Idiotype-like determinants on human T lymphocytes alloactivated in mixed lymphocyte culture.

T cells alloactivated in 5-d MLC with an HLA-DR-different stimulator acquire the capacity of stimulating the autologous mixed lymphocyte response (AMLR). We have demonstrated that activation of AMLR by allosensitized T cells is determined by the expression of the idiotype receptor for the stimulating HLA-DR alloantigen. This has been shown in experiments in which purified, OKT-3-positive T cell suspensions were first primed for 9 d with AMLR-activated T lymphoblasts, then tested in secondary AMLR with autologous lymphoblasts sensitized to various HLA-DR alloantigens. Accelerated memory responses were induced only by autologous lymphoblasts that had been sensitized against the same HLA-DR specificity as the primary AMLR stimulators. This response was not inhibited by a mouse monoclonal antibody recognizing Ia-like determinants, and was not triggered by human allogeneic resting peripheral blood lymphocytes. Thus, recognition of alloactivated T lymphoblasts in secondary AMLR seems to be specific for the idiotype-like determinants expressed by the autologous stimulators.

Differentiation-stage specific self-peptides bound by major histocompatibility complex class I molecules.

We have tested the hypothesis that phenotypic changes of development are accompanied by expression of differentiation-stage specific peptides bound to major histocompatibility complex (MHC) class I molecules. The U937 cell line, when cultured in the presence of phorbol myristate acetate (PMA), undergoes differentiation from monoblasts to macrophage-like cells. The high-performance liquid chromatography profile of peptides eluted from purified human histocompatibility leukocyte antigen class I molecules expressed by U937 treated with PMA differs from that obtained from control, untreated U937 cells. Chemical sequencing of eluted peptides identified a peptide derived from cytomegalovirus in both treated and untreated cells. PMA-treated, but not untreated cells, displayed an additional peptide derived from interleukin 1 beta. Hence, differentiation-induction of U937 is accompanied by the presentation of at least one differentiation-stage specific peptide. Our results indicate that, similar to viral infection, cellular development and transformation is accompanied by the de novo synthesis of proteins which are processed and presented on MHC class I molecules.

Rearrangement and expression of the alpha, beta, and gamma chain T cell receptor genes in human thymic leukemia cells and functional T cells.

Using cDNA and genomic probes representing the alpha, beta, and gamma chain of the human T cell receptor genes, we have examined the structure and expression of these genes in 14 human leukemic T cell lines, representing different stages of thymic differentiation, and 15 functional human T cell clones. Rearrangement of the gamma and beta chain genes was found in all of the functional T cell clones and all but one (P30/OKUBO) thymic leukemia cell line; all of the lines that had rearrangement of the beta chain expressed beta mRNA. Expression of the alpha chain was found in all of the functional T cell clones examined, while rearrangement of the alpha chain gene, using currently available probes to the J region, could be shown in 10 of 13 functional clones. In contrast, expression of the alpha chain was found in 6 of 10 leukemic T cell lines, while rearrangement was found in six of these nine cell lines. Of the 14 leukemic cell lines studied for rearrangement of the alpha chain, rearrangement was found in six cases. The data obtained with the cell lines are consistent with an ordered rearrangement and expression of the gamma, beta, and alpha chains of the T cell antigen receptor (TcR) genes. The leukemic cell lines used in the present study have previously been characterized with regard to cell surface antigens and intracellular enzymes. Based on those results a scheme of thymic development was proposed. The developmental stages identified by those studies are not in complete agreement with stages of T cell development, as determined in the present study using molecular probes.

T cell recognition of self-human histocompatibility leukocyte antigens (HLA)-DR peptides in context of syngeneic HLA-DR molecules.

It has been suggested that self major histocompatibility complex (MHC) peptides bound to self MHC molecules may be involved in the intrathymic induction of self tolerance. We studied the antigenicity of synthetic peptides derived from the first domain of DR beta 1*0101 chain in a DR beta 1*0101 responder. We found that a peptide corresponding to residues 21-42 of the beta chain could elicit the proliferation of autoreactive T cells. A T cell line (TCL-SUN) and 7 of 9 T cell clones (TCC) derived from TCL-SUN specifically recognized peptide 21-42 in the presence of APCs carrying the DR beta 1*0101 allele. DR beta 1*0101 positive APCs stimulated the TCCs in the absence of peptide, although the magnitude of the response was much lower than in cultures with peptide. This suggests that self DR1 molecules are continuously processed into peptides that are presented by the DR1 molecules on the surface of the cells. The data indicate that some T cells whose TCR binds to self MHC peptides presented by self MHC molecules are not deleted, although their ligand is continuously present. TCCs specific for peptide 21-42 presented in the context of DR1 were also stimulated by cells heterozygous for DR beta 1*0301 and 1601, indicating that some DR peptide-specific autoreactive T cells participate in alloreactivity.

