T-cell clones with similar antigen specificity may be restricted by DR, MT(DC), or SB class II HLA molecules

Duplicated DQ haplotypes increase the complexity of restriction element usage in cattle

The MHC of cattle encodes two distinct isotypes of class II molecules, DR and DQ. Unlike humans, cattle lack the DP locus and about half the common haplotypes express duplicated DQ genes. The number and frequency of DQA and DQB alleles means that most cattle are heterozygous. If inter- and/or intrahaplotype pairing of DQA and DQB molecules occurs, cattle carrying DQ-duplicated haplotypes may express more restriction elements than would be predicted by the number of expressed alleles. We are investigating whether duplicated haplotypes cause differences in immune response, particularly in terms of generating protective immunity. We have analyzed the Ag-presenting function of DQ molecules in two heterozygous animals, one of which carries a duplicated haplotype. We compared the class II isotype specificity of T cell clones recognizing a putative vaccinal peptide from foot-and-mouth disease virus (FMDV15). We show for the first time that bovine T cells can recognize Ag in the context of DQ molecules. We also present evidence that interhaplotype pairings of DQA and DQB molecules form functional restriction elements. Both animals showed distinct biases to usage of particular restriction elements. Mainly DQ-restricted clones were derived from the animal with duplicated DQ genes, whereas the majority of clones from the animal with a single DQ gene pair were DR restricted. Furthermore, haplotype bias was observed with both animals. These experiments show that understanding of class II chain pairing in addition to knowledge of the genotype may be important in vaccine design where effective epitope selection is essential.

The progression of renal diseases: on the pathogenesis of renal interstitial fibrosis

Renal interstitial fibrosis (RIF) frequently occurs in inflammatory and non-inflammatory kidney diseases and is associated with a decline in renal excretory function. Fibroblasts which occupy the renal interstitium are involved mainly in the formation of RIF not only by the production of extracellular matrix, but also by regulatory processes. They respond to a variety of cytokines released by different cell types. To investigate mechanisms leading to RIF, immunohistochemical analysis and cell cultures of renal biopsies in various renal diseases have been performed. T lymphocytes are the major cells infiltrating the renal interstitium, and their number correlates with the impairment of renal function. In most forms of glomerulonephritis accompanied by interstitial inflammation, an abnormal expression of HLA-DQ/-DP molecules, frequently associated with an aberrant expression of the intercellular adhesion molecule 1 (ICAM-1), was observed on proximal tubular epithelial cells, indicating that these cells may play a role in antigen presentation. The cell biological experiments revealed the presence of the three mitotic fibroblast types (MFI-MFIII) and the three postmitotic types (PMFIV-PMFVI) in the cell culture. The number of fibroblasts in primary and passage-1 culture was increased seven-fold in cultures derived from kidneys with RIF (FKIF cells) in comparison to normal kidneys (NKF cells). FKIF cells show hyperproliferative growth and synthesize an increased amount of total collagen, especially types III and V. These cells express a protein, named "FIBROSIN", which seems to be specific for FKIF cells. Further extended cell biological analyses are currently being performed to investigate interactions of tubular cells, lymphocytes, macrophages, and fibroblasts in order to shed more light on the pathomechanisms involved in fibrogenesis leading to renal interstitial fibrosis.

What is the basis for HLA-DQ associations with autoimmune disease?

The finding that diseases such as type I diabetes, coeliac disease and multiple sclerosis are HLA-DQ associated is not easily explained by a simple hypothesis of DQ-restricted, autoreactive T cells, considering the generally marginal role of DQ in restricting responses. Consequently, there have been various attempts to find a differential role for DQ, from presentation of special antigens to preferential stimulation of suppressor cells. Here, Daniel Altmann and colleagues critically assess these proposals and put forward the alternative hypothesis that the effect of DQ on disease susceptibility may result from a special role in shaping the T-cell receptor repertoire.

Decreased expression of class II major histocompatibility complex (MHC) molecules on monocytes is found in open-heart surgery related immunosuppression

The expression of class II major histocompatibility complex (MHC) molecules on monocytes and the relative proportion of immunoregulatory lymphocyte subpopulations were studied from the blood of eight patients undergoing a cardiac operation. The aim of the study was to reveal mechanisms responsible for depression of cellular immunity and B-lymphocyte activation associated with open-heart surgery. A decreased staining of HLA-DR and even more of HLA-DQ class II MHC molecules was found on the monocyte surface in samples taken 2 and 7 days after operation when compared to preoperative values. The relative proportion of monocytes in mononuclear cells increased after surgery, but within lymphocyte subpopulations only a decrease in total T cells and an increased number of activated (HLA-DR positive) T cells were found, whereas the rations between various T cells subsets remained relatively stable.

Class II major histocompatibility complex restriction of human T cell responses to short ragweed allergen, Amb a V

Although T cells are known to play a crucial role in the induction of IgE synthesis, the class II major histocompatibility complex (MHC) restriction of aeroallergen-induced T cell responses in humans is incompletely defined. We have previously shown that, in allergic Caucasoid individuals, HLA-DR2 and Dw2 (DR2.2) is strongly associated with specific IgE and IgG antibody responses to highly purified Ambrosia (ragweed) allergen, Amb a V, from the artemisiifolia (short) species. For example, 95% of IgE antibody responders to Amb a V were typed as DR2.2. In a novel study of the genetic control of T cell responses to the Amb a V allergen, we have investigated the MHC class II restriction specificity of three CD4, Amb a V-specific T cell clones derived from a DR2.2+ atopic patient, and a polyclonal Amb a V-reactive T cell line from another DR2.2+ patient. We observed proliferative responses of all three clones to Amb a V only when either HLA-DR2.2 or DR2, Dw12 (DR2.12; found on Mongoloid populations) was present on the antigen-presenting cells, regardless of the HLA-DQ phenotype of the cells. Moreover, the responses of T cell line and clones were abolished by anti-DR but not by anti-DQ nor by anti-DP monoclonal antibodies, and, significantly, anti-DR alpha/beta I2 (anti-DR alpha /beta Iw15/w16; anti-"DR2b") monoclonal antibody blocked, in a dose-dependent manner, the cloned T cell responses to Amb a V. These findings demonstrate that DR alpha/beta I2.2 (DR alpha/beta I1501) and DR alpha/beta I2.12 (DR alpha/beta I1502) are functional in the restriction of the T cell recognition of Amb a V. These findings also illustrate the power of the allergy model for definitive investigation of the molecular basis of the human immune response.

