Effects of blocking helper T cell induction in vivo with anti-Ia antibodies. Possible role of I-A/E hybrid molecules as restriction elements

The discovery of T cell help for B cell antibody formation: a perspective from the 30th anniversary of this discovery

Thirty years ago, Miller and Mitchell described the bone-marrow origin of antibody-forming cells and the thymic origin of the help needed to activate the bone-marrow-derived antibody formation. Since then, there has been a continuous stream of discovery in Australia, from Zinkernagel and Doherty's description of MHC-restricted antigen recognition to Goodnow's dissection of the maturation and tolerization of antigen-specific B cells. All of these discoveries, and many more described in the text, contribute to the modern synthesis in immunology.

Vaccination with peptides from MHC class II beta chain hypervariable region causes allele-specific suppression of EAE

In our earlier studies we showed that successful immunotherapy of EAE in SJL/J mice can be achieved either by the use of antibodies to MHC class II antigens or by vaccination with synthetic peptide analogs of the beta chain of MHC class II molecules. We proposed that inhibition of EAE following vaccination with synthetic peptides derived from the beta chain of mouse I-A, was in part due to the generation of auto-anti-MHC class II antibodies that interfered with T cell sensitization. In our present study we show that suppression of EAE following vaccination results in poor sensitization of MBP reactive T cells, and that the lack of immune response is allele-specific. In F1(SJL(I-AS) x Balb/cI-Ad) mice, in which susceptibility to EAE is linked closely to the I-AS allele, vaccination with peptides from beta chain of I-AS results in inhibition of proliferative response to MBP and prevents the development of EAE. Vaccination with peptide from the beta chain of I-Ad did not affect either the development of immune response to MBP or the induction of EAE, indicating allele-specific suppression. Since global immunosuppression is not induced by vaccination with I-A peptides, we propose that this strategy can be extended to human autoimmune diseases wherein a clear association between certain MHC class II alleles and autoimmune disease is evident.

Antigen-specific tolerance as a therapy for experimental autoimmune encephalomyelitis

The effects of neuroantigen-specific tolerance on the induction and effector stages of EAE were examined. Tolerance induced by the i.v. injection of syngeneic splenocytes coupled with purified neuroantigens or encephalitogenic peptides of MBP and PLP using ethylene carbodiimide was extremely effective in both prevention and treatment of acute and relapsing forms of EAE in Lewis rats and SJL/J mice. The unresponsiveness is rapidly-induced, dose-dependent, long-lasting, efficient, MHC class II-restricted, and exquisitely antigen-specific. This procedure targets only effector cells bearing clonotypic receptors specific for the autoantigen/autoepitope and thus does not depend upon the autoimmune response being dominated by a restricted T cell repertoire. Moreover, it does not require that the response to the autoantigen be dominated by recognition of a specific epitope(s) within a particular autoantigen, or even the identification of the specific autoantigen. The results also demonstrate the usefulness of peripheral tolerance induced by antigen-coupled syngeneic splenocytes for identifying the fine specificity of autoimmune T cell responses which appear to change during the progression of relapsing EAE. Thus, this technique offers major advantages over many other currently employed immunoregulatory strategies and is therefore relevant for establishment of therapeutic protocols for the antigen-specific treatment of human T cell-dependent autoimmune disorders.

Haplotype-specific inhibition of homing of radiolabeled lymphocytes in experimental allergic encephalomyelitis following treatment with anti-IA antibodies

In vivo treatment with anti-IA antibodies has been shown to induce a haplotype-specific inhibition of EAE when the disease was following passive transfer of MBP-sensitized T cells. In order to determine the mechanism by which anti-IA antibody prevents passively transferred EAE, the homing of radiolabeled cells to the brain following anti-IA therapy was studied. Administration of anti-IA antibodies at the earliest onset of clinical signs of EAE prevented the homing of radio-labeled cells to the brain. In F1 (Balb/c x SJL/J) mice that developed EAE and received anti-IAs antibody there was a decreased homing of radiolabeled cells when compared to animals that received anti-IAd antibody. In addition, there was preferential expression of IAs antigen, over IAd antigen on capillary endothelium of the brain. The differential expression of IA antigens and the homing of radiolabeled cells in F1 (SJL x Balb/c) mice could in part explain the haplotype-specific suppression of disease following treatment with anti-IA antibodies.

Disparate functions of I-A and I-E molecules on B cells as evidenced by the inhibition with anti-I-A and anti-I-E antibodies of polyclonal B cell activation

Polyclonal differentiation of unprimed B cells into IgM-producing cells induced by lipopolysaccharide (LPS) or T cell-derived lymphokine B151-TRF2 has been shown to contain a process of I-A-restricted B-B cell interaction, so that the B cell responses are inhibited by monoclonal antibodies (mAb) specific for I-A molecules. On the other hand, the B cell responses are also inhibited by anti-I-E mAb, although I-E molecules are not involved in such B-B cell interaction. In this study, we examined the mechanism underlying the anti-I-E-mediated inhibition of the B cell responses. The B cell responses induced by LPS or B151-TRF2 were inhibited by either anti-I-A or anti-I-E mAb added on day 0 over a 5-day culture period, whereas when added on day 3 the responses were inhibited only by anti-I-E mAb and not by anti-I-A mAb. To gain insight into the mechanism underlying the anti-I-E-mediated inhibition, we prepared monovalent Fab and divalent F(ab')2 fragments of anti-I-A and anti-I-E mAb and examined their effects on the B cell responses. We found that the B cell responses were inhibited by the F(ab')2 but not Fab fragment of anti-I-E mAb, whereas the Fab fragment of anti-I-A mAb still gave effective inhibition. The F(ab')2 but not Fab fragment of anti-I-E mAb induced increases in cyclic AMP (cAMP) levels in B cells, whereas the undigested anti-I-A mAb did not induce such increases. Furthermore, adenylate cyclase inhibitors, which inhibit cellular cAMP accumulation, circumvented the B cell responses inhibited by anti-I-E but not anti-I-A mAb. Thus, these results indicate that the anti-I-E-mediated inhibition of the B cell responses requires increases in intracellular cAMP levels induced by cross-linking of I-E molecules. In contrast, anti-I-A mAb inhibits the B cell responses without cross-linking of I-A molecules and cAMP accumulation. These results reinforce a unique function of I-A molecules as restriction elements in the Ia-restricted B-B cell interaction.