Contribution of direct and indirect recognition pathways to T cell alloreactivity.

T cells from an HLA-DR11/DR12 responder were stimulated in mixed lymphocyte culture with cells carrying the DR1 antigen. After priming, T cells proliferated in response to both DR1-positive-stimulating cells and a peptide derived from a polymorphic region of the HLA-DR beta 1*0101 chain presented by responder's antigen-presenting cells (APC). The dominant epitope recognized by the primed T cells corresponded to residue 21-42 and was presented by the responder's HLA-DR12 antigen. The DR1 peptide-reactive T cells express T cell receptor V beta 3. The results demonstrate that allopeptides derived from the processing and presentation of donor major histocompatibility complex molecules by host-derived APC trigger alloreactivity. The frequency of T cells engaged in the indirect pathway of allorecognition is about 100-fold lower than that of T cells participating in the direct recognition of native HLA-DR antigen. However, indirect allorecognition may play an important role in chronic allograft rejection, a phenomenon that is mediated by the activation of T helper cells and of alloantibody-producing B cells.

The HLA system in the families of patients with juvenile diabetes mellitus.

The HLA and Bf genotypes were determined in 10 families with one or more children with JDM. A statistically significant association was found between HLA-D-identity and the chance to present JDM within a sibship. No such association was detectable with the SD antigens. A highly significant increase in the frequency of intra-HLA recombination was also found in these families.

Inhibition of cellular mediated immunity in marihuana smokers.

The cellular mediated immunity of 51 young chronic marihuana smokers. as evaluated by the lyomphocyte response in vitro to allogeneic cells and to phytohemagglutinin, was significantly decreased and similar to that of patients in whom impairment of T (thymus derived) cell immunity is known to occur. This inhibition of blastogenesis might be related to an impairment of DNA synthesis.

Sensitivity, specificity and clinical relevance of different cross-matching assays in deceased-donor renal transplantation.

To assess the significance of antibodies detected by complement-dependent cytotoxicity (CDC), solid phase (SPA) and flow cytometry (FC) assays we compared their predictive value in 354 consecutive cases of deceased-donor kidney transplantation. Pre-transplantation screening of anti-HLA class I and class II antibodies was performed by CDC and SPA. The direct crossmatch between recipients' sera and donors' T and B cells was performed by CDC followed by FC and SPA ("virtual cross-match"). The past history of antibodies displayed by the recipient was not considered a contraindication for transplantation even when it showed DSA. A side-by-side comparison of the correlation between graft loss, history of DSA and cross-match results indicated that sensitivity was 5%, 16% and 17% while specificity was 99%, 93% and 86% in CDC, SPA, FC crossmatches respectively. There was no significant difference between the 3 year survival of primary and secondary kidney allografts. We conclude that screening and cross-matching the sera by CDC provides reliable results and optimizes the patient's chances to receive a transplant. SPA and FC, however, are of great importance for identifying patients which require close monitoring by biopsy and serology for early diagnosis and treatment of acute antibody mediated rejection (AAMR).

Amplification of T cell blastogenic responses in healthy individuals and patients with acquired immunodeficiency syndrome.

Human immunodeficiency virus (HIV) infection is associated with a profound impairment of T cell function. Hence, enhancement of T cell reactivity to viral and bacterial antigens is important in the treatment of patients with AIDS. To develop tools for amplifying T cell reactivity, we have immunized mice with human helper T cell clones and selected monoclonal antibodies (MAbs) that enhance in vitro blastogenic responses. MAb NDA5, which recognizes the leukocyte common antigen CD45, amplifies human T cell responses to mitogens and soluble antigens including HIV-1 glycoprotein (gp)-120 and peptides derived from the HIV-1 gp-120 sequence. In the presence of MAb NDA5, peripheral blood mononuclear cells (PBMC) from healthy, HIV-1-seronegative individual displayed augmented blastogenic responses to HIV-1 gp-120 and to HIV-1 gp-120 synthetic peptides. In vitro memory responses to various vaccines and to alloantigens were also enhanced in cultures with MAb. Similarly, the response of PBMC from AIDS patients to pokeweed mitogen, HIV-1 gp-120, and tetanus toxoid was enhanced with MAb NDA5. The finding that the in vitro immune response of patients with AIDS can be amplified with MAb NDA5, suggests that the in vivo immune response of immunodeficient individuals can also be enhanced.

Persistent allopeptide reactivity and epitope spreading in chronic rejection of organ allografts.

The role of the indirect allorecognition pathway in acute allograft rejection has been documented both in organ recipients and in experimental models. However, it is unknown whether self-restricted recognition of donor alloantigens also contributes to chronic allograft rejection. The aim of this study was to determine the relationship between allopeptide reactivity, epitope spreading, and chronic rejection. Using synthetic peptides corresponding to the hypervariable region of 32 HLA-DR alleles, we have followed the specificity of self-restricted T cell alloresponses to the donor in a population of 34 heart allograft recipients. T cells from sequential samples of blood collected from the patients up to 36 mo after transplantation were studied in limiting dilution analysis for allopeptide reactivity. The incidence of coronary artery vasculopathy (CAV) was significantly higher in patients who displayed persistent alloreactivity late after transplantation than in patients who showed no alloreactivity after the first 6 mo after transplantation. Both intra- and intermolecular spreading of epitopes was observed with an increased frequency in patients developing CAV in less than 2 yr, compared with patients without CAV; this suggests that diversification of the immune response against the graft contributes to chronic rejection. These data provide a strategy for identifying patients at risk of developing CAV and a rationale for therapeutic intervention aimed to prevent the progression of the rejection process.

Indirect recognition of donor HLA-DR peptides in organ allograft rejection.

To determine whether indirect allorecognition is involved in heart allograft rejection T cells obtained from peripheral blood and graft biopsy tissues were expanded in the presence of IL-2 and tested in limiting dilution analysis (LDA) for reactivity to synthetic peptides corresponding to the hypervariable regions of the mismatched HLA-DR antigen(s) of the donor. Serial studies of 32 patients showed that T cell reactivity to donor allopeptides was strongly associated with episodes of acute rejection. The frequency of allopeptide reactive T cells was 10-50-fold higher in the graft than in the periphery indicating that T cells activated via the indirect allorecognition pathway participate actively in acute allograft rejection. In recipients carrying a graft differing by two HLA-DR alleles the response appeared to target only one of the mismatched antigens of the donor. Indirect allorecognition was restricted by a single HLA-DR antigen of the host and directed against one immunodominant peptide of donor HLA-DR protein. However, intermolecular spreading was demonstrated in patients with multiple rejection episodes by showing that they develop allopeptide reactivity against the second HLA-DR antigen. These data imply that early treatment to suppress T cell responses through the indirect pathway of allorecognition, such as tolerance induction to the dominant donor determinant, may be required to prevent amplification and perpetuation of the rejection process.

Anti-CD25 treatment and FOXP3-positive regulatory T cells in heart transplantation.

The interleukin-2 receptor alpha chain (IL-2Ra, CD25) plays a major part in shaping the dynamics of T cell populations following immune activation, due to its role in T cell proliferation and survival. Strategies to blunt the effector responses in transplantation have been developed by devising pharmaceutical agents to block the IL-2 pathways. However, such strategies could adversely affect the CD25(+)FOXP3(+)T regulatory (T reg) populations which also rely on intereukin-2 signaling for survival. The present study shows that a cohort of heart allograft recipients treated with Daclizumab (a humanized anti-CD25 antibody) display FOXP3 expression patterns consistent with functional T regulatory cell populations. High levels of FOXP3 were observed to correlate with lower incidence of and recovery from acute rejection, as well as lower levels of anti-donor HLA antibody production. Therefore, T reg populations appear fully functional in patients treated with Daclizumab, even when 5 doses were administered. By comparison, patients treated with fewer doses or no Daclizumab had a higher incidence of acute rejection, antibody production and graft failure. Therefore, our data indicates that Daclizumab treatment does not interfere with the generation of regulatory T cells and has a beneficial effect on heart allograft survival.

Tissue-specific self-peptides bound by major histocompatibility complex class I molecules of a human pancreatic beta-cell line.

The process of beta-cell destruction in IDDM is mediated, in part, by CD8+ T-cells. Structural characterization of HLA-I-bound self-peptides presented by the human beta-cell line HP-62 was performed to identify possible tissue-specific autoantigens in the context of CD8+ T-cell/HLA-I interactions. The sequences of the beta-cell line HLA-I-bound peptides were compared with sequence databases. Six of the obtained sequences showed homology to known precursor proteins, three of which--GLUT2 receptor, phosphatidylinositol-glycan-specific phospholipase D, and 5-hydroxytryptamine-1F receptor--have a limited, tissue-specific expression. These HLA-bound self-peptides may be part of a pool of autoantigens recognized by beta-cell reactive cytotoxic T-cells.

No excess of DR*3/4 in Ashkenazi Jewish or Hispanic IDDM patients.

The gene frequencies, haplotype relative risks, and zygotic assortments of HLA-DR in three ethnically defined samples of insulin-dependent diabetes mellitus (IDDM) patients were determined in a prospective family study. Although DR3 and DR4 were positively associated with IDDM in the probands of 123 northern European, 94 Ashkenazi Jewish, and 49 New York Hispanic families, significant excess of DR*3/4 heterozygotes was observed only among the probands from families of northern European ancestry. There was also a significant decrease in the frequency of Bw62,DR4 haplotypes derived by northern European patients from their mothers compared with their fathers. This difference, together with data reported in the literature, suggests that the expressivity of the susceptible genotype(s) in IDDM patients may be modified by protective maternal effects associated with Bw62,DR4 and probably other DR4 haplotypes. Samples of IDDM patients from populations with high frequencies of these modifiers should have different DR-gene frequencies contributed by fathers and mothers, capable of accounting for the observed Hardy-Weinberg disequilibrium. We postulate that, because the mechanism of action of these modifiers is distinct from that of the susceptibility gene, the difference must be considered in devising strategies for elucidation of the mode of inheritance of the disease and for understanding the molecular nature of the susceptibility.

Wild-type p53 epitope naturally processed and presented by an HLA-B haplotype on human breast carcinoma cells.

To broaden the clinical applicability of peptide-based immunotherapy in breast cancer, there is a need to identify further tumor-associated peptide epitopes that are specific for HLA alleles, in addition to HLA-A2. The HLA-B44 haplotype is one of the most common HLA-B haplotypes, occurring in 10-20% of the population. We performed the structural characterization of HLA class I-bound self-peptides presented by a human breast cancer cell line with a HLA-A68, A32, B40, B44 haplotype, to identify potential tumor-specific antigens. Of 13 sequenced peptides, 1 peptide had the HLA-A68 peptide binding motif and 12 peptides had the HLA-B40, B44 peptide binding motif. One of the latter peptides, FEVRVCACPG, shared 100% homology to residues 270-279 of wild-type P53 protein. Our study, thus, provides direct evidence for the natural processing and presentation of p53 epitope 270-279 by HLA-B40, B44-bearing human breast tumor cells. Epitopes spanning this region of P53 may have potential use for immunotherapy in patients expressing HLA-A2 and -B44 supertypes.

Infectious tolerance mediated by CD8+ T-suppresor cells after UV-B-irradiated donor-specific transfusion and rat heart transplantation.

AIMS: CD8+CD28- human T-suppressor cells (Ts), which can be generated in vitro, act directly on APC rendering them tolerogenic to unprimed and primed CD4+ T cells. The aim of this study was to investigate the possibility that CD8+ T cells mediate the induction of tolerance in a heart transplantation model in rodents. MATERIALS AND METHODS: Blood from Lewis rats was UV-B-irradiated and transfused into ACI recipients on days -21, -14, and -7 before heart allograft transplantation on day 0. CD4(+) and CD8(+) T cells were positively selected from ACI rats, which had tolerated Lewis heart allografts for more than 100 days and were adoptively transferred to naive ACI rats pretreated (day -1) with gamma irradiation. These ACI rats underwent transplantation with Lewis hearts 24 hours after adoptive transfer of putative T-suppressor cells. RESULTS: Adoptive transfer of CD8(+) T cells from tolerant ACI to naive ACI rats significantly prolonged Lewis heart mean allograft survival time (MST +/- SD) to 69 +/- 13 days as compared with 15 +/- 1 and 14 +/- 1 days in animals adoptively transferred with CD4+ T cells or untreated controls, respectively (P < .001). Similarly, adoptive transfer of CD8(+) T cells from secondary ACI recipients to naive syngeneic animals also significantly prolonged survival of heart allografts to MST +/- SD of 72 +/- 4 for CD8(+) and 15 +/- 4 days for CD4(+) T cells (P < .001). CONCLUSIONS: These data demonstrate that allogeneic tolerance induced in ACI recipients by treatment with UV-B-irradiated blood from Lewis donors is mediated by CD8+ T-suppressor cells.

Complexes of soluble HLA antigens and anti-HLA autoantibodies in human sera: possible role in maintenance of self-tolerance.

The MHC plays an essential role in regulating the process of self-nonself discrimination. T cells recognize nonself antigens only in the context of self-MHC gene products. It is not clear, however, whether B cells are also endowed with immune receptors for self-MHC antigens. We have explored the existence of antibodies against self-MHC antigens (HLA) in the human by analyzing the specificity of anti-HLA antibodies developed by a population of 727 dialysis patients who had been monitored monthly over a period of 3-78 months. Anti-HLA autoantibodies were identified by serum screening in 119 patients. Twenty-five of these 119 patients had not been exposed to alloantigens before, indicating that the production of anti-HLA autoantibodies is not necessarily stimulated by allogeneic HLA antigens. Cross-matching of sera with autologous lymphocytes, confirmed the autoreactive nature of these anti-HLA antibodies which were of IgM or of IgG isotype in approximately equal numbers of patients. The fine specificities of anti-HLA autoantibodies was ascertained in studies which showed that antibodies can be adsorbed, and the eluted, from the membranes of target cells carrying then relevant HLA antigen. Since the antibodies characterized in our studies may be functionally active in vivo we examined the possibility that their level is controlled by anti-idiotypic antibodies or by soluble HLA antigens. We found that the titer of anti-HLA autoantibodies increased significantly if soluble HLA antigens were depleted from the serum. Our data suggest that circulating HLA antigens form immune complexes with anti-HLA autoantibodies and contribute to the maintenance of self-tolerance by inhibiting antibody binding to membrane HLA antigens. The finding that the immune repertoire includes B cells with receptors for self-MHC opens new perspectives for the study of network perturbations in autoimmune diseases.

Major histocompatibility complex-restricted recognition of autologous chronic lymphocytic leukemia by tumor-specific T cells.

From the peripheral blood of a patient with chronic lymphocytic leukemia (CLL) we generated a T-cell line and clones which recognized autologous CLL. The line comprised T-cell clones which responded to the CLL as well as to autologous Epstein-Barr virus (EBV)-transformed B cells in an HLA-DR-restricted fashion. In addition, the line comprised clones which were CLL-specific and showed no reactivity against EBV-transformed B cells and against autologous peripheral blood mononuclear cells obtained during remission. The proliferative response of the CLL-specific T-cell clone was inhibited by monoclonal antibodies to HLA-DR11, the major histocompatibility complex (MHC)-restrictive element. These results indicate that the MHC class-II molecule of CLL binds a tumor-specific peptide which is recognized by autologous T cells in an MHC class-II-restricted fashion. Such a peptide may serve as a target for immunotherapy.

Anti-idiotypic antibodies specific for HLA in heart and kidney allograft recipients.

Chronic rejection is the major threat to both heart and renal allograft survival. We have explored the possibility that some patients with anti-donor HLA antibodies (Ab1) develop specific anti-idiotypic antibodies (Ab2) which suppress the production of Ab1, and subsequently, the progression of chronic rejection. Analysis of Ab2 in sera obtained from Ab1 producers showed that 22% of heart and 18% of kidney recipients produced Ab2. The 4- and 5-year actuarial graft survivals in Ab2 producers were 100% and 83%, respectively, compared to 57% in patients who formed Ab1 but not Ab2 (p < 0.004). Patients carrying the DR2 alleles, DRB1*1501, *1502 or *1601 were at a lower risk of producing anti-donor HLA antibodies.

HLA typing and Guillain-Barré syndrome.

In an effort to determine if there might be an association between Guillain-Barré syndrome and specific antigens of the HLA system, 18 patients with Guillain-Barré syndrome were typed for HLA-A, B, and D antigens. No statistically significant relationship was established by this study.