of these mice have no cytotoxic T lymphocyte (CTL) activity unless they are stimulated with H-2Kb-expressing cells. In contrast to T cells from normal H-2k littermates, alloantigen induction of CTL from TcR-tg mice is independent of CD4+ T helper (Th) cells and is accompanied by high level secretion of interleukin-(IL)-2 by Ti+ CD8+ T cells. Precursor frequency analysis performed on CD8+ cells from TcR-tg mice revealed a high frequency of Th as compared to CTL precursors. This raised the possibility of the existence of distinct subpopulations within CD8+ precursors with different requirements for differentiation to functional CTL. FACS analyses (performed on resting and on in vitro stimulated T cells from normal and TcR-tg mice) demonstrated a heterogeneous expression of Ly-6C on CD8+ cells with a large enrichment of Ly-6C- cells among the Ti+ cells which persisted after stimulation with H-2b cells in conditions that led to a homogeneous expression of the activation markers pgp-1 and CD69. The possibility that Ly-6C expression could mark functionally different subpopulations in CD8+ T cells was investigated. Stimulation of sorted populations of Ly-6C- and Ly-6C+ cells allowed detection of CTL precursors in both these subsets and the majority of limiting dilution wells containing one pCTL also scored positive for IL-2 secretion. Thus, for CD8+ T cells expressing the same TcR, differentiation led to acquisition of both IL-2 secretion and CTL function and there was no evidence for the existence of a distinct population of helper-dependent CTL precursors.

Autoimmune diabetes can be induced in transgenic major histocompatibility complex class II-deficient mice

Insulin-dependent diabetes mellitus (IDDM) is an autoimmune disease marked by hyperglycemia and mononuclear cell infiltration of insulin-producing beta islet cells. Predisposition to IDDM in humans has been linked to the class II major histocompatibility complex (MHC), and islet cells often become aberrantly class II positive during the course of the disease. We have used two recently described transgenic lines to investigate the role of class II molecules and CD4+ T cells in the onset of autoimmune insulitis. Mice that are class II deficient secondary to a targeted disruption of the A beta b gene were bred to mice carrying a transgene for the lymphocytic choriomenigitis virus (LCMV) glycoprotein (GP) targeted to the endocrine pancreas. Our results indicate that class II-deficient animals with and without the GP transgene produce a normal cytotoxic T lymphocyte response to whole LCMV. After infection with LCMV, GP-transgenic class II-deficient animals develop hyperglycemia as rapidly as their class II-positive littermates. Histologic examination of tissue sections from GP-transgenic class II-deficient animals reveals lymphocytic infiltrates of the pancreatic islets that are distinguishable from those of their class II-positive littermates only by the absence of infiltrating CD4+ T cells. These results suggest that in this model of autoimmune diabetes, CD4+ T cells and MHC class II molecules are not required for the development of disease.

Transplantability and MHC antigen expression of tumor mast cells

A cloned cell line was established from tumor cells spontaneously developed in a coculture of an autoreactive T cell line (1/+ T1) and 30 Gy-irradiated MRL/+ spleen cells with Con A supernatants. Morphological studies and studies of histamine content and modes of histamine release after stimulation with compound 48/80 revealed that the cell line (MRL-MC3) had mast cell characteristics. MRL-MC3 was transplantable not only to MRL/+, MRL/lpr and AKR/J (H-2k) mice but also to BALB/c and (BALB/c x DBA/2) F1 (H-2d) mice, although the allogeneic mice survived twice as long as syngeneic mice after i.v. injection. In addition, after i.v. injection, the mast cells infiltrated the livers and spleens of syngeneic (MRL/+) mice, however the lymph nodes around the mesenterium to the parapylorus in allogeneic (BALB/c) mice. A mast cell line (BALB-MC) was also established from a lymph node of MRL-MC3-injected BALB/c mice. Cell surface marker analyses revealed clear differences between the BALB-MC and the original MRL-MC3, which was positive for the expression of MHC class I antigens (K, D), I-E antigen and c-abl-encoded (anti-pEX-2 antibody-reactive) proteins, but not for I-A on the cell surface. In contrast, BALB-MC showed positive only for the MHC class I antigens (K, D) on the surface, and also positive for anti-pEX-2 antibody-reactive cytoplasmic proteins, as seen in MRL-MC3. Mast cells obtained from MRL-MC3-injected MRL/+ mice showed the same staining pattern as MRL-MC3. BALB-MC induced shorter survival times (approximately half) in both MRL/+ and BALB/c mice than MRL-MC3.(ABSTRACT TRUNCATED AT 250 WORDS)

Rat pancreatic islet pretreatment with anti-MHC class II monoclonal antibodies and culture: in vitro MLIC test response does not predict islet allograft survival