Allorecognition of HLA-DR and -DQ transfectants by human CD45RA and CD45R0 CD4 T cells: repertoire analysis and activation requirements

We have investigated the requirements for allogeneic stimulation of human CD4 T cells using HLA class II products expressed on various cellular backgrounds. Human (class II-negative RJ2.2.5 mutant) B cell lines transfected with HLA-DR or -DQ cDNA clones were efficient stimulators for highly purified CD4 T cells. HLA-DR-transfected mouse L cells or IFN-gamma-induced human fibroblasts, although able to function as accessory cells for T cell responses to the mitogen PHA, failed to stimulate strong T cell alloresponses. On the basis of these observations, we have employed class II transfectants to address the following questions: (a) do CD45RA and CD45R0 subpopulations differ in their allogeneic activation requirements, (b) are these subpopulations skewed in their recognition of HLA-DQ vs. HLA-DR in a manner which might support the concept that CD45RA T cells are involved in HLA-DQ-restricted suppressor inducer functions and (c) by using transfectants expressing individual HLA-DR or -DQ heterodimers in combination with limiting dilution analysis, can one for the first time obtain estimates of precursor frequencies for allogeneic cells recognizing each of these class II isotypes? Our results show that CD45RA and CD45R0 T cells respond comparably to optimal numbers of stimulator cells. However, when CD45RA and CD45R0 T cell populations depleted of endogenous accessory cells were cultured with limiting numbers of stimulator cells, CD45R0 cells generally responded more strongly, consistent with the elevated levels of various adhesion molecules known to be expressed by this population. Further, we found a similar representation of responses to HLA-DR and -DQ antigens among populations expressing CD45RA and CD45R0 isoforms. Finally, the precursor frequencies of allogeneic CD4 T cells responding to particular HLA-DR alleles were higher than to -DQ, but only by a factor of about 1.6, indicating that HLA-DQ recognition may occur more frequently than implied from previous antibody blocking studies.

MHC-restricted autoantigen-reactive T cell clones in multiple sclerosis

Multiple sclerosis is a demyelinating disease of the central nervous system with genetic, viral and autoimmune characteristics. Myelin basic protein (MBP) is a suspected target autoantigen since it induces experimental autoimmune encephalomyelitis, an animal model closely resembling multiple sclerosis. The disease is mediated by Class II restricted, MBP-reactive T cells possessing the T helper/inducer phenotype. In the present study, we have isolated MBP-reactive T cell clones from the peripheral blood of a chronic progressive multiple sclerosis patient. The clones displayed blastogenic memory responses when rechallenged with the autoantigen and irradiated autologous lymphocytes. MBP recognition by the autoantigen-reactive T lymphocytes was restricted by major histocompatibility complex Class II antigens. Both CD4+8- and CD4-8+ MBP-reactive T cell clones were obtained.

A supertypic HLA-DP specificity defined by two human-human hybridoma antibodies (TrB50; TrE11)

We here report two human-human hybridoma antibodies: TrB50 (IgG) and TrE11 (IgM), derived from the same donor. They displayed an identical reaction pattern with 76 Epstein-Barr virus-transformed cell lines. Of these, 29 lines were completely HLA-typed and both antibodies recognized all cells expressing DPwl (six lines), DPw3 (five lines), or DPw5 (three lines). In addition, they bound to one out of four DPw2+ cells and three out of four DPblank+ cells. This specificity correlated strikingly with a characteristic DP beta amino acid sequence (DEAV) at positions 84-87 that had been determined by others. Binding of 125I-labeled TrB50 to lymphoblastoid cells was inhibited by unlabeled IVA-12 (anti-DR + DP monomorphic) and by TrE11. Furthermore, antigens in lysates from TrB50+TrE11+ cells cross-linked TrB50 and TrE11 to the monomorphic anti-DP monoclonal antibody B7/21. Collectively the data provide strong evidence that the epitopes reside on DP molecules. TrE11 can be used to type for this DP beta supertypic specificity by microcytotoxicity using isolated blood B lymphocytes as targets or by a rosette assay directly on whole blood.

HLA class II restriction specificity of Dermatophagoides spp. reactive T lymphocyte clones that support IgE synthesis

The results of recent experiments investigating the restriction specificity of cross-reactive, or Dermatophagoides farinae-specific, T cell clones isolated from an atopic individual with perennial rhinitis are reviewed. The restriction specificity was examined using serological inhibition, allogeneic presenting cells and murine fibroblasts expressing HLA-D region products. Although serological inhibition studies suggested that DR class II proteins were the major restriction elements used, the patterns of recognition observed with the allogeneic cell panel were complex, generally failing to correlate with the serologically defined MHC class II specificities. Analysis of the restriction patterns indicated that the majority of the T cell clones were restricted by DR beta III gene products and this was confirmed using murine fibroblasts expressing DRw52. DR beta I gene products functioned as restriction elements in the recognition of house dust mite allergen by the other clones. In an in-vitro model of allergen-dependent IgE synthesis, both DR beta I and DR beta III class II restricted T cells could be shown to provide functional help for IgE synthesized by autologous B cell-enriched populations.

Specificity of HLA restricting elements for human nickel reactive T cell clones

In order to study the fine specificity of HLA class II restriction, we have established nickel specific T cell clones from a nickel allergic patient. Cells were cloned by limiting dilution after primary stimulation and selection of nickel specific blasts. Several clones were established which were all shown to carry the CD4 marker. All clones were shown to be completely blocked by monoclonal antibodies directed against DR antigens, but unaffected by antibodies against DQ or DP, thus demonstrating their DR specificity. For the study of HLA class II restriction, a panel of cell donors was carefully HLA typed by including the use of DRB and DQB cDNA probes. Specificity analysis, using allogeneic antigen presenting cells, revealed that the clones were either restricted to DR3- or DR4-like molecules, which is consistent with the fact that the donor was DR3, DR4 positive. However, the studies also revealed that the fine specificity of the DR3 and DR4 restriction could not be completely assessed by serological and genomic typing of panel cells. This indicates that cellularly defined HLA restriction elements recognized by T cells cannot be defined properly with available class II typing methods, and the results of these experiments documented the additional polymorphism of class II restriction elements. The clonal specificity analysis has shed further light on the biologically relevant level of DR polymorphism.