Masking of veto function in vivo by activated CD4+ T lymphocytes

Donor CD8+ T lymphocytes injected into recipient mice incompatible at major histocompatibility complex (MHC) class I genes induce donor-specific CTL nonresponsiveness, attributed to the veto function of donor cells. Here we show that conditions leading to strong activation of CD4+ T cells, namely the presence in the recipient of foreign MHC class II determinants, lead to the apparent loss of veto function of donor cells. This "masking" of veto function is dependent on the dose of foreign MHC class II present. Veto function can be partially restored by treatment of recipients in vivo with CD4-specific antibody, a measure which has been shown to eliminate the function of CD4+ T cells in vivo. We conclude that CD4+ T cells activated by contact with antigen can interfere with the veto function of CD8+ T cells. Consequences of this finding are: (a) veto function of a sample cell population can be overlooked when activation of CD4+ T cells occurs simultaneously. (b) The balance between veto function of recipient cells and its abrogation might be responsible for the kind of graft-vs.-host reaction generated (CD8+ T cell-mediated and frequently lethal or CD4+ T cell-mediated and not lethal) when parental T cells are injected into recipients incompatible at MHC class I and class II genes. (c) A possible contribution of veto cells should be considered in several protocols in which donor hemopoetic cells were used in conjunction with CD4-specific antibodies to induce transplantation tolerance. (d) Veto function in vivo does not require a contribution of CD4+ T cells.

Correlation between increase in Ia-bearing macrophages and induction of T cell-dependent antitumor activity by Lactobacillus casei in mice

When Lactobacillus casei YIT 9018 (LC 9018) or Corynebacterium parvum, known to be immunomodulators possessing antitumor activity, were injected i.p. into BALB/c mice, peritoneal exudate macrophage Ia antigen detected by indirect immunofluorescence method was expressed on their cell surface, but it was not expressed following the injection of 10% proteose peptone, an inflammatory agent, or Lactobacillus fermentum YIT 0159 (LF 0159), which have no antitumor activity. The percentage and absolute number of Ia-positive peritoneal macrophages were maximum on the 7th day after the injection of LC 9018. Immunization by injection of Meth A fibrosarcoma cells treated with mitomycin C (MMC-Meth A) 7 days after LC 9018 injection suppressed the growth of Meth A implanted i.p. 14 days after MMC-Meth A injection. A shorter interval between the injections of LC 9018 and MMC-Meth A did not allow suppression of Meth A growth. These results showed that the increase in Ia-positive macrophages in the peritoneal cavity coincided with the effective interval for induction of the antitumor activity by LC 9018. The antitumor activity induced by injections of LC 9018 and MMC-Meth A did not affect the growth of RL male 1 leukemic cells, syngeneic to BALB/c mice. Neutralization (Winn type) tests showed that peritoneal T lymphocytes possessed tumor cytotoxicity and that the antitumor capacity was reduced by in vivo treatment with anti I-Ad monoclonal antibody simultaneously with and 1 day prior to MMC-Meth A injection. These results indicate that LC 9018-induced Ia-positive macrophages, which first encounter a tumor antigen in the peritoneal cavity, play an important role in the in vivo induction of tumor specific T cell-mediated antitumor immunity.

Immunomodulation of murine visceral leishmaniasis by administration of monoclonal anti-Ia antibodies: differential effects of anti-I-A vs. anti-I-E antibodies

On a B10 genetic background noncure and cure phenotypes for murine visceral leishmaniasis are controlled by H-2. In this report results are presented which show the effects of administering specific anti-I-A and anti-I-E monoclonal antibodies to B10.D2/n (H-2d) noncure mice prior to and during 85 days of infection with Leishmania donovani LV9. The effects of the two anti-Ia antibodies were precisely equivalent in diminishing circulating anti-leishmanial IgG levels throughout infection, possibly as a direct effect of the anti-Ia antibodies in reducing the splenic B cell population. In terms of resolution of liver and spleen parasite loads, which is known to be dependent upon induction of a cell-mediated immune response, dramatically different results were obtained with the two anti-Ia antibodies. Anti-I-A treatment resulted in prolonged exacerbation of disease in liver and spleen. Anti-I-E treatment was associated with enhanced clearance of liver and spleen parasite loads beyond 30 days of infection. The results are consistent with the hypothesis that blocking major histocompatibility complex-restricted antigen presentation by one class II molecule allows T cell responses controlled by the other to predominate. Hence, in H-2d mice, I-E controls suppressor activity while I-A is associated with helper activity for cell-mediated control of infection. The results offer some prospect for the development of haplotype- and class II molecule-specific immunotherapeutic regimens in the host which might prevent the undesirable expansion of T cell populations which exacerbate disease without compromising development of a curative cell-mediated immune response.

Inhibition of experimental autoimmune thyroiditis in mice by anti-I-A antibodies

Experimental autoimmune thyroiditis is induced in mice by immunization with thyroglobulin emulsified in Freund's complete adjuvant. The disease is characterized both by thyroid infiltration with mononuclear cells and by circulating thyroglobulin antibodies. The magnitude of the thyroid infiltration and the titer of thyroglobulin antibodies are controlled by genes in the I-A subregion of the major histocompatibility complex (H-2). We investigated the in vivo effect of monoclonal anti-Ia antibodies on experimental autoimmune thyroiditis in susceptible mice. Antibodies were given around the time of immunization, later after immunization, and to mice with established disease. Monoclonal antibody produced by the hybridoma line 10-3.6 (anti-I-Ak, s, u, v, z, f) completely prevented both production of thyroglobulin antibodies and thyroid infiltrates, when given shortly before or at the time of antigen administration. This effect was dose-dependent and this monoclonal antibody decreased the severity of the disease when given after the antigen challenge but did not fully suppress established thyroiditis. The same antibody markedly decreased the number of B lymphocytes in the spleen and decreased the thyroglobulin-induced spleen cell proliferation when either given in vivo or added in vitro to cell cultures. Antibodies produced by the hybridoma line 11.2.12 (anti-I-Ak) did not show an inhibitory effect on the disease. These experiments suggest that in this model of murine thyroiditis anti-Ia antibodies act on antigen-presenting cells. Furthermore, only one monoclonal antibody, anti-Ia, suppressed the immune response to thyroglobulin, suggesting a possible role for the isotype and specificity of anti-Ia antibody.

Monoclonal anti-Ia antibodies suppress the flare up reaction of antigen induced arthritis in mice

Intravenous injection of methylated bovine serum albumin (mBSA) in mice with a unilateral antigen-induced arthritis induced with mBSA causes a flare up of the inflammation in the arthritic but not in the contralateral joint. To study whether this phenomenon is dependent on class II antigens, we treated C57Bl/10 (H-2b) and C3H (H-2k) mice with monoclonal anti-Iab (HB26) and anti-Iak (2-2-1) antibodies on days -3, -2, -1 and 0 before induction of the flare up. Another group was treated only once on day 0 before antigen challenge. Four injections with HB26 completely suppressed the flare up reaction in C57Bl/10 mice; the same results were seen with 2-2-1 in C3H mice. One injection only partly suppressed the flare up reaction in both strains, whereas four injections with the haplotype-nonspecific antibodies did not affect the flare up. Injections with HB26 appeared to be able to completely suppress a delayed type hypersensitivity reaction but not a reversed passive Arthus reaction in C57B1/10 mice, indicating that anti-Ia antibodies have an effect on lymphocyte-dependent but not on antigen-antibody-dependent inflammatory phenomena. These results demonstrate that the flare up of antigen induced arthritis is dependent on the presence of Ia antigens, suggesting that the interaction between antigen-presenting cells and T lymphocytes plays an important role in this process.

In vivo growth inhibition of Ia+ lymphomas in SJL mice treated with I-As-reactive monoclonal antibody

SJL/J mice injected with a syngeneic, I-As-positive transplantable lymphoma (RCS) and treated with I-As-reactive monoclonal antibody (McAb) for one week showed reduced tumor growth in peripheral lymph nodes and spleen when compared to untreated controls. The effect of McAb on RCS growth was observed after treatment with I-As McAb derived from two different hybridomas, but similar growth inhibition did not occur in RCS-injected mice treated with a non-cross-reacting I-Ab McAb. Specificity of the effect was also indicated by the observation that partial absorption of I-As McAb with I-As-positive cells decreased its ability to reduce tumor growth in RCS-injected SJL recipients. In parallel experiments in which McAb treatment was stopped after one week, RCS-injected mice survived up to 8 times longer (80 days) than untreated control mice, which died by day 10 after tumor cell inoculation. Although the precise mechanism(s) by which McAb treatment influences RCS growth has not been fully characterized, it is likely that I-As McAb may block the characteristic T cell proliferative response to I-A antigens on RCS cells that appears necessary for progressive tumor growth in vivo. Absence of such host immune recognition could result in either a deficiency in production of RCS growth-promoting lymphokines or induction of effector cells capable of inhibiting tumor growth.

Effect of anti-Ia treatment on the production of anti-DNA antibody by NZB mice

A cell transfer system was used to study the effect of anti-Ia antibodies on anti-DNA-producing B cells. B cells from autoimmune New Zealand Black (NZB) mice were necessary and sufficient to transfer anti-DNA antibody production to congenic NZB. xid recipients. Anti-Ia treatment of either donors or recipients led to a significant reduction in the number of B cells secreting anti-DNA antibody. This effect was detectable after as little as 3 days of treatment and persisted for at least 1 month after the cessation of therapy. In this system, we could find no evidence of suppressor cell induction. These data suggest that anti-Ia antibodies directly suppress autoantibody-producing B lymphocytes.

Characteristics of a T lymphocyte-enhancing Ab-specific monoclonal antibody. I. Genetic specificity and preferential enhancement of allogeneic reactions

We recently described the production and characterization of an Ab-specific monoclonal antibody (mAb), designated K14.83-11, which specifically enhanced the alloreactivity of normal T lymphocytes, as well as highly selected Ab-specific T-cell lines and clones against the appropriate Ab molecule. In the present report, we have studied both the binding specificity and immunoenhancing activity of K14.83-11 in a number of genetic combinations to better characterize the possible modes through which this mAb achieves its T cell-enhancing activity. Results reported here (1) confirm and extend previous findings revealing the possible importance of the immunoglobulin G3 isotype of K14.83-11 in its immunoenhancing activity, and (2) show a distinction in the determinant binding and subsequent ability to elicit an enhancing effect. Surprisingly, K14.83-11 proved ineffective in enhancing autologous or Ab-restricted reactions. This system, then, may provide the means of comparing the functional importance of Ab expression in self-restricted and allogeneic reactions.