Antigen presenting cells (APC) expressing MHC class II antigens have been attributed with stimulatory capacity for initiating islet allograft rejection (direct pathway). Therefore, we evaluated the effect of pretreating isolated islets with different monoclonal antibodies against MHC class II antigens and complement, with and without culture at 22 degrees C or 37 degrees C, on MHC class II antigen expression, on the allogeneic proliferative response in the mixed lymphocyte islet culture (MLIC) and on islet allograft survival in adult rats. Experiments were performed in two different strain combinations incompatible for MHC class II antigens and either incompatible or compatible for MHC class I antigens, in order to elucidate further the impact of class I antigens on islet allograft rejection. In terms of class II antigen suppression, pretreatment with anti-MHC class II antibodies together with complement and a 5-day (37 degrees C) culture period proved most effective. After this procedure 92.7% of the islets of LEW rats and 91.1% of the islets of LEW.1WR2 rats were negative for MHC class II antigens, as demonstrated by indirect immunofluorescence. Transfer of successfully pretreated islets to a MLIC in vitro test system provoked a significantly reduced allogeneic T-cell proliferative response in the case of additional MHC class I disparity (ratio 1.3 vs 4.7) and a response as low as that of a syngeneic setting when stimulator islets and allogeneic responder lymphocytes shared MHC class I antigens (ratio 1.0 vs 1.6).(ABSTRACT TRUNCATED AT 250 WORDS)

Helper interleukins are produced by both CD4 and CD8 splenic T cells after mitogen stimulation

We have earlier described (Cardell, S. and Sander, B., Eur. J. Immunol. 1990. 20:389) mitogen-induced production of interleukin (IL)2, IL4 and IL5 mRNA by murine spleen cells, analyzed by in situ hybridization. In the present study we have investigated the potential of CD8 T cells to produce these interleukins, normally associated with the helper function of CD4 T cells. When concanavalin A (Con A)-activated spleen cells were restimulated with Con A and phorbol 12-myristate 13-acetate (PMA), higher levels of IL2, IL4 and IL5 mRNA were induced, as detected both by increased frequencies of positive cells, and by more mRNA per cell. Four-to-six-day Con A blasts were enriched for CD4+ or CD8+ T cells, and restimulated with Con A and PMA. Both CD4 and CD8 cells were found to produce all three kinds of mRNA when restimulated. The frequencies of IL2 mRNA-containing CD8 cells were half of those found for CD4 cells (3.5% as compared to 7%). On the average 1% of the CD8 cells were induced to produce IL4 and IL5 mRNA, while 9% and 3% of the activated CD4 cells contained IL4 and IL5 mRNA, respectively. CD4 and CD8 cells displayed different sensitivities to the reagents when tested alone. Con A induced the synthesis of IL4 and IL5 in CD4 cells, but not CD8 cells, independently of PMA. PMA alone induced extensive thymidine incorporation in CD8 cells, but not in CD4 cells, in the absence of detectable lymphokine mRNA. The results suggest that some CD8 cells have the capacity to give help in immune responses, by secretion of IL2, IL4 and IL5.

Cytotoxic T lymphocyte precursor cells specific for the major histocompatibility complex class I-like antigen, Qa-2, require CD4+ T cells to become primed in vivo and to differentiate into effector cells in vitro

Experiments were performed to determine whether CD4+ T cells are required for the generation of cytotoxic T lymphocytes (CTL) specific for the nonpolymorphic major histocompatibility complex (MHC) class I-like antigen, Qa-2. Splenic T cells from BALB/cBy (Qa-2b) mice that had been immunized with irradiated BALB/cJ (Qa-2a) splenocytes generated CTL following in vitro stimulation with BALB/cJ splenocytes. These CTL lysed all Qa-2+, but not Qa-2- targets, regardless of the H-2 haplotypes of target cells or their non-MHC backgrounds. This apparent MHC class I-unrestricted recognition of Qa-2 antigen was confirmed using Qa-2-specific CTL clones. The Qa-2-primed CTL precursor cells (CTLp) and CTL were found to be CD8+ T cells. Primed splenocytes depleted of CD4+ T cells prior to culture failed to generate CTL, but addition of lymphokines to the culture restored the CTL generation. Stimulation of primed splenic T cells with irradiated Qa-2+ T blast cells, instead of splenocytes or B blast cells, led to little to no CTL generation, suggesting that MHC class II molecules are involved in the presentation of Qa-2 antigen to CD4+ T cells. This was also supported by the results of experiments using Qa-2+, class II- thymoma cells of BALB/c origin. Stimulation of the thymoma-primed splenic T cells with the mitomycin C-treated thymoma cells resulted in no generation of anti-Qa-2 CTL, despite the fact that high levels of CTL specific for minor histocompatibility (H) antigens and H-2d were generated by immunizing the corresponding allogeneic hosts with the thymoma. However, the addition of lymphokines rendered thymoma-primed T cells capable of generating anti-Qa-2 CTL. Both CD4+ and CD8+ T cell populations, isolated from the BALB/cJ splenocyte-primed responder cells, proliferated in vitro in response to the Qa-2+ splenocytes, suggesting that Qa-2-reactive CD4+ T cells were present in the immunized mice. Depletion of CD4+ T cells from thymectomized BALB/cBy mice with anti-L3T4 monoclonal antibodies markedly reduced, but did not eliminate anti-Qa-2 CTL generation. In contrast, depletion of CD8+ T cells led to a complete abrogation of the CTL response. Addition of lymphokines to the culture of responder cells depleted of either T cell subset did not restore their reactivity. It is concluded that anti-Qa-2 CTLp need "help" from CD4+ T cells to become primed in vivo. Furthermore, primed CTLp also need "help" or lymphokines provided by CD4+ T cells to differentiate into effector CTL in vitro.(ABSTRACT TRUNCATED AT 400 WORDS)

Identification of unique murine tumor associated antigens by tumor infiltrating lymphocytes using tumor specific secretion of interferon-gamma and tumor necrosis factor

Stimulation of multiple CD8+ murine tumor infiltrating lymphocyte (TIL) lines and one TIL clone with the tumor of origin of the TIL induced at least three-fold more secretion of TNF and/or INF-gamma than was elicited by other syngeneic, methylcholanthrene (MCA) induced sarcomas. TIL which specifically secreted lymphokines were generated from three different sarcomas. Specific lymphokine secretion was a stable characteristic of the lines over time. IL-2 was necessary for maximal lymphokine secretion by TIL. These investigations demonstrate that lymphokine secretion by CD8+ lymphocytes derived from tumor bearing mice can be used to define unique tumor associated antigens on at least three different sarcomas and may be valuable in studies of the biologic nature of these antigens and of the adoptive immunotherapy of cancer.