The DR3(w18),DQw4 haplotype differs from DR3(w17),DQw2 haplotypes at multiple class II loci

The polymorphism of HLA class II molecules in man is particularly evident when comparisons between population groups are made. This study describes a DR3 haplotype commonly present in the American black population. Unlike the Northern European population, in which almost all DR3 individuals are DQw2, approximately 50% of DR3-positive American blacks express a DQw4 allelic product. This study characterizes the DR subregion of that haplotype. cDNA sequence analysis has revealed a DR beta gene which differs at several positions from previously described DR3 beta 1 genes. It is postulated that a gene-conversion-like event with a DRw52 beta gene as donor has generated some of these differences. The haplotype carries a DRw52a allele as defined by oligonucleotide hybridization studies. DNA restriction fragment analysis using a family and several unrelated individuals has allowed us to identify DR alpha and beta fragments associated with the DR3(w18),DQw4 haplotype. The most striking observation is that the DR3(w18),DQw4 haplotype differs from DR3(w17),DQw2 haplotypes at multiple class II loci. Several genetic mechanisms including reciprocal recombination, gene conversion, and point mutation were involved in generating the differences between these haplotypes. Once established, the DR3(w18),DQw4 haplotype appears to be relatively stable in the population.

Positive selection of Tac- (CD25) positive cells following T-cell activation. Use of immunomagnetic separation and implications for T-cell cloning

We have investigated if positive selection for cells expressing activation antigens, which appear on the cell surface during T-lymphocyte activation, could be used for cloning purposes. For this purpose, we used paramagnetic, monodisperse Dynabeads coated with anti-Tac monoclonal antibody, which recognizes CD25 (interleukin-2 receptor light chain). After the first 6-12 h of a primary response, depletion of Tac+ cells could largely abrogate the specific response. This indicated that the specifically responding cells were found among the Tac+ population. T-cell cloning was thus performed on Tac+ blasts positively selected after 18 h of a primary response, at day 6 of a primary response or during secondary stimulation, and gave a high percentage of specific clones. This method is thus a good alternative to established techniques.

Expression of HLA-DQ, -DR, and -DP antigens in normal kidney and glomerulonephritis

Expression of the defined subtypes of HLA-class II antigens DQ, DR, DP, as well as of a putatively new HLA-class II determinant DY was evaluated with specific monoclonal antibodies on frozen sections of 15 normal kidneys, as well as of renal tissue of 65 patients with different forms of glomerulonephritis (GN). In normal kidney HLA-DR and/or -DY versus DQ or DP antigens were shown to be differentially expressed on subpopulations of glomerular and interstitial cells, as well as vascular endothelia. Normal proximal tubular epithelia lacked HLA-DQ and -DP antigens, but carried -DY and variably -DR products constitutively. In comparison, aberrant presence of HLA-DQ and/or -DP antigens was found on proximal tubular cells in the majority of patients with rapidly progressive (RPGN), membranoproliferative GN (MPGN), or focal glomerular sclerosis (FGS), but more rarely observed in other forms of proliferative or non-proliferative GN. In addition all cases with RPGN revealed reduction of HLA-DQ, -DR, -DP or -DY+ glomerular cells. Decline of HLA-DP and/or -DR+ glomerular cells was variably seen in mesangioproliferative glomerulonephritis (MesPGN) and MPGN, whereas in FGS HLA-DQ antigens appeared to be increased in glomeruli. HLA-DQ, -DR, -DY+ interstitial cellular infiltrates were present in RPGN, FGS and MPGN and only occasionally occurred in other forms of GN. Altered renal expression of HLA-class II antigens may indicate specific sites of immunologically-mediated kidney injuries in GN.

Analysis of HLA-DR glycoproteins by DNA-mediated gene transfer. Definition of DR2 beta gene products and antigen presentation to T cell clones from leprosy patients

We have used DNA-mediated gene transfer to express HLA class II molecules in mouse L cells for serological, biochemical, and functional analysis. cDNA clones encoding the DR2 beta a and DR2 beta b products of the DR2Dw2 haplotype were subcloned into a mouse Moloney leukemia virus-based expression vector (pJ4) and transfected separately into mouse L cells together with a HLA-DR alpha/pJ4 construct. These transfectants have allowed differential analysis of the two DR2 beta products in a manner normally prohibited by the concomitant expression seen in B cells. Two-dimensional SDS-PAGE analysis of the transfectants defines the more acidic beta chain as the product of the DR2 beta a sequence, and the more basic chain as the product of the DR2 beta b sequence. The LDR2a transfectants present antigen efficiently to M.leprae-specific T cell clones and are capable of presenting synthetic peptide, 65-kD recombinant mycobacterial antigen and M.leprae. Of the DR2Dw2-restricted T cell clones we have tested, all use the DR2 beta a chain as their restriction element. Inhibition studies with mAbs demonstrate the dependence of presentation by the transfectant on class II and CD4, while mAbs against LFA-1, which substantially inhibit presentation by B-lymphoblastoid cell lines, do not inhibit transfectant presentation.

B cell growth factor (BCGF) secreting human T cell clones reactive to a soluble glycoprotein antigen, streptococcal antigen (SA)

A panel of human T cell clones bearing exclusively the helper (T4) phenotype and showing reactivities to a soluble glycoprotein antigen (185,000 dalton Mol. Wt. Streptococcal antigen, SA) is described. Two of these clones namely, SA 1.53 and SA 1.82, are found to co-produce B cell growth factor (BCGF) and interferon-gamma (IFN-gamma) in the absence of interleukin 2 (IL2) upon stimulation with phytohaemagglutinin (PHA) or the specific antigen in the presence of irradiated autologous antigen-presenting cells (APC). Secretion of the lymphokines is genetically restricted in part by DR molecules that are expressed on the cloned cells and APC. Produced BCGF is differentiated from the BCGF-promoting property of IFN-gamma in that only IFN-gamma activity, but not BCGF activity is removed and inhibited by anti-IFN-gamma antibodies. Exogenous IL2 induces secretion of BCGF and IFN-gamma of the cloned cells, an observation which involves interaction of IL2 with IL2 receptors. An analysis of the proliferative responses to antigen of the T cell clones shows that BCGF-producing clones, unlike those that secrete IL2, fail to proliferate significantly to specific antigen restimulation.