Possible involvement of transglutaminase in endocytosis and antigen presentation

Experiments were carried out to determine as to whether or not internalization of antigen is necessary for subsequent antigen presentation by accessory cells using monoamines which are known as transglutaminase (TGase) inhibitors. It was found that endocytosis for immune complexes via Fc receptors such as sheep erythrocytes coated with IgG class antibody (EA) was different from receptor-independent endocytosis for soluble protein such as horse radish peroxidase (HRP) in the sensitivity to monoamines; methylamine inhibited the receptor-dependent endocytosis of immune complexes at a concentration of over 20 mM and the receptor-independent endocytosis of HRP at 2 mM, while dansylcadaverine (DC) inhibited both at a concentration of 100 microM. It was noteworthy that antigen-specific T cell proliferation to splenic adherent cells pulsed with DNP9.6-ovalbumin (DNP9.6-OVA) was blocked strongly by DC as well, but weakly by methylamine. These results suggest the possibility that antigen presentation requires internalization of antigen by a mechanism such as receptor-dependent endocytosis for the subsequent reexpression of antigen on membranes. Furthermore, it was confirmed that TGase activity is high in peritoneal exudate and spleen adherent cells, both of which have accessory cell activities for lymphocytes, suggesting the possibility that TGase might be involved intimately in receptor-dependent endocytosis and subsequent antigen presentation.

In vivo effects of GK1.5 (anti-L3T4a) monoclonal antibody on induction and expression of delayed-type hypersensitivity

The in vivo effects of monoclonal GK1.5 antibody, directed against the L3T4a determinant expressed on Class II-restricted T cells, on the induction and expression of murine delayed-type hypersensitivity (DTH) responses were examined. Development and expression of both hapten (2,4-dinitrofluorobenzene and 2,4,6-trinitrochlorobenzene)- and protein antigen poly(Glu60Ala30Tyr10)-specific DTH are significantly inhibited by injection of monoclonal anti-L3T4a antibody. The inhibitory effects of anti-L3T4a were most pronounced when administered during the afferent (induction) phase of the DTH response, leading to the functional inhibition of the generation of both polyclonal lymph node T-proliferative cells (Tprlf) and DTH effector cells (TDH). The in vivo inhibitory effect is apparently unrelated to preferential induction of suppressor T cells as GK1.5 inhibited DTH induction in cyclophosphamide-treated as well as normal recipients. L3T4a expression on the various T-cell subsets involved in DTH induction and elicitation was also examined. The data show that three functionally distinct, antigen-specific T-cell subsets, Tprlf, TDH, and Th cells involved in DTH induction, bear the Lyt 1+2-, L3T4+ phenotype. Possible mechanisms where in vivo injection of anti-L3T4a inhibits Class II-restricted T-cell subsets involved in DTH induction and expression, including immune depletion and inhibition of T-cell-receptor/ligand interactions, are discussed.

Activation in vivo of a major antisuppressor T-cell pathway immediately after immunization. I. Its regulation by I-A gene products

It has previously been demonstrated that within 6 hr after immunogenic stimulation the serum of mice contains a unique form of immunogenic antigen which represents complexes of Ig and antigen. The complexes are known to be strongly cytophilic for Ly2+ Ia+ FcR+ T cells and markedly enhance the IgG response. Anti-I-A treatment of mice suppresses the IgG antibody response and results in the generation of antigen specific T suppressor cells (Ts). Furthermore, anti-I-A treatment blocks the induction of the complexes and abolishes the enhancing effect the complexes exert on the IgG antibody response. The 6-hr cytophilic complexes were shown to block the function of Ts and allow a normal IgG response to take place; therefore, they act as mediators of a novel T-cell pathway called antisuppression. The blocking of the induction of the antisuppressor complexes by anti-I-A antibody was at least in part due to an effect on T cells. In conclusion, products of genes of the I-A subregion of the MHC control the activation early after immunization of a T-cell pathway which is called antisuppression since its major function is interference with the expression of suppression. Its early induction (within 6 hr) suggests that antisuppression may play a pivotal role in determining between immunity and unresponsiveness.

Immunohistology of lymphoid and non-lymphoid cells in the thymus in relation to T lymphocyte differentiation

The present paper reports the distribution of lymphoid and non-lymphoid cell types in the thymus of mice. To this purpose, we employed scanning electron microscopy and immunohistology. For immunohistology we used the immunoperoxidase method and incubated frozen sections of the thymus with 1) monoclonal antibodies detecting cell-surface-differentiation antigens on lymphoid cells, such as Thy-1, T-200, Lyt-1, Lyt-2, and MEL-14; 2) monoclonal antibodies detecting the major histocompatibility (MHC) antigens, H-2K, I-A, I-E, and H-2D; and 3) monoclonal antibodies directed against cell-surface antigens associated with cells of the mononuclear phagocyte system, such as Mac-1, Mac-2, and Mac-3. The results of this study indicate that subsets of T lymphocytes are not randomly distributed throughout the thymic parenchyma; rather they are localized in discrete domains. Two major and four minor subpopulations of thymocytes can be detected in frozen sections of the thymus: 1) the majority of cortical thymocytes are strongly Thy-1+ (positive), strongly T-200+, variable in Lyt-1 expression, and strongly Lyt-2+; 2) the majority of medullary thymocytes are weakly Thy-1+, strongly T-200+, strongly Lyt-1+, and Lyt-2- (negative); 3) a minority of medullary cells are weakly Thy-1+, T-200+, strongly Lyt-1+, and strongly Lyt-2+; 4) a small subpopulation of subcapsular lymphoblasts is Thy-1+, T-200+, and negative for the expression of Lyt-1 and Lyt-2 antigens; 5) a small subpopulation of subcapsular lymphoblasts is only Thy-1+ but T-200- and Lyt-; and 6) a small subpopulation of subcapsular lymphoblasts is negative for all antisera tested. Surprisingly, a few individual cells in the thymic cortex, but not in the medulla, react with antibodies directed to MEL-14, a receptor involved in the homing of lymphocytes in peripheral lymphoid organs. MHC antigens (I-A, I-E, H-2K) are mainly expressed on stromal cells in the thymus, as well as on medullary thymocytes. H-2D is also expressed at a low density on cortical thymocytes. In general, anti-MHC antibodies reveal epithelial-reticular cells in the thymic cortex, in a fine dendritic staining pattern. In the medulla, the labeling pattern is more confluent and most probably associated with bone-marrow-derived interdigitating reticular cells and medullary thymocytes. We discuss the distribution of the various lymphoid and non-lymphoid subpopulations within the thymic parenchyma in relation to recently published data on the differentiation of T lymphocytes.