CD3+ T cells in severe combined immunodeficiency (scid) mice. II. Transplantation of dm2 lymphoid cells into semi-allogeneic scid mice

Intravenous injection of nonfractionated BALB/c-H-2dm2 (dm2) (Ld-) spleen cells into 4-week-old, semi-allogeneic (H-2d, Ld+) C.B-17 scid/scid severe combined immunodeficient (scid) mice (2 x 10(7) cells/mouse) reconstituted T lymphopoiesis in thymi and repopulated the lymphoid white pulp in spleens of these immunodeficient recipients. Transplantation of dm2 thymocytes into young scid mice (5 x 10(7) cells/mouse) established a donor-derived CD3+ T cell population in spleens of recipient scid mice, in which CD4+T cells predominated. This was demonstrated by marker analyses of thymocytes and splenocytes, and determinations of serum immunoglobulin levels in transplanted scid mice. Transfer of splenocytes from young primary scid recipients into young secondary or tertiary recipients (3 x 10(6) cells/mouse) engrafted preferentially dm2-derived CD3+CD4+CD8- T cells in spleens of scid mice despite the strong selective Ld-associated alloantigenic stimulus for CD8+ T cells. Intravenous injections of nonfractionated dm2 spleen cells (2 x 10(7) cells/mouse) or thymocytes 5 x 10(7) cells/mouse) into 10- to 12-month-old, "leaky" scid mice induced severe clinical signs of graft-vs.-host disease (GVHD) in all scid recipients. Lymphoid repopulation of spleen and thymus in old scid recipients was incomplete. This GVHD was not transferrable by injecting 3 x 10(6) spleen cells from old diseased primary scid recipients into secondary or tertiary young scid recipient mice. In these serial transfers, dm2-derived CD3+CD4+CD8- T cells were again preferentially engrafted in spleens of scid recipients. Transfer of purified CD4+ dm2 T cells into young scid mice (2 x 10(5) to 5 x 10(5) cells/mouse) engrafted this T cell subset into the spleen of semi-allogeneic scid recipients. This was revealed by histological examinations, surface marker analyses, in vitro isolation of donor-type CD3+CD4+ T cell lines from spleens of transplanted scid mice, and serial transfer experiments. These data indicated that the CD4+ T cell compartment of scid mice can be selectively repopulated by semi-allogeneic T cells. Injections of purified CD8+ dm2 T-cells into young scid mice (2 x 10(5) cells/mouse) did not establish a CD8+ T cell graft in spleens of recipients. It was necessary to inject transplanted scid mice biweekly with 10(4) units recombinant interleukin 2 to establish and/or maintain transferred dm2 CD8+ T cells in spleens of these recipients, dm2 CD8+ T cell-transplanted and interleukin 2-treated scid mice did not develop any evidence of GVHD over the 9-week observation period.

T helper cells in cytotoxic T lymphocyte development: analysis of the cellular basis for deficient T helper cell function in the L3T4-independent T helper cell pathway

In this present study, lymphokine (IL-2/IL-4) production in VSV-induced Th cell (L3T4+Lyt-2- VSV-immune T cells) and memory CTL populations (L3T4-Lyt-2+ VSV-immune T cells) has been assessed in order to gain some understanding as to why the Lyt-2+ subset (L3T4-independent Th cell pathway) fails to provide Th cell function for anti-VSV CTL responses. Our studies demonstrated that following specific antigen (VSV, H-2 antigen) or mitogen stimulation, lymphokine activity was detected in the supernatants obtained from VSV-induced Th but not VSV memory CTL populations. The presence of blocking concentrations of PC61, a monoclonal antibody (mAb) to the IL-2 receptor (IL-2R), revealed augmented lymphokine activity only in the VSV-induced Th cell supernatant. VSV-induced Th cells secreted both IL-2 and IL-4 following stimulation with VSV. Two lines of evidence supported the view that both these lymphokines were important for an anti-VSV CTL response: (1) mAb to either IL-2 or IL-4 inhibited CTL maturation and (2) the combination of exogenous IL-2 and IL-4 reconstituted a class I-restricted. VSV-specific CTL response in Th cell-depleted T cell cultures. The failure to detect lymphokine production in bulk cultures of the VSV memory CTL population was consistent with limiting dilution (LD) analysis of lymphokine-producing cells in the spleen of VSV-immune mice. Thus, approximately 1/15,000 Lyt-2-depleted, VSV-immune T cells were positive for lymphokine production following VSV stimulation, whereas less than 1/1,000,000 L3T4-depleted, VSV-immune T cells were scored as lymphokine-secreting cells following stimulation with this same virus. Similarly, precursor estimates for lymphokine-producing cells against allogeneic class I antigens demonstrated that the majority of lymphokine-producing cells also resided in the L3T4+ subset. Lymphokine-secreting Lyt-2+ cells were detected at low but not high cell densities suggesting that Lyt-2+ cells may secrete another lymphokine(s) that inhibits IL-2/IL-4 production. Thus, these studies demonstrate an obligatory requirement for the L3T4-dependent Th cell pathway for optimal CTL responses derived from either CTLp or memory CTLs.

CD4-positive T lymphocytes are required for the generation of the primary but not the secondary CD8-positive cytolytic T lymphocyte response to herpes simplex virus in C57BL/6 mice

To understand the cellular basis for recovery from HSV infection, it is critical to identify functional interactions between HSV-specific T lymphocyte subpopulations involved in the generation of the optimal response. To this end, the requirement for CD4+ (L3T4+) T lymphocytes in the development of the primary and secondary CD8+ (Lyt-2+) cytolytic T lymphocyte (CTL) response following HSV infection in C57BL/6 mice was investigated. It was found that chronic depletion of CD4+ cells in vivo by treatment with the mAb GK1.5, which resulted in greater than 95% depletion of peripheral CD4+ T lymphocytes in treated animals, caused a profound decrease in the levels of cytolytic activity obtained during the primary response in the draining popliteal lymph nodes of mice responding to infection in the hind footpads. However, treatment did not affect the levels of in vivo secondary CTL activity in the popliteal lymph nodes, nor the in vitro secondary response in the spleen. The decreased CTL activity observed during the primary response was not due to an inability to prime HSV-specific CTL precursors (CTLp), as full cytolytic activity was obtained following culture of lymphocytes in the presence of exogenous IL-2 and antigen, and the response could be reconstituted by treatment with recombinant IL-2 in vivo. Analysis of the secondary CTL response in the spleen indicated that CD4+ cells were not required for either the generation or maintenance of this aspect of the response. However, blockade of IL-2 utilization by CTL using anti-IL-2R antibodies indicated that this lymphokine was absolutely essential for secondary CTL expansion in vitro. Finally, mice that had been infected 12 months previously exhibited a decreased ability to generate secondary HSV-specific CTL in vitro following CD4-depletion in vivo. Taken together, these results suggest two distinct stages of CTL development during the response: an early primary stage dependent upon the presence of CD4+ cells, and a later, CD4-independent stage operative during the secondary response, which decays with time postinfection.

T helper cells in cytotoxic T lymphocyte development: role of L3T4(+)-dependent and -independent T helper cell pathways in virus-specific and alloreactive cytotoxic T lymphocyte responses

I have compared the requirements for T helper (Th) cell function during the generation of virus-specific and alloreactive cytotoxic thymus (T)-derived lymphocyte (CTL) responses. Restimulation of vesicular stomatitis virus (VSV)-immune T cells (VSV memory CTLs) with VSV-infected stimulators resulted in the generation of class I-restricted, VSV-specific CTLs. Progression of VSV memory CTLs (Lyt-1-2+) into VSV-specific CTLs required inductive signals derived from VSV-induced, Lyt-1+2- Th cells because: (i) cultures depleted by negative selection of Lyt-1+ T cells failed to generate CTLs; (ii) titration of VSV memory CTLs into a limiting dilution (LD) microculture system depleted of Th cells generated curves which were not consistent with a single limiting cell type; (iii) LD analysis of VSV memory CTLs did produce single-hit curves in the presence of Lyt-1+2- T cells sensitized against VSV; and (iv) monoclonal anti-L3T4 antibody completely abrogated CTL generation against VSV. Similar results were also obtained with Sendai virus (SV), a member of the paramyxovirus family. The notion that a class II-restricted, L3T4+ Th cell plays an obligatory role in the generation of CTLs against these viruses is also supported by the observation that purified T cell lymphoblasts (class II antigen negative) failed to function as antigen-presenting cells for CTL responses against VSV and SV. T cell lymphoblasts were efficiently lysed by class I-restricted, anti-VSV and -SV CTLs, indicating that activated T cells expressed the appropriate viral peptides for CTL recognition. Furthermore, heterogeneity in the VSV-induced Th cell population was detected by LD analysis, suggesting that at least two types of Th cells were required for the generation of an anti-VSV CTL response. VSV-induced Th cell function could not simply be replaced by exogenous IL-2 because this lymphokine induced cytotoxic cells that had the characteristics of lymphokine-activated killer (LAK) cells and not anti-viral CTLs. In contrast, CTL responses against allogeneic determinants could not be completely blocked with antibodies against L3T4 and depletion of L3T4+ cells did not prevent the generation of alloreactive CTLs in cultures stimulated with allogeneic spleen cells or activated T cell lymphoblasts. Thus, these studies demonstrate an obligatory requirement for an L3T4-dependent Th cell pathway for CTL responses against viruses such as VSV and SV; whereas, CTL responses against allogeneic determinants can utilize an L3T4-independent pathway.

An immunodominant class I-restricted cytotoxic T lymphocyte determinant of human immunodeficiency virus type 1 induces CD4 class II-restricted help for itself

We have observed that a peptide corresponding to an immunodominant epitope of the HIV-1 envelope protein recognized by class I MHC-restricted CD8+ CTL can also induce T cell help for itself. The help is necessary for restimulation of CTL precursors in vitro with peptide alone in the absence of exogenous lymphokines, can be removed by depletion of CD4+ T cells, and can be replaced by exogenous IL-2. Whereas the CTL in BALB/c or B10. D2 mice are restricted by the class I molecule Dd, the Th cells are restricted by the class II molecule Ad, and the help can be blocked by anti-Ad mAb. To examine the genetic regulation of the induction of help, we studied B10.A mice that share the class I Dd molecule, but have different class II molecules, Ak and Ek. Spleen cells of immune B10.A mice behave like CD4-depleted BALB/c spleen cells in that they cannot be restimulated in vitro by the peptide alone, but can with peptide plus IL-2. Therefore, in the absence of exogenous lymphokines, peptide-specific help is necessary for restimulation with this immunodominant CTL epitope peptide, and in H-2d mice, this peptide stimulates help for itself as well as CTL. We speculate on the implications of these findings for the immunodominance of this peptide in H-2d mice, and for the selective advantage of pairing certain class I and class II molecules in an MHC haplotype.

The alpha 3 domain of major histocompatibility complex class I molecules plays a critical role in cytotoxic T lymphocyte stimulation

Allogeneic major histocompatibility complex class I molecules induce strong cytotoxic T lymphocyte (CTL) responses whereas xenogeneic molecules do not. We have tested a series of mouse/human hybrid molecules for their ability to stimulate mouse CTL. The molecules with murine alpha 3 domains consistently stimulated stronger CTL responses than those with human alpha 3 domains, independent of the species origin of the N-terminal alpha 1 or alpha 2 domains. We have found that the ability of class I molecules to induce strong cytotoxic responses correlates positively with their ability to stimulate expansion of the CD8+CD4-T cell subset. The results indicate that mouse T cells can recognize class I molecules with human alpha 1 and/or alpha 2 domains, but for efficient stimulation of these T cells it is important that the immunizing molecule contains a murine alpha 3 domain. We suggest that T cell priming requires an efficient interaction of CD8 with the class I alpha 3 domain, and this shows some species restriction.

The generation and activation of memory class I MHC restricted cytotoxic T cell responses to influenza A virus in vivo do not require CD4+ T cells

The cellular requirements for the generation and activation of anti-influenza memory class I MHC restricted Tc cell responses were studied by selectively reconstituting lethally irradiated mice. The generation of memory Tc cells was investigated by using unprimed splenocytes to reconstitute infected, lethally irradiated mice; the activation of memory Tc cells was tested by using primed splenocytes to reconstitute uninfected, lethally irradiated mice. It is shown here that depletion of CD4+ T cells from donor cells did not reduce Tc cell responses in recipient mice. Depletion of CD8+ T cells from donor splenocytes prevented the memory Tc cell responses. Thus depletion of CD4+ T cells had no effect on the generation and activation of the memory Tc cells in vivo.

Intestinal graft-versus-host disease is initiated by donor T cells distinct from classic cytotoxic T lymphocytes

In these studies, the role of T helper and T cytotoxic cells in generating intestinal graft-vs.-host disease (GVHD) was examined. Treatment of C57BL/6J (B6) splenocytes with L-leucyl-L-leucine methyl ester (Leu-Leu-OMe) selectively removes natural killer cells, cytotoxic T lymphocyte (CTL) precursors, and the capacity to cause lethal GVHD in irradiated B6xDBA/2 F1 (B6D2F1) mice while preserving T helper cell function. Neither control nor Leu-Leu-OMe-treated DBA/2 donor spleen and bone marrow cells were found to induce lethal GVHD in B6D2F1 recipients. However, extensive colonic GVHD developed in B6D2F1 recipients of DBA/2 bone marrow and spleen cells. Enteropathic GVHD in DBA/2----B6D2F1 mice was reduced in severity after anti-L3T4 + C treatment of donor cells, and was eliminated by anti-Thy1.2 + C or the combination of anti-L3T4 and anti-Lyt2 + C treatment of the donor cell inoculum. However, neither anti-Lyt2 + C, Leu-Leu-OMe, nor anti-Lyt2 + C and Leu-Leu-OMe treatment of donor cells significantly decreased severity of gut GVHD. Leu-Leu-OMe treatment of DBA/2 or B6 SpC was comparably effective in preventing in vitro or in vivo generation of B6D2F1-specific CTL. These findings, therefore, demonstrate that histologically severe enteropathic GVHD does not require participation of CTL and is not always associated with high mortality rates.

T-cell clones with L3T4-positive or Lyt-2-positive phenotypes responding to mutant MHC class II antigen and inducing graft versus host reaction

Two types of T cell clones responding to mutant major histocompatibility class II antigen (Iabm12) were established from spleen cells of C57BL/6 mice: one was L3T4-positive and the other Lyt-2-positive. These two types of clones carried functionally different properties. Lyt-2+ clones were absolutely dependent on exogenous interleukin-2 for their proliferation, whereas some L3T4+ clones secreted interleukin-2 and proliferated autonomously. Both types of clones had cytotoxic activities to bm12 target cells, and Lyt-2+ clones showed stronger activities than L3T4+ clones. Lyt-2+ clones induced induration in situ, whereas the L3T4+ clones induced ulcerative reaction when injected intradermally into mice. Histologically, the L3T4+ clones caused necrosis of the epidermis or upperdermis, while the Lyt-2+ clones induced infiltration of small round cells through the epidermis to the subcutaneous tissues and caused thickening of the epidermis. These characteristic reactivities might be due to a difference in lymphokines produced by each type of T cell subset in response to Iabm12 antigen.

Xenogeneic skin graft rejection is especially dependent on CD4+ T cells

B6 mice were treated in vivo with anti-CD4, anti-CD8, or both anti-T cell antibodies together in an effort to prolong xenogeneic compared with allogeneic skin graft survival. Mice treated with anti-CD4 antibody showed prolonged survival of xenogeneic monkey or rabbit skin even after they had rejected whole MHC-disparate allogeneic mouse skin. Furthermore, the addition of cyclosporine was synergistic with the anti-CD4 antibody in prolonging graft survival. These results suggest that the cell-mediated response to xenogeneic antigens is especially dependent on CD4+ lymphocytes, a feature shared by the response to allogeneic minor histocompatibility antigens. In addition, the results suggest a possible approach to clinical immunosuppression for some forms of xenogeneic transplantation.

Ethanol: an enhancer of transplantation antigen expression

Major histocompatibility antigens (MHC) play a pivotal role in the immune response. Abnormal expression of MHC antigens has been correlated with aberrant regulation of the immune response. Studies on the effect of ethanol on class I MHC antigens demonstrate that ethanol significantly enhances their cell surface expression in a variety of cell lines in vitro. These changes in cell surface levels reflect increased intracellular protein synthesis and increased steady state mRNA levels. The effective ethanol concentrations (0.1-1.0%) are physiologically attainable. Measurement of class I MHC antigens on peripheral blood lymphocytes in a population of acutely ethanol-intoxicated patients showed a highly significant increase relative to controls. The possibility that the elevated levels of MHC antigens induced by ethanol may play a role in the evolution of ethanol-related disease is discussed.

T cell memory. Long-term persistence of virus-specific cytotoxic T cells

This study documents that virus-specific CTL can persist indefinitely in vivo. This was accomplished by transferring Thy-1.1 T cells into Thy-1.2 recipient mice to specifically identify the donor T cell population and to characterize its antigenic specificity and function by using a virus-specific CTL assay. Thy-1.1+ T cells from mice previously immunized with lymphocytic choriomeningitis virus (LCMV) were transferred into Thy-1.2 mice persistently infected with LCMV. The transferred LCMV-specific CTL (Thy-1.1+ CD8+) eliminate virus from the chronically infected carriers and persist in the recipient mice in small numbers, comprising only a minor fraction of the total T cells. Upon re-exposure to virus, these long-lived "resting" CD8+ T cells proliferate in vivo to become the predominant cell population. These donor CD8+ T cells can be recovered up to a year post-transfer and still retain antigenic specificity and biological function. They kill LCMV infected H-2-matched cells in vitro and can eliminate virus upon transfer into a second infected host. In addition, these long-lived CD8+ T cells appear not to be dependent on help from CD4+ T cells, since depletion of CD4+ T cells has minimal or no effect on their biological properties (proliferation, CTL response, viral clearance). These donor CTL also exhibit an immunodominance over the host-derived LCMV-specific CTL response. When both host and donor T cells are present, the donor CTL response is dominant over the potential CTL response of the cured carrier host. Taken together, these results suggest that virus-specific CTL can persist for the life span of the host as memory cells.

Effect of cyclosporin A on T cell immunity. II. Defective thymic education of CD4 T helper cell function in cyclosporin A-treated mice

Cyclosporin A (CsA) is an immunosuppressive agent that is widely used in transplantation. Recent animal studies indicate that CsA can affect the development of immunity so that autoreactive T lymphocytes are generated. In this study, mice were treated with CsA prior to irradiation and transplantation of syngeneic bone marrow to determine whether CsA pretreatment would affect the ability of the bone marrow recipients to develop normal T cell function. Our results indicate that (a) thymuses of CsA-treated mice do not contain single-positive thymocytes (i.e. L3T4+Ly-2- or L3T4-Ly-2+) during i.p. treatment with 15 mg/kg/day of CsA; (b) both populations of single-positive thymocytes reappear within 2 weeks of termination of CsA and (c) irradiation and bone marrow reconstitution of these CsA-treated mice results in reconstitution of normal numbers of L3T4+ and Ly-2+ cells, but the L3T4+ T cells to not provide T helper function, as determined by interleukin 2 production and cytotoxic T lymphocytes generation. These findings indicate that CsA can affect thymic microenvironment and may be important as a model for investigating intrathymic T cell maturation. Our results may also have clinical implications for T lymphocyte development in transplant patients receiving CsA.

Activated B cells can deliver help for the in vitro generation of antiviral cytotoxic T cells

The experiments described in this paper show that activated B cells can deliver help for antiviral cytotoxic T (Tc) cell responses in vitro. This conclusion is based on four observations. (i) Influenza viruses induced secondary Tc cell responses in vitro in the absence of CD4+ T cells. This capacity correlated with the B-cell mitogenicity of these viruses. (ii) Depletion of both CD4+ T cells and B cells prevented the generation of anti-influenza Tc cell responses, whereas depletion of either CD4+ T cells or B cells alone failed to do so. In addition, supplementation of unprimed B cells restored the Tc cell responsiveness of primed splenocytes that had been depleted of both CD4+ T cells and B cells. (iii) Contact between T and B cells was not obligatory for the delivery of B-cell helper signal, and hence help was mediated by a soluble factor(s). (iv) Lipopolysaccharide-activated B cells could replace the CD4+ T-cell requirement in the induction of Tc cell responses to nonmitogenic influenza virus in vitro.

Virus-specific cytotoxic T lymphocytes in multiple sclerosis: a normal mumps virus response adds support for a distinct impairment in the measles virus response

An impairment of the measles virus-specific cytotoxic T lymphocyte response in multiple sclerosis was previously reported. This response is predominantly mediated by HLA class II-restricted CD4+ cells. In the present report, virus-specific cytotoxic T lymphocyte responses in multiple sclerosis were further studied by examining the response to mumps virus. No significant difference was detected in the generation of mumps virus-specific cytotoxic T lymphocyte responses between normal individuals and multiple sclerosis patients with impaired measles virus-specific cytotoxicity. A portion of the mumps virus-specific cytotoxic T lymphocyte response could be mediated by HLA class II-restricted CD4+ cells generated from both normal controls and MS patients. This CD4+ cell-mediated portion of the response was similar in both groups. These findings support the view that there is a distinct measles virus-specific impairment in cell-mediated cytotoxicity in multiple sclerosis.

In vivo administration of Fab' fragments of anti-L3T4 (GK1.5) antibody inhibits the T helper cell function of murine lymph node cells

The effect of intravenous injection of Fab' fragments of anti-L3T4 antibody (GK1.5 monoclonal antibody) into mice was studied. This treatment depleted L3T4+ cells from the popliteal lymph nodes of keyhole-limpet hemocyanin-primed mice. The T cells that remained were unable to provide help to antigen-specific B cells in vitro. The results obtained using Fab' fragments were comparable with those using intact anti-L3T4 antibody and demonstrate that either form of GK1.5 is a potentially useful immunosuppressive agent in mice.

Modulation of MHC class I antigen decreases pancreatic islet immunogenicity

Pretreatment regimens directed at reducing the immunogenicity of pancreatic islets have emphasized the elimination or alteration of the major histocompatibility complex (MHC) class II-positive dendritic cells within the islet. Unfortunately, the efficacy of such pretreatment regimens has been extremely variable and the relative contribution of the dendritic cells to the overall immunogenicity of pancreatic islets has remained ambiguous. Recent evidence has suggested that the MHC class I antigen present on the endocrine cells within the islets may play an important role in the alloimmune response. This study utilized the in vitro mixed lymphocyte-islet co-culture system to determine if pretreatment of whole islets with an anti-MHC class I monoclonal antibody specific to the donor strain would block the generation of cytotoxic T lymphocytes (CTL) in the in vitro mixed lymphocyte-islet coculture. Pretreatment of B10.BR (H-2k) and DBA/2J (H-2d) islets with an allospecific anti-MHC class I monoclonal antibody blocked the generation of allospecific CTL when the pretreated islets were placed into coculture with C57Bl/6 (H-2b) splenocytes. If such a pretreatment regimen is similarly effective in vivo, it could potentially be used as an antirejection strategy in pancreatic islet allotransplantation.

Responsiveness of T cells to mutant major histocompatibility complex class I antigen. II. Role of stimulator-type accessory cells with reference to interleukin 1 production

Mechanisms of the activation of T cells responding to major histocompatibility complex (MHC) class I antigen were investigated with special reference to interleukin 1 (IL-1) production from stimulator-type accessory cells. For this purpose, we used mainly fractionated Lyt-2+T cells of C57BL/6 (B6) mice as responder cells and irradiated spleen cells or those deprived of adherent cells of B6.C-H-2bm1 (bm1) mice as stimulator cells. Lyt-2+ T cells of B6 mice proliferated in the presence of irradiated whole spleen cells of bm1 mice but did not to Sephadex G-10 column-passed bm1 spleen cells. The unresponsiveness in the latter case was overcome by the supplement of recombinant IL-1 and/or IL-2 in the culture medium. These interleukins were shown to promote the proliferative response of B6 Lyt-2+ T cells in the presence of stimulator-type T or B cells. Both interleukins also facilitated the generation of cytotoxic T cells from B6 Lyt-2+ cells to H-2Kbm1 antigen in the mixed lymphocyte culture deficient in stimulator-type accessory cells. IL-1 was shown to enhance the expression of IL-2 receptor on the responding Lyt-2+ T cells as assessed by flow cytometry. IL-1 binding to responding T cells were also assayed by means of iodinated IL-1 and was shown to increase significantly on responding Lyt-2+ cells. Overall results indicate that accessory cells might play dual roles in the activation of Lyt-2+ T cells responding to allogeneic MHC class I antigen: direct presentation of the antigen to responder T cells and production of IL-1. Both signals are essentially required for Lyt-2+ T cells responding to allogeneic MHC class I antigen to initiate proliferation and also to differentiate into cytotoxic T cells.

Effect of cyclosporin A on T cell immunity. I. Dose-dependent suppression of different murine T helper cell pathways

Cyclosporin A (CsA) is used as a clinical immunosuppressive agent. Despite its immunosuppressive potential, some studies involving in vivo administration of cyclosporin have failed to verify the immunosuppressive activity of this agent. The present study investigates the effect of different concentrations of CsA added in vitro, or of different doses of CsA administered in vivo, on the ability of murine spleen cells to produce interleukin 2 and to generate cytotoxic T lymphocytes in vitro when stimulated with TNP-self or H-2 alloantigens. The results indicate that self Ia-restricted T helper (Th) cells are more sensitive to lower doses of CsA than Th cells that are allorestricted. Thus, doses of CsA were found (15-30 mg/kg) that inactivated self Ia-restricted Th function, but not other Th or effector function. This Th cell defect could be partially corrected in vitro by addition of Th cell factors to the sensitization cultures. A higher dose (75 mg/kg) of CsA inactivated all detectable T cell responses, and this defect was not corrected by addition of Th cell factors. T cell function returned to normal levels within two weeks of cessation of CsA at all three doses of CsA tested. The selective loss of L3T4 Th function at the lower doses of CsA was associated with a radiosensitive, Ly-2 suppressor T cell that was selective in its action on self Ia-restricted Th cell function. Loss of all T cell function at the higher dose of CsA was associated with a radioresistant non-T suppressor cell that inactivated all T cell function tested. These results are discussed with respect to the selective dose-dependent effects of CsA on Th subsets, on the activation of suppressor cells with similar selectivity, and the implications of these findings on the use of CsA to prevent rejection of tissue allografts.

Reconstitution of cytolytic alloreactivity with N-[4-[(4-fluorophenyl) sulfonyl]phenyl]acetamide (CL 259,763) in animals immunocompromised by cyclophosphamide

A novel synthetic immunopotentiator, i.e. N-[4-[(4-fluorophenyl)sulfonyl]phenyl]acetamide (CL 259,763), was investigated for its potential in reconstituting the cell-mediated immune response of animals whose immunologic system had been severely depressed by cytoreductive agents. It was demonstrated that lymphocytes from mice which had received 300 mg/kg of cyclophosphamide (CY) immediately following antigen sensitization had a reduced capability of responding to alloantigens in mixed lymphocyte culture and failed to generate effective cytolytic T-lymphocytes (CTL) capable of destroying appropriate tumor target cells in a cytotoxicity assay. However, treatment of these immunocompromised animals with CL 259,763 produced a significant restoration of alloreactivity, as evidenced by an enhancement of the CTL response. Although effective doses of CL 259,763 ranged from 20 to 300 mg/kg, the optimal effect was observed at 75 mg/kg. Findings from a time course study indicated that the maximum restoration occurred when CL 259,763 was given to mice 2-5 days after, but not before or simultaneously with, CY treatment. Both the immunoimpairment by CY and its reversal by CL 259,763 appeared not to be antigen specific. The lessened immunoreactivity of CY-treated mice was explicable by the presence of suppressor cells in their spleens. These suppressors were able to adhere to plastic and resisted treatment with anti-Thy 1.2 antibody, indicating a macrophage characteristic. Flow cytometric analysis indicated a quantitative depletion of all T-lymphocytes, including Thy-1.2(+), Lyt-1(+), Lyt-2(+) and L3T4(+) subsets in the spleens of CY-treated mice; however, a population of Mac-1(+) cells was markedly expanded.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence of increased class I MHC expression on human peripheral blood lymphocytes during acute ethanol intoxication

Certain ethanol-related diseases in humans have been linked to disorders of immunity. Although humoral and cellular immunity have been studied, the precise mechanisms whereby ethanol use leads to tissue damage remain unknown. In order to explore the hypothesis that ethanol may lead to alteration in expression of tissue Class I major histocompatibility antigen causing an autoimmune phenomenon, a population of acutely ethanol-intoxicated patients was studied. Measurement of Class I major histocompatibility antigen on peripheral blood lymphocytes in this population showed a highly significant (p less than 0.01) increase over controls. The role that this increased antigenicity may play in the evolution of clinical disease is discussed.

Helper strategy in tumor immunology: expansion of helper lymphocytes and utilization of helper lymphokines for experimental and clinical immunotherapy

Two main kinds of immune strategy are possible against neoplasia. The first potentiates a selected effector arm. In vitro culture with exogenous interleukin-2 (IL-2) increases the activity of natural killer cells and leads to the expansion of T cytotoxic lymphocytes. Systemic reinfusion of both of these cells with high doses of IL-2 mediates the regression of a variety of murine and human tumors. In an alternative strategy, a few regulatory lymphocytes turn on immune reactivity by triggering a cascade of interconnected effector functions. The efficacy of this strategy rests on the repertoire of effector mechanisms moved to action. An effective immunoregulatory maneuver is the addition of helper determinants on the surface of tumor cells. Its power can be further increased by the pre-induction of helper T lymphocytes specific to the helper determinants. This approach can be achieved in mice by coupling muramyl dipeptides to tumor cells, along with eliciting T lymphocytes specifically reactive to Bacillus Calmette-Guerin. Noncytotoxic T helper lymphocytes produce factors which recruit nonspecific (macrophages) as well as specific (cytolytic T lymphocytes) anti-tumor attacking cells. In this way protection can be afforded against primary tumors and metastases, as well as leukemia cells. As the activity of helper lymphocytes rests mostly on lymphokine release, the use of molecularly defined lymphokines mimicking T-helper functions has also been attempted. In a few experimental models, the association of low doses of IL-2 with non-reactive lymphocytes from tumor-bearing mice promotes an effective anti-tumor reaction in the host. Moreover, the combination of distinct lymphokines can also build a molecularly defined helper system able to activate in sequence non-specific and specific anti-tumor reactions in vivo. Trials intended to evaluate the clinical impact of these helper approaches in the management of human tumors are being started or are already under way.