DY determinants, possibly associated with novel class II molecules, stimulate autoreactive CD4+ T cells with suppressive activity

A set of T cell clones (TCC) isolated from HLA-DR-, Dw-, DQ-matched allogeneic MLCs was found to proliferate autonomously when stimulated with cells carrying a wide range of class I or II specificities. This apparently unrestricted proliferation was relatively weak, and only low levels of IL-2 were present in the supernatants of stimulated cells. Autologous as well as allogeneic PBMC and B lymphoblastoid cell lines (B-LCL) were capable of stimulating such clones, which were also restimulated by suppressive, but not by helper, TCC. Moreover, such clones displayed the unusual property of autostimulation. mAb inhibition experiments suggested that class II- or class II-restricted antigens were involved in stimulation. Thus, certain "broad" mAbs (TU39, SG520) reacting with multiple locus products inhibited activation of these reagents, but none of those reacting more specifically with DR (TU34, TU37, L243, Q2/70, SG157), DQ (TU22, SPV-L3, Leu 10), or DP (B7/21), or mixtures of these mAbs, were able to do so. Evidence from sequential immunoprecipitation experiments suggested that mAb TU39 bound class II-like molecules other than DR, DQ, and DP on TCC and B-LCL, and it is therefore proposed that such putative novel class II-like molecules may carry the stimulating determinants for these autoreactive clones. DY-reactive clones lacked helper activity for B cells but mediated potent suppressive activity on T cell proliferative responses that was not restricted by the HLA type of the responding cells. Suppressive activity was induced in normal PBMC by such clones, as well as by independent suppressive clones, which was also inhibited only by mAb TU39. These findings lead to the proposal that DY-reactive autostimulatory cells may constitute a self-maintaining suppressive circuit, the level of activity of which would be regulated primarily by the availability of IL-2 in the microenvironment.

New Dw8 associated class II specificities defined by cytotoxic T lymphocyte clones

Two Leu2(-), Leu3(+), Leu4(+) human cytotoxic T lymphocyte (CTL) clones, BE-11 and AF-3, were generated against Epstein-Barr virus (EBV)-transformed cell line GI (Dw8/DRw8/DQWa homozygous). Blocking experiments with various monoclonal antibodies (MoAbs) revealed that the former recognized the DR molecule and the latter recognized the DQ molecule, respectively. Panel studies showed that CTL clone BE-11 lysed not only DRw8-positive cells but also DR1-positive ones. CTL clone AF-3 exhibited cytotoxicity against only Dw8/DRw8/DQWa typed cells. Until now, such specificities have not been defined serologically or biochemically. These results demonstrated that the previously unknown DR and DQ specificities could be defined by CTL clones, suggesting that CTL clones might be especially valuable tools for investigating the structural polymorphism of HLA antigens.

Molecular localization of LB-Q1, a DRw52-like T-cell recognition epitope and identification at the genomic level of associated shared hybridizing fragments

In this paper we report on the molecular localization of LB-Q1, a supertypic HLA class II determinant which we previously identified by the use of proliferative T cells. The population distribution shows that each of the DRw52 associated specificities DR3, DR5, and DRw6 may occur with and without LB-Q1. DNA from nine DR3, six DR5, and 14 DRw6 homozygous B-cell lines were digested with the enzymes TaqI, EcoRI, and PvuII. Using a DR beta cDNA probe, shared hybridizing fragments were observed that correlate completely with the presence or absence of LB-Q1. T-cell recognition of LB-Q1 can be blocked with a monoclonal antibody (7.3.19.1) which in some haplotypes selectively reacts with the DR beta III chains, but cannot be blocked with a monoclonal antibody (I-LR2) reacting in those same haplotypes exclusively with DR beta I chains. Therefore, LB-Q1 maps to the DR beta III molecule. These data suggest the occurrence of relatively frequent previous recombinations between the two DR beta chain genes present in DRw52 haplotypes.

Major histocompatibility complex (MHC) restricted antigen recognition: high frequency of human T-cell clones recognizing novel MHC class II determinants

We have used antigen-specific human T-cell clones to study the relationship between MHC and antigen recognition specificities expressed by T cells. Tetanus toxoid (TT)-specific T-lymphocyte clones were derived from a immunized HLA-DR2,7 heterozygous donor by limiting dilution from peripheral blood mononuclear cells (PBM) restimulated with TT in vitro. Clones were screened for MHC-restricted antigen recognition against antigen-presenting cells (APC) from a panel of HLA-typed donors, using an in vitro T-cell proliferation assay. Several distinct patterns of antigen recognition were identified. In addition to T cells that recognized TT in association with donor class II MHC antigens, we found clones that simultaneously expressed self-restricted antigen recognition and alloreactivity, and clones with specificity for antigen in the context of MHC antigens not expressed by the T-cell donor. This was confirmed in inhibition studies using well-characterized monoclonal antibodies against class II MHC antigens to block specific proliferative responses. We propose a possible structure for the determinant recognized by two of the clones. These results suggest that the T-cell antigen receptor undergoes random or antigen-dependent changes in vitro, and that this may be a mechanism for somatic diversification of the T-cell repertoire.

Antigen presenting cells in human decidual tissue. II: Accessory cells for the development of anti-trinitrophenyl cytotoxic T lymphocytes

Antigen presenting cells were isolated from early human decidua or peripheral blood by elution with EDTA of cells that after Ficoll-Paque separation bear receptors for, and have bound to, fibronectin. Decidual antigen presenting cells (DAPCs) co-cultured with TNP-modified autologous T cells induced the development of cytotoxic anti-TNP T lymphocytes with an efficiency comparable to that of peripheral blood antigen presenting cells (PAPCs). Treatment with anti HLA-class II antibody plus complement and UV radiation resulted in substantial inhibition of the accessory cell function. The T cell mediated lysis of TNP-modified targets is restricted by the major histocompatibility complex. Our results show that HLA-class I molecules are the most prominent restriction elements. The relevance of these data to the immunological mechanisms operating at the feto-maternal interface is discussed.

Importance of HLA-DQ and -DP restriction elements in T-cell responses to soluble antigens: mutational analysis

We describe a new approach to delineating the restriction elements used by antigen-specific human T-cell lines. EBV-transformed B cell lines and congenic HLA class II antigen-loss mutants are used to present soluble antigen to immune T cells. In this way it is possible to assess the independent contribution of individual class II loci to the restriction repertoire of the T cells. In contrast to results obtained with other methods of restriction element analysis, we find that approximately 40% of the T-cell response to several antigens is restricted by non-DR class II molecules. Both mutational analysis and blocking by class II specific monoclonal antibodies demonstrate that the non-DR restricted responses derive from DQ and DP-encoded determinants. We also find specific DR/DQ haplotype preferences for the presentation of some but not all antigens. Using a mutant that expresses only the DQ1 molecule, and is derived from a DR1, DQ1 parent line, we demonstrate a functional split of serologically defined DQ1 molecules consistent with the electrophoretic variation reported between DQ1 molecules linked to DR1 and those linked to DR2. Pairs of mutants that differ by expression of a single class II protein reveal a much broader use of available class II restriction elements than previously recognized.