Disappearance and reappearance of B cells after in vivo treatment with monoclonal anti-I-A antibodies

Previous studies have shown that treatment with antibodies to the murine I-A antigen encoded in the major histocompatibility complex attenuates experimental allergic encephalitis and experimental autoimmune myasthenia gravis. These studies were conducted with SJL mice, an inbred strain that is highly susceptible to the induction of these diseases. Here we show that injection of monoclonal anti-I-A antibody in the amounts used for the above studies rapidly depletes B cells. Fluorescence-activated cell sorter (FACS) multiparameter analysis of the B-cell subpopulations in treated animals shows that maximum depletion occurs around 5 days after treatment and that recovery of some subpopulations i still incomplete 1 month later. SJL mice are more sensitive to this B-cell depletion and recover more slowly than putatively normal C3H.Ighb (CKB) mice. Some components of the primary, secondary and tertiary IgG antibody responses are reduced in anti-I-A-treated SJL animals immunized after the first and second anti-I-A injections. The persistence of some antibody response impairment well beyond the time when anti-I-A disappears raises a note of caution concerning human therapy protocols based on the injection of anti-Ia antibodies.

Treatment of (NZB x NZW)F1 disease with anti-I-A monoclonal antibodies

(NZB x NZW)F1 mice spontaneously develop an autoimmune syndrome characterized by a fatal immune complex glomerulonephritis. Administration of monoclonal antibodies specific for an I region gene product (I-Az) of the H-2 haplotype associated with susceptibility to glomerulonephritis in these animals produced a remission in female mice with established renal disease. The results demonstrated that anti-I-A therapy stabilized the level of proteinuria and increased the 1-yr survival rate from 10% to greater than 90% in treated animals relative to control mice. These findings may ultimately have therapeutic potential for the treatment of systemic lupus erythematosus.

Early development of the T cell repertoire. In vivo treatment of neonatal mice with anti-Ia antibodies interferes with differentiation of I-restricted T cells but not K/D-restricted T cells

Monoclonal antibodies to I-Ak were injected into neonatal H-2k mice for a period of 3 wk. The spleens of such mice are devoid of Ia-positive cells. Allo- and trinitrophenyl (TNP)-self-specific cytotoxic T lymphocyte (CTL) responses in such anti-I-A-treated mice were almost completely abrogated at the end of the 2-3 wk in vivo treatment period. Development of suppressor cells, carry-over of blocking antibodies, lack of responder accessory cells, or defective CTL function were not responsible for the observed defect. As concanavalin A supernatant could restore the defect, it is more likely that the defect is due to the absence of competent Ia-specific T helper cells. In addition, anti-I-A-treated mice exhibit reduced I-A antigen expression in the thymus and defective Ia-bearing accessory cell function in the spleen. It is postulated that, for development of Ia-specific T cells to occur, precursor T cells need to interact with Ia-encoded products in the thymus, and anti-Ia treatment interferes with this process. Finally, the mechanism of this interference was shown to be due to actual removal or functional inactivation of those I-A-positive elements responsible for the education of I-A-recognizing T cells, since in (H-2b X H-2k)F1 mice, treatment with anti-I-Ak antibodies results in abrogation of CTL responses to TNP in association with both parental haplotypes, while in the thymus of these mice expression of both I-Ak and I-Ab was reduced.

In vivo therapy with monoclonal anti-I-A antibody suppresses immune responses to acetylcholine receptor

A monoclonal antibody to I-A gene products of the immune response gene complex attenuates both humoral and cellular responses to acetylcholine receptor and appears to suppress clinical manifestations of experimental autoimmune myasthenia gravis. This demonstrates that use of antibodies against immune response gene products that are associated with susceptibility to disease may be feasible for therapy in autoimmune conditions such as myasthenia gravis.

Suppressor mechanisms in tumor immunity

There are many parallels between T cell-mediated suppression of tumor immunity and suppression of immune responses to haptens and polypeptides. We propose a cell interaction model which takes this into account and outlines a regulatory pathway for suppression of immunity to tumor antigens. Free antigen or antigen/antibody complexes trigger an inducer T cell subset, Tsi, which is tumor-specific. This cell activates a non-immune T cell population, pre Tse, to generate effector suppressor cells, Tse. The Tse are specific for either the idiotype of Tsi or for antigen complexed with a soluble factor made by the Tsi, but the suppression they mediate is antigenically nonspecific. Tumor antigen-specific suppressor factors, TsF, play a major role in the communication between different suppressor cells. Characterization of polyclonal and monoclonal factors produced by Tsi, called TsFi, indicates that they both bind to tumor antigen and contain tumor-specific (idiotypic?) determinants.

[Pathogenesis and immunotherapy of insulin-dependent (type I) diabetes mellitus]

The association of insulin-dependent (type I) diabetes mellitus with HLA-DR3 and DR4 and with several epidemiological, virological, immunological, and clinical data suggests a heterogenous pathogenesis. the initial lesion in most cases is a virologically induced autoimmune process. It is only rarely that insulin-dependent diabetes results from a pure viral infection or as part of polyendocrine autoimmune deficiencies. The knowledge of the genetical risk factors and of disease-specific humoral and cellular immune deviations exhibits possibilities of successful intervention by means of immunotherapy.

Dissection of the Poly(Glu60Ala30Tyr10) (GAT)-specific T-cell repertoire in H-2Ik mice. II. The use of monoclonal antibodies to study the recognition of Ia antigens by GAT-reactive T-cell clones

Twenty-five allospecific monoclonal antibodies (mAb), produced in the A. TH. A.BY, or B10.S (7R) anti-A.TL combinations, were shown to recognize determinants organized in four spatially distinct polymorphic regions on the same I-Ak-encoded molecule(s). These reagents were used to assess the recognition of the class II major histocompatibility complex (MHC) determinants in a series of GAT-reactive A.TL T-cell clones exhibiting various restriction specificity or alloreactivity patterns. Of the proliferative responses of 13 cloned T cells, 12 responses were found to be inhibited similarly by the same set of mAbs.A hierarchy in the blocking effects of these reagents that could be correlated with the spatial organization of their determinants was observed. (i) All the mAbs defining the epitope region I (i.e., recognizing public Ia.1- or Ia.17-like determinants, presumably expressed on the A beta subunit) and some of those identifying new public determinants in the epitope region II profoundly inhibited these T-cell responses. (ii) Intermediate blocking was observed when mAbs recognizing public determinants in the epitope region III were used. (iii) Finally, among the mAbs that identified the epitope group IV, the Ia.19-specific mAb 39.J was inhibitory, whereas mAbs directed against private Ia.2-like determinants were not. By contrast, the GAT-specific proliferative response of the T-cell clone AT-20.1, which recognized its nominal antigen in an extensively cross-reactive MHC-restricted fashion, could only be inhibited by a subset of the mAbs recognizing epitopes in groups I and II, but not by those recognizing epitopes in groups III and IV. It was also shown that the same subset of I-Ak-and I-Au-reactive mAbs displayed similar blocking effects on the proliferation of two T-cell clones exhibiting dual specificity for I-Ak- and I-Au-restricting and/or I-Ak- and I-Au-alloactivating determinants. Finally, all the cloned T-cell responses examined were found to be inhibited by rat mAbs against the LFA.1 molecule or the murine equivalent of the human OKT4 differentiation antigen. These studies suggest that class II specific mAbs can impair proliferation of cloned T-cells by a mechanism(s) other than the masking of the T-cells' restriction determinants per se.

Leishmania donovani infection in heterozygous and recombinant H-2 haplotype mice

On a B10 (Lshs) genetic background the development of acquired T-cell-mediated immunity to Leishmania donovani infection in mice is under H-2-linked genetic control. Three phenotypic patterns of recovery were previously observed: "early cure" (H-2s, H-2r), "cure" (H-2b) and "noncure" (H-2d, H-2q, H-2f), with cure behaving as a recessive trait in H-2b/H-2d mice. In this study the long-term response to L. donovani is followed over 130 days of infection in eight recombinant haplotype strains and in six further heterozygous haplotype combinations. Noncure in B10.HTG mice, which carry d alleles for loci at the K end and b alleles for loci at the D end of H-2, confirms that H-2-linked genetic control of the acquired response to L. donovani infection is located in the K end. The complex pattern of dominance relationships observed in the additional heterozygous haplotypes studied, the variable phenotypic response of H-2k mice and of recombinant haplotype strains carrying IEk in common, and the differential early curing activity observed in heterozygotes involving the s but not the r early cure haplotype and in recombinant haplotype mice carrying s alleles to the left of IE suggest, however, that more than one subregion (IE and presumably IA) are involved. Results are interpreted in the light of immunoregulatory T-cell populations previously demonstrated in noncure, cure, and early cure strains.

Both DR and MT class II HLA molecules may restrict proliferative T-lymphocyte responses to antigen

Antigen-primed T-cell blasts may be separated from alloreactive T cells on Percoll gradients. By means of this method, HLA restriction of antigen-specific proliferative T-cell responses may be studied, using allogeneic antigen-presenting cells carrying foreign D/DR antigens. The reported data confirm that the D/DR molecules as such are major restriction elements in the T-cell response to herpes simplex virus (HSV) and purified protein derivative (PPD). However, evidence is presented that other Class II HLA molecules, the MT molecules, may also function as restriction elements for the HSV response.

Role of Ia antigen expression and secretory function of accessory cells in the induction of cytotoxic T lymphocyte responses against herpes simplex virus

Splenocytes from mice which have been primed in vivo with herpes simplex virus type 1 (HSV-1) can be restimulated in vitro with infectious or UV-inactivated HSV-1 to generate HSV-specific, H-2-restricted cytotoxic T lymphocytes (CTL). HSV-primed splenocytes which have been depleted of adherent cells by sequential incubation on plastic, nylon wool, and Sephadex G-10 are not able to respond with a CTL response when restimulated in vitro. A variety of Ia-positive and Ia-negative (Ia(+) and Ia(-)) cell populations were assessed for their ability to supply accessory cell functions to spleen cells which had been exhaustively depleted of adherent cells, as measured by the restoration of a CTL response to HSV-1. Of these, only those populations which included Ia(+) cells were capable of providing accessory cell function. The ineffective populations were devoid of Ia antigens, except for B lymphocytes, which are Ia(+) and still incapable of serving as accessory cells. Splenic adherent cells and resident peritoneal cells were both proficient at restoring anti-HSV CTL responses, although splenic adherent cells were clearly superior at limiting cell numbers. Neither population was capable of accessory cell activity, however, if it was pretreated with anti-Ia antiserum plus complement or if anti-Ia serum was present during induction. Peritoneal cells lose virtually all of their membrane-associated Ia antigen after a brief period of in vitro culture (24 to 48 h). Cultured peritoneal cells, as well as P388D(1) cells (normally Ia(-)), can be induced to express Ia antigens within 48 h if they are cultured with concanavalin A-stimulated spleen cell supernatants. Ia(+) P388D(1) cells without the extraneous macrophage factor are not able to restore CTL responsiveness to HSV-1 in vitro, whereas Ia(+) cultured macrophages are fully competent accessory cells. When Ia(+) P388D(1) cells were supplemented with the macrophage-derived soluble factor interleukin 1, they displayed a modest, but significant, capacity to restore secondary anti-HSV CTL responses. In addition, glutaraldehyde-fixed, HSV-1-infected Ia(+) peritoneal cells, which could not restore the CTL response alone, were capable of providing accessory cell function if extraneous interleukin 1 was provided. In contrast, Ia(-) cultured peritoneal cells, Ia(-) P388D(1) cells, and various other Ia(-) cell lines were unable to participate in the generation of CTL even in the presence of interleukin 1. The adherent cell population would therefore appear to be making at least two essential contributions to the process of CTL development, namely, the secretion of interleukin 1 and the presentation of antigen in the context of membrane-associated Ia antigen.

Conversion of immunity to suppression by in vivo administration of I-A subregion-specific antibodies

The in vivo administration of antibodies specific for gene products of the I-A subregion represents an immunologically specific approach to the manipulation of Ly-1+ T cell responses to antigen. This has been demonstrated previously by the capacity of anti-I-A antibody treatment to abrogate T cell-mediated delayed-type hypersensitivity (DTH) responses to syngeneic tumor antigen, hapten, and non-H-2 histocompatibility antigens. Evidence obtained in these studies suggested that the primary action of antibody was related to its ability to interfere with macrophage-T cell interactions during antigen presentation, consistent with the demonstration that similar antibodies inhibit T cell binding to antigen-pulsed macrophages in vitro. Results presented in this report provide evidence for an additional consequence of in vivo antibody administration that may be secondary to any direct effects on I-A-restricted antigen presentation. Thus, animals treated with I-A subregion-specific antibodies also develop a population of antigen-specific suppressor T cells (Ts) capable of inhibiting recipient Ly-1+ T cell responses to tumor antigen. The induction of suppression appeared to be an essential component of the total biological activity of these antibodies, because elimination of Ts precursors by cyclophosphamide also abrogated the antibody-mediated inhibition of DTH responsiveness. These results are discussed with respect to the possible mechanisms of Ts activation by anti-I-A antibody administration, and the general applicability of this approach as a means of clinical immunotherapy to limit inappropriate T cell responses in human disease.

Biochemical characterization of a second family of human Ia molecules, HLA-DS, equivalent to murine I-A subregion molecules

In mice, two families of structurally distinct Ia molecules, one designated I-A and the other I-E, have been identified and characterized. The HLA-DR molecules represent one family of human Ia molecules equivalent to the murine I-E molecules on the basis of amino acid sequence homology. We describe the isolation and biochemical characterization of a second family of human Ia molecules, designated HLA-DS for second D-region locus, equivalent to the murine I-A molecules. The human HLA-DS molecules consist of two polypeptide chains, DS alpha (37,000 mol wt) and DS beta (29,000 mol wt), with 73% amino acid sequence identity to the murine I-A molecules. Furthermore, the HLA-DS molecules are closely linked genetically to HLA-DR molecules, a situation analogous to that observed in mice. The similarity in molecular weights of the DR and DS molecules might explain why others have failed to identify the latter in man.

Role of the H-2 complex in induction of T helper cells in vivo. III. Contribution of the I-E subregion to restriction sites recognized by I-A/E-restricted T cells

Previous studies on negative selection of T cells to sheep erythrocytes in irradiated mice showed that CBA (I-Ak,I-Ek) (kk) T cells comprise two subgroups of cells restricted by I-A (A alpha-A beta) and I-A/E (E alpha-E beta) molecules. Selection of the I-A/E-restricted by I-A (A alpha-A beta) and I-A/E (E alpha-E beta) molecules. Selection of the I-A/E-restricted subset requires that the donor T cells and the selection host share both I-A (E beta) and I-E (E alpha) gene products; only the I-A-restricted cells undergo selection in B10.A(4R) (kb) mice. This paper demonstrates that negative selection of the I-A/E-restricted subgroup of CBA T cells can occur in F1 hybrids between B10.A(4R) and various Ia.7+ (E alpha+) I-E-incompatible strains; selection does not occur in hybrids between B10.A(4R) and Ia.7- (E alpha-) strains. These data suggest that, despite the fact that E alpha chains display detectable structural allelic variations, these chains are functionally nonpolymorphic. This conclusion applies to E alpha k,d,p,r,j chains. With F1 hybrids between B10.A(4R) and another Ia.7+ strain, B10.PL (H-2u), in contrast, only intermediate selection is observed. This finding is consistent with recent evidence that cell surface expression of E alpha-u-E beta dimers displays strong cis preference. In contrast to E alpha+ CBA T cells, E alpha- B10.A(4R) (kb) T cells undergo complete negative selection in hosts matched only in the I-A (and H-2K) subregion, i.e., B10.BR (kk) mice; no selection occurs in B10 (bb) mice. These data imply that Ia-restricted T cells in E alpha- strains are probably restricted solely by I-A molecules.

Immune response gene function correlates with the expression of an Ia antigen. I. Preferential association of certain Ae and E alpha chains results in a quantitative deficiency in expression of an Ae:E alpha complex

These studies were stimulated by the observation, reported in the accompanying paper (19), that IEu failed to interact with I-Ak or I-As in F1 mice to allow a response to the antigen, pigeon cytochrome c, unlike I-E subregions derived from other Ia.7+ haplotypes. Serological and biochemical analyses were performed to determine whether or not cells from these F1 mice express the Ak,se:E alpha complexes that should function as restriction elements for T cell recognition of pigeon cytochrome c on antigen-presenting cells. Using the Y-17 monoclonal antibody, which recognizes the combinatorial or conformational determinant Ia.m44 on certain Ae:E alpha complexes, we were able to distinguish between Aue:Eu alpha and Ab,k,se:Eu alpha complexes on cell surfaces. Although complement-dependent microcytotoxicity with Y-17 failed to detect Ab,k,se:Eu alpha complexes on cells from appropriate F1 mice, these molecules were detected by both quantitative absorption and quantitative immunofluorescence studies. However, Ab,k,se:Eu alpha complexes were found to be present at levels only one-seventh to one-eighth the levels expressed by homozygous I-Ab, I-Ek; I-Ak, I-Ek; and I-As, I-Ek cells. The results of two-dimensional polyacrylamide gel electrophoresis analyses suggest that the low levels of expression of Ab,k,se:Eu alpha complexes are a consequence of the preferential association of Aue and Eu alpha chains with each other in the F1 cells. As will be shown in the following paper (19), the quantitative deficiency in the expression of Ake:Eu alpha and Ase:Eu alpha complexes results in a corresponding defect in antigen-presenting cell function, thus providing strong evidence that Ia antigens represent products of Ir genes.

Immune response gene function correlates with the expression of an Ia antigen. II. A quantitative deficiency in Ae:E alpha complex expression causes a corresponding defect in antigen-presenting cell function

A series of experiments were performed to explore the role of complementing major histocompatability complex (MHC)-linked immune response Ir genes in the murine T cell proliferative response to the globular protein antigen pigeon cytochrome c. The functional equivalence of I-E-subregion-encoded, structurally homologous E(a) chains from different haplotypes bearing the serologic specificity Ia.7 was demonstrated by the complementation for high responsiveness to pigeon cytochrome c of F(1) hybrids between low responder B 10.A(4R) (I-A (k)) or B 10.S (I-A(8)) mice and four low responder E(a)- bearing haplotypes. Moreover, this Ir gene function correlated directly with both the ability of antigen-pulsed spleen cells from these same F(1) strains to stimulate pigeon cytochrome c-primed T cells from B10.A or B10.S(9R) mice, and with the cell surface expression of the two-chain Ia antigenic complex, A(e):E(a), bearing the conformational or combinatorial determinant recognized by the monoclonal anti-Ia antibody, Y-17. The B 10.PL strain (H-2(u)), which expresses an Ia.7-positive I-E- subregion-encoded E(a) chain, failed to complement with B10.A(4R) or B10.S mice in the response to pigeon cytochrome c. However, (B10.A(4R) x B10.PL)F(1) and (B10.S x B10.PL)F(1) mice do express A(k)(e):E(u)(a) and A(8)(e):E(u)(a) on their cell surface, although in reduced amounts relative to A(k,s)(e):E(k,d,p,r)(a) complexes found in corresponding F(1) strains. This quantitative difference in Ia antigen expression correlated with a difference in the ability to present pigeon cytochrome c to B 10.A and B 10.S(9R) long-term T cell lines. Thus, (B10.A(4R) x B10.PL)F(1) spleen cells required a 10-fold higher antigen dose to induce the same stimulation as (B10.A(4R) x B10.D2)F(1) spleen cells. In addition, the monoclonal antibody, Y-17, which reacts with A(e):E(a) molecules of several strains, had a greater inhibitory effect on the proliferative response to pigeon cytochrome c of B10.A T cells in the presence of (B10.A(4R) X B10.PL)F(1) spleen cells than in the presence of (B10.A(4R) X B10.D2)F(1) spleen cells. These functional data, in concert with the biochemical and serological data in the accompanying report, are consistent with the molecular model for Ir gene complementation in which appropriate two-chain Ia molecules function at the antigen-presenting cell (APC) surface as restriction elements. Moreover, they clearly demonstrate that the magnitude of the T cell proliferative response is a function of both the concentration of nominal antigen and of the amount of Ia antigen expressed on the APC. Finally, the direct correlation of a quantitative deficiency in cell surface expression of an Ia antigen with a corresponding relative defect in antigen-presenting function provides strong independent evidence that the I-region-encoded Ia antigens are the products of the MHC-linked Ir genes.

Analysis of unexpected inhibitions of T lymphocyte proliferation to soluble antigen, alloantigen and mitogen by unfragmented anti-I-Ak or anti-I-E/Ck monoclonal antibodies

We investigated the capacity of anti-I-Ak and anti-I-E/Ck monoclonal antibodies (m.Ab.) to inhibit T lymphocyte proliferative responses to soluble antigen (Keyhole limpet hemocyanin), alloantigens (H-2 or non-H-2 related) and a mitogen (Concanavalin A). Surprisingly, specific inhibition was observed in all circumstances, and with both anti-I-Ak and anti-I-E/Ck m.Ab., whether the responses tested were I restricted in cell mixing experiments or not. The significance of the inhibition by anti-Ia m.Ab. of non-Ia-restricted responses is still not completely understood. These results, however, strongly suggest that in vitro inhibition by anti-Ia antibodies of T cell proliferative responses does not necessarily indicate I restriction of the presentation to T lymphocytes of the corresponding antigen.

Inhibition of murine T cell-mediated cytolysis and T cell proliferation by a rat monoclonal antibody immunoprecipitating two lymphoid cell surface polypeptides of 94 000 and 180 000 molecular weight

The monoclonal antibody methodology was use to identify membrane structures involved in T cell functions. To optimize chances to produce and detect relevant antibodies, a xenogeneic sensitization protocol was utilized and hybridoma supernatants were screened, on functional rather than structural grounds, for their ability to inhibit a given function. The test function was T cell-mediated cytolysis. Mouse cytolytic anti-allogeneic cell populations were used to sensitize a rat, the spleen cells of which were fused to produce hybridomas; the supernatants of the latter were screened for their ability to inhibit mouse T cell-mediated cytolysis in vitro. Several inhibitory antibodies were obtained, one of which, H35-89.9 monoclonal antibody, was studied in more detail. It inhibited specific and concanavalin A (Con A)-mediated cytolysis by T cells, by acting on the effector cells. It reversibly inhibited soluble antigen-, alloantigen and Con A-induced T cell proliferation (but not LPS-induced B cell proliferation), after the production of interleukin 2, by acting on the responder cells. It also had a desagglutinating effect on Con A and LPS blasts and on EL4 cells. In immunoprecipitated from thymocyte membrane preparations two structures of 94 000 and 180 000 apparent molecular weight, and recognized cell surface determinants on both T and B lymphocytes. Our findings suggest that several antibodies directed against distinct effector cell membrane structures inhibit cytolysis. The case of H35-89.9 monoclonal antibody, which exerts multiple functional effects and immunoprecipitates two membrane polypeptides, raises the problem of the various possible relationships between these structures and functions.