Trinitrophenyl reactive T-cell clones in functional and molecular analysis of the HLA-D region

We believe that the approach we have utilized contributes to more complete understanding of the role of HLA class II molecules in presentation of antigen to T lymphocytes and helps to resolve paradoxes presented by earlier studies in which class II-associated restrictions were not apparent. The approach has depended upon development of a library of cloned TCL reactive to a particular haptenic determinant in various class II MHC contexts. It employed initial screening for MHC restriction by analysis on allogeneic stimulator cell panels that could be confirmed or clarified by antibody blocking experiments employing mAb of defined specificities. This has led to clear identification of TCL restricted to recognition of TNP in the context of each of the major class II molecular species, DR, DQ and DP. It has also raised the intriguing and novel possibility that in some instances, at least for DP, T-cells may employ restricting elements, as revealed by mAb blocking, that are either nonpolymorphic or of very low polymorphism. Finally, where important functional polymorphisms have been identified at apparent variance from defined serological specificities, it has been possible to correlate antigen recognition with molecular polymorphisms defined at both the protein level, by amino acid sequencing, and the genomic level by restriction enzyme polymorphisms. As these approaches are combined with new molecular genetic techniques for generation of novel class II constructs, it seems likely that important, but as yet unresolved, questions relating to the nature of the ternary complex involving antigen, MHC molecule and T-cell receptor will be resolved.

Presentation of soluble antigen to human T cells by products of multiple HLA-linked loci: analysis of antigen presentation by a panel of cloned, autologous, HLA-mutant Epstein-Barr virus-transformed lymphoblastoid cell lines

Epstein-Barr virus-transformed human B lymphoblastoid cell lines (EBV-LCL) can present soluble antigens to antigen-primed T lymphocytes. In this study, we used HLA antigen-loss mutants of an EBV-LCL line (LCL 721) to demonstrate that the presentation of a soluble antigen from Candida albicans (CAN) by EBV-LCL to primed T cells can be restricted by multiple HLA determinants. Haplotype-deletion mutants that contained only the maternal or only the paternal HLA-haplotype were used to demonstrate the preferential role of autologous HLA antigens in presenting soluble antigens to Candida-primed T cells from the donor of LCL-721, and to T cells from her mother and father. Immunoselected mutants of LCL-721 showing a variety of distinct phenotypes that are deficient in HLA-DR, DQ, or DP antigen expression were tested as antigen-presenting cells. The antigen-presenting ability of these class II deficient EBV-LCL variants weakened with progressive loss of class II HLA determinants expressed on the cell surface. Our study, therefore, provides evidence for multiple HLA restriction determinants, including HLA-DR, DQ, and DP. Furthermore, LCL lacking all HLA-DR, DQ, and DP expression because of homozygous deletion of these MHC class II genes still presented CAN and Tetanus toxid (TET), although to a much lesser degree than presented by LCL-721. This suggests that determinants other than DR, DQ, and DP which are expressed on these EBV-LCL may also function as restriction elements for the proliferative T-cell response to soluble antigens.

Comparison of HLA-Dw1 and -Dw2 positive adherent cells in antigen presentation to heterozygous T-cell lines: a low rubella antigen-specific response associated with HLA-Dw2

T-cell lines specific for purified tuberculin (PPD), rubella, and herpes simplex virus (HSV) antigens were established from two Dw1/w2 heterozygous subjects. Fresh peripheral blood monocytes from healthy individuals with shared and non-shared D-antigens were used as presenting cells and the T-cell lines as responders in lymphocyte blast transformation assays with specific antigens. An HLA-restricted reaction was seen with all the antigens, although the PPD- and HSV-specific cell lines reacted stronger than rubella-specific lines when the specific antigens were presented by monocytes not sharing the D-antigens. A significantly lower response was seen when rubella antigen was presented by Dw2 positive monocytes as compared to response promoted by Dw1 positive monocytes (p less than 0.0001, Mann-Whitney U-test), whereas no such difference was seen in responses to PPD or herpes simplex antigen.

Molecular characterization of a subtype of DQw1 recognized by hapten-specific T cells

Previous studies of HLA-restricted antigen recognition by cloned T cells have frequently demonstrated reactivity that did not correlate precisely with the expression of serologically defined HLA specificities. To further explore such discrepancies, we utilized monoclonal antibody (MoAb) blocking, partial NH2-terminal amino acid sequencing, and Southern blot hybridization techniques to analyze the fine specificity of four autologous trinitrophenyl-specific T cell lines restricted to DR2-linked epitopes. MoAb blocking studies demonstrated that two of these lines recognized determinants on DR molecules while the other two recognized determinants on the same molecule that expresses the DQw1 determinant. However, these latter two lines appeared to recognize a DQw1-related determinant found primarily in association with DR2, but not the other DQw1-associated DR alleles, DR1 and DRw6. To ascertain whether these lines were defining a functional split of DQw1, we performed partial NH2-terminal amino acid sequencing of the molecules precipitated with a DQw1-specific MoAb (Genox 3.53) from different stimulator lines. The results showed that these T cell lines recognized a subtype of DQw1 that is in linkage disequilibrium with DR2. Moreover, we identified characteristic restriction fragment length polymorphisms with a DQ beta-specific cDNA that correlated with stimulatory capacity for the DQw1-restricted lines. These results demonstrate that: DQ molecules may provide restriction determinants that are incorrectly assigned to DR molecules on stimulator panel analyses; cloned antigen-specific T cell lines recognize polymorphic regions of class II molecules not distinguished by either conventional typing antisera or xenogeneic MoAb; and the DQw1 epitope(s) is located on a heterogeneous group of DQ molecules that differ from each other in the primary sequence of their beta chains.

Recognition of an HLA-DPw1 specific alloantiserum raised by planned immunization

This study reports identification of the first alloantiserum specific for a single HLA-DP allele and presents valuable technical information for the serological detection of the HLA-DP gene product. Serological detection of the HLA-DP gene products was undertaken by analyzing a large number of alloantisera against an HLA-DP characterized, monocyte depleted, B-lymphocyte reference panel. After absorption of contaminating DR antibodies, one alloantiserum (SOW) which had been raised by planned immunization, was shown to have a correlation coefficient of 0.91 with DPw1 as defined by primed lymphocytes. No association was seen with any other HLA-A,-B,-C,-D,-DR, or -DQ specificity in either population or family studies. The HLA-DP typing of the serum donor and immunizing recipient support the conclusion. Evidence is presented which suggests that expression of the DP molecule is not stable, at least as detected by conventional microcytotoxicity techniques.

Antigen-presenting cells in human decidual tissue

The responses of peripheral blood human T lymphocytes supported by decidual antigen-presenting cells (DAPCs) to a variety of immunogenic stimuli were studied and compared to those of T cells supported by peripheral blood antigen-presenting cells (PAPCs). Antigen-presenting cells were isolated from early normal decidual tissue or peripheral blood by elution with ethylenediamine tetraacetic acid of cells that after Ficoll-Paque separation bear receptors for all have bound to fibronectin. DAPCs pulsed with soluble or particulate antigens induced proliferation of T cells with an efficiency equivalent to PAPCs. Decidual tissue APCs also showed the ability to stimulate auto- and alloreactivity. Treatment with anti-human lymphocyte antigen (HLA) class II antibody and ultraviolet radiation resulted in substantial inhibition of the accessory cell function of DAPCs as well as of PAPCs. Bromodeoxyuridine and light treatment of alloreactive T cells generated in vitro was used to demonstrate that DAPCs primed with a synthetic polypeptide antigen (T,G)-A-L can stimulate only HLA class II-compatible T lymphocytes.

Human allospecific TLCs generated against HLA antigens associated with DR1 through DRw8. I. Growth and specificity analysis

To study the fine specificity of the HLA-D region, a panel of human T-lymphocyte clones (TLCs) was generated against alloantigens associated with HLA-DR1 through DRw8. HLA-DR-homozygous peripheral blood lymphocytes (PBLs) were stimulated with DR-heterozygous PBLs in primary mixed lymphocyte cultures for 4 days. Blasts were cloned by limiting dilution at 0.3 cells/well in the presence of 20% T-cell growth factor and irradiated stimulator cells. Viable clones were subsequently tested in proliferation assays against the original stimulator and a limited panel of stimulators bearing relevant DR specificities. Initial primings produced approximately 800 clones; some recognized DR-associated antigens, 70 recognized only their original stimulator, and approximately 50% were nonresponsive. Analysis on extended stimulator panels revealed alloantigenic complexity within similar DR-associated antigens as recognized by TLCs. The data are consistent with evidence that extreme heterogeneity exists within the HLA-D region.

Functional definition of HLA-DR and -DQ epitopes specific for DR2-short, DwFJO haplotype

T-lymphocyte clones specific for the influenza A/Texas virus were obtained by limiting dilution of activated T cells from an HLA A2/3,B7/39,Cw -/-,DR2-short/2 short,DQw1,DwFJO/FJO donor. Among the proliferating clones studied, and irrespective of their antigenic specificities, most of them were restricted by epitope(s) on HLA-DR molecules present only on DR2-short/DwFJO cells but not on DR2-negative or DR2-long positive (Dw2,Dw12,Dw-) cells. Two clones were restricted by epitopes borne by DQ products. Here again, these epitopes were present on DR2-short/DwFJO but not on DR2-long,DQw1 (Dw2,Dw12) cells, indicating that the DQw1 molecules of DR2-long and DR2-short haplotypes are different. Taken together, these results indicate that the DR2-short,DwFJO haplotype is characterized by both HLA-DR- and DQ-specific molecules. Finally, one clone was restricted by an epitope shared by DR products from DR2 short/DwFJO, DRw11, and DRw13 haplotypes. This latter functional determinant has never been described until now.

Despite lack of monospecific anti-DRw13 sera, a corresponding class II determinant can be defined by a DRw13 restricted anti-influenza virus T cell clone

The study of a T3+ T4+ T8- human T cell clone COTC2 with both specific proliferative response and cytolytic activity for influenza A virus infected cells reveals that: the restricting element of this clone is strongly associated with DRw13 molecule(s) as seen by the study of a large panel of antigen presenting cells (APC) and by the observation that monoclonal antibodies (MoAb) specific for DR molecules inhibit its proliferative activity while anti-DQ MoAb do not. These results indicate that there exists a DRw13 associated determinant that can be defined at the functional level by COTC2 recognition despite the absence of monospecific anti-DRw13 serum. In contrast to the results found by other groups, the restriction of this DRw13 restricted clone follows the DRw13 serological definition irrespective of the DW type of the APC. These results indicate that the polymorphism of HLA class II molecules can be further defined at the functional level by monoclonal populations of T cells in conjunction with molecular definition.

HLA class-II-restricted Mycobacterium leprae-reactive T-cell clones from leprosy patients established with a minimal requirement for autologous mononuclear cells

This report describes an effective method for the cloning of Mycobacterium leprae-reactive T lymphocytes with Epstein-Barr-virus transformed autologous B cells as antigen-presenting cells. The two advantages of this method are that it drastically reduces the number of autologous peripheral blood mononuclear cells (less than 10(7) cells) needed to obtain and propagate these T-cell clones (TLC), and that it enables us to expand individual TLC to large numbers of cells (greater than 10(8)). Thus the major obstacles for the cloning of T lymphocytes--especially important with regard to patients--are bypassed. Thus far, TLC from three leprosy patients have been established. These TLC are HLA class II restricted in their M. leprae-directed response. A marked enhancement in antigen responsiveness was observed after further expansion of several TLC, some of which turned from nonresponder into responder TLC. Four tested TLC display strikingly different antigen recognition patterns when tested against a number of other mycobacterial antigens; one TLC so far recognizes only M. leprae antigens.

DO beta: a new beta chain gene in HLA-D with a distinct regulation of expression

The HLA-D region of the human major histocompatibility complex encodes the genes for the alpha and beta chains of the DP, DQ and DR class II antigens. A cDNA clone encoding a new class II beta chain (designated DO) was isolated from a library constructed from mRNA of a mutant B-cell line having a single HLA haplotype. Complete cDNA clones encoding the four isotypic beta chains of the DR1, DQw1, DPw2 and putative DO antigens were sequenced. The DO beta gene was mapped in the D region by hybridization with DNA of HLA-deletion mutants. DO beta mRNA expression is low in B-cell lines but remains in mutant lines which have lost expression of other class II genes. Unlike other class II genes DO beta is not induced by gamma-interferon in fibroblast lines. The DO beta gene is distinct from the DP beta, DQ beta and DR beta genes in its pattern of nucleotide divergence. The independent evolution and expression of DO beta suggest that it may be part of a functionally distinct class II molecule.

Recognition of DP determinants with typing reagents prepared with lymphocytes from Dutch unrelated individuals

In an attempt to make our own set of DP typing reagents, we used lymphocytes from 12 unrelated donors, who were all HLA-A1,2; B7,8; DR2,3; DQW1,2. They all had been previously typed for DP using a reference set of well established reagents obtained from Dr. S. Shaw (NIH, Bethesda). Thirty-six promising responder-stimulator combinations were primed in bulk MLC and tested for their specificity in secondary MLC. All reagents gave reaction patterns which were concordant with the sensitizing DP types, with the exception of those combinations where a donor was used in which DR2 appeared to be associated with a non-DW2 HLA-D type. Over 1,200 reactions obtained with the new reagents were compared with those obtained with the established ones, in six different experiments. High correlation coefficients (r values) were found between the two kinds of reagents. The typings of a panel of individuals with the reference set and with our new typing set revealed an excellent agreement for DP assignments with the two sets, with the exception of the specificity DP4. The DP gene frequencies for random Dutch Caucasoids were defined.

Homozygous typing cell-defined HLA-Dw specificities correlate better than serologically defined HLA-DR specificities with restriction elements for influenza virus-specific proliferative human T lymphocyte clones

Human T lymphocyte clones with specific proliferative response to influenza A virus were derived by limiting dilution from peripheral blood lymphocytes (PBL) after in vitro stimulation with autologous irradiated, virus-infected PBL. Four OKT3+4+8- T lymphocyte clones (TLC) that showed HLA-restricted antigen-specific proliferative responses were used for a detailed analysis of the restriction elements for antigen presentation. None of the clones showed alloreactivity and all required the presence on the antigen-presenting cell of HLA class II antigens of one or other haplotype of the donor. Restriction elements for two clones were correlated with Dw1 rather than DR1, and for two others with Dw6 rather than DRw6. These latter clones showed differential recognition of HLA-Dw6 subtypes as defined tentatively by homozygous typing cells, without relationship to putative serological "splits" of DRw6. One of the Dw6-restricted clones was specific for a Dw6.1 (now Dw18) "subtype," confirmed by family segregation analysis, the other for a broad Dw6 (Dw18 and Dw19) specificity. Studies with a panel of monoclonal antibodies against monomorphic determinants of HLA class II antigens revealed heterogeneous patterns of blocking activity, distinguishing between clones of different restriction specificity. Inhibition patterns were partly as predictable from the known activity of the monoclonal antibody in alloantigeneic PLT systems. These results provide evidence that certain structures that function as restriction elements for antigen presentation also carry alloantigeneic determinants.

Class II determinants recognized by TNP-specific cloned human T cell lines

Cloned human T lymphocyte lines were generated against trinitrophenyl (TNP)-modified autologous cells from four different individuals. By examining the reactivity patterns of 58 of these T cell clones (TLC) on panels of HLA-typed antigen presenting cells and employing monoclonal antibodies (MoAb) for inhibition studies, we have demonstrated that TNP may be recognized in the context of different DR and DP associated determinants. We did not identify any TLC restricted by determinants associated uniquely with DQ. Determinants associated with the expression of DR1,2,4,5, and 7 as well as the supertypic specificities DRw52 (MT2) and DRw53 (MT3) functioned as restriction elements. In addition, at least two antigenically distinct regions of the DP4 molecule appeared to function in the presentation of TNP. One TNP-specific TLC recognized a determinant associated with the expression of DP4 while another recognized TNP in the context of a highly nonpolymorphic determinant on DP which was expressed on all stimulators tested. Monoclonal antibody blocking studies suggest that these two determinants lie on different portions of the DP molecule. These studies demonstrated that both polymorphic and relatively nonpolymorphic restriction determinants on DR and DP may function in the presentation of conventional antigen to autologous lymphocytes.

Implication of structural class II gene polymorphism for the concept of serologic specificities

We have used DNA-DNA hybridization methods to study the relationship of genetic polymorphisms to the established HLA-D region determinants as detected with serological reagents. The supertypic determinants DRw52 and 53 are closely associated with a particular RFLP detected with the DR beta probe, but are seemingly encoded by a distinct beta gene compared to the "conventional" DR antigens. DQw1 is closely associated with a DQ alpha chain polymorphism, whereas the DQw2 and 3 specificities have correlations to RFLP using the DQ beta probe. Additional DQ polymorphism, in linkage disequilibrium with DR but yet without a serological counterpart is also described. Considering the finding that there exist a varying number of DR beta genes in different DR haplotypes (Böhme et al. 1985), from 1 in DRw8 to 3 (or 4) in DR4- and DR7-positive cells, we have made a tentative re-evaluation of the genetic basis for the conventional DR specificities. The combination of cell surface antigens encoded by DR and DQ loci are believed to form the basis for MLC stimulating determinants. We have speculated that a combination of determinants encoded by distinct DR beta genes and in certain instances additional DQ polymorphism is responsible for the DR types. Thus, only a limited variability is observed after DNA-DNA hybridization using DR beta probes. Only DR1-, 2- and 4-positive cells have distinct bands not detected in any other haplotypes, whereas DR3, 5, w6, and w8 can be characterized by a combination of bands, which is the result of hybridization with several DR beta genes. Furthermore, we have suggested that the difference between the DR3 and DRw6 specificities is due to variability with regard to 1 DQ beta gene, and have also made the assumption that DRw6 cells may express a lower concentration of DR locus encoded products compared to DR3-positive cells (Haziot et al. 1985). In addition, we have discussed the genetic basis for so-called DR blanks, implying that an unorthodox combination of DR and DQ determinants forms the basis for difficulties in assigning DR types to such cells in some cases and that "blanks" can be associated with low expression at the cell surface of well-known DR determinants. The use of cDNA and genomic probes for distinct class II genes to elucidate the mechanisms of HLA and disease association has been documented and discussed.

HLA class II restriction repertoire of antigen-specific T cells. II. Evidence for a new restriction determinant associated with DRw52 and LB-Q1

We have studied the HLA class II restriction repertoire of antigen-specific T lymphoblasts (T-LB) in response to purified protein derivative (PPD) and tetanus toxoid (TET), presented by allogeneic antigen-presenting cells (APC). In 102 fully DR(1-w14) mismatched T-LB/APC combinations matching for DRw53 (MT3) had a significant influence on T-LB proliferation (p = 0.0005). Moreover, the supertypic specificity DRw52 (MT2) and LB-Q1 (a new class II determinant in strong linkage disequilibrium with DRw52) appeared to be markers for a new RD (p less than 0.0005). LB-Q1 was most strongly associated with this RD and among DRw52 identical T-LB/APC combinations additional LB-Q1 sharing significantly increased T-LB responsiveness (p = 0.02). DRw52- and LB-Q1-restricted responses could be inhibited by an anti-DRw52 and an anti-DR framework monoclonal antibody, indicating that DR(w52), LB-Q1, and the new RD are located at the same molecule.

Identification, at the genomic level, of an HLA-DR restriction element for cloned antigen-specific T4 cells

Two T4 cell clones (TLC) specific for antigenic epitopes on Chlamydia trachomatis were studied. Using a panel of allogeneic antigen-presenting cells (APC), both TLC were found to be restricted by HLA class II elements closely associated with, but not identical to the DRw5S specificity, as determined by highly selected alloantisera, a monoclonal antibody (mAb), 109d6, and confirmed on the DNA level by determination of restriction fragment length polymorphisms (RFLP) with a DR beta probe. Furthermore, HLA-DR-specific mAb, including 109d6, but not other HLA class II- or class I-specific antibodies inhibited the two TLC, strongly suggesting that the restriction element is expressed by a DR molecule. Using digestion with Hind III restriction enzyme and a DR beta probe, we found a complete concordance between the appearance of a 9.3 kilobase band and the ability of allogeneic APC to restimulate the T cell clones. Thus, the restriction element for these T cell clones appear to be expressed by DR molecules, but can, at present, only be detected at the genomic level.

HLA class II restriction repertoire of antigen-specific T cells. I. The main restriction determinants for antigen presentation are associated with HLA-D/DR and not with DP and DQ

In order to study the HLA class II restriction repertoire in antigen presentation to T cells, T lymphoblasts (T-LB) of ten different HLA class II donors were generated by a simple and rapid technique; peripheral blood lymphocytes (PBL) were restimulated in vitro with purified protein derivative (PPD) or tetanus toxoid (TET), and then propagated in interleukin-2 containing conditioned medium (IL2-CM). These T-LB appeared to be antigen specific and devoid of alloreactivity. Antigen was presented to these T-LB by allogeneic irradiated PBL as antigen-presenting cells (APC) in 179 combinations. T-LB proliferative responses were restricted mainly by determinants associated with HLA-DR and not with -DP or -DQ; in 102 fully DR mismatched T-LB/APC combinations matching for DP or DQ determinants had no significant influence on T-LB responses. For PPD, preferential DR1 restriction was observed, and the results suggest a preferential DRw11 vs. DRw12 restriction for TET. Moreover, DRw13 may be associated with low anti-PPD T-LB responsiveness.

HLA-class II restriction of the proliferative T lymphocyte responses to nickel, cobalt and chromium compounds

Peripheral blood mononuclear cells from nickel and/or cobalt or chromium sensitive patients were stimulated with the appropriate metal compound for 7 days in culture. The transformed blasts were separated from non-transformed small cells on Percoll density gradients. The blasts, maintained in interleukin-2 containing medium and enriched for T cells, were both antigen specific and devoid of alloreactivity. The metal compound primed T cell blasts from all patients showed a good proliferative response on restimulation with the priming compound in the presence of autologous adherent cells (AC). Analysis of HLA class II phenotypes of allogeneic AC that could serve as antigen presenting cells indicated that responsiveness of T cell blasts from most but not all patients could be explained on the basis of HLA-DR as a restricting element. We conclude that products of other class II loci (HLA-DQ and/or HLA-DP) might also serve as restricting elements for a secondary in vitro proliferative response to these metal compounds.

Characterization of Chlamydia trachomatis serotypes by human T-lymphocyte clones

T cells primed to Chlamydia trachomatis serotypes A, F, and K were cloned by limiting dilution. All T-lymphocyte clones obtained reacted only with C. trachomatis antigens. The proliferative capacity of 89 clones was studied with autologous non-T cells as antigen-presenting cells and the chlamydia serotypes A, B, D, F, K, and LGV-2 as antigens. Most of the clones reacted to several of the chlamydia strains, indicating common antigenic determinants. Other T-cell clones reacted with only a few serotypes. On the basis of the proliferation of the T-cell clones to the chlamydia strains and to interleukin-2, different reactivity patterns were obtained, which possibly can be used to differentiate among the chlamydia strains.

Antigen-specific T cell clones restricted by DR, DRw53 (MT), or DP (SB) Class II HLA molecules. Inhibition studies with monoclonal HLA-specific antibodies

T lymphocyte clones (TLCs) specific for Chlamydia trachomatis were obtained after limiting dilution of activated T cells from a single donor, BS (HLA-A3; B7,15; DR1, 4; DRw53; DPw4). Most of the proliferative TLCs obtained apparently used restriction elements on DR1 or DR4 molecules, expressed in the antigen-presenting cells (APC). The restriction pattern of two TLCs, however, closely followed the DRw53 specificity, while one TLC seemed to be restricted by elements on DPw4 molecules. A panel of murine monoclonal antibodies (Mabs) was employed to further dissect the restriction specificities. The proliferative capacity of some of the TLCs was studied with and without Mabs directed against different HLA molecules, using non-T cells, monocytes, and peripheral blood dendritic cells as APC. Two Mabs, 7.2 and D-54, which seem to detect monomorphic determinants on HLA-DR, inhibited both DR- and DRw53-restricted TLCs. One Mab, 109d6 which reacts with DRw53 determinants, selectively inhibited the DRw53-restricted TLCs. The DP-restricted TLC was not inhibited significantly by any tested Mabs, including two Mabs with putative specificity for monomorphic determinants on the DP molecule.

Major histocompatibility complex restriction of tetanus toxoid-specific human T lymphocyte clones

Peripheral blood mononuclear cells (PBMC) from an HLA DRw6/7 individual were stimulated with tetanus toxoid (TT). T cell blasts were cloned by the limiting dilution technique in the presence of TT and irradiated autologous PBMC (iPBMC). Twelve were propagated under interleukin 2 and restimulated weekly with TT and iPBMC. All proliferated specifically in response to TT or either the alpha or beta chain of the toxin molecule. HLA restriction of specific proliferative responses was analyzed using a panel of HLA-typed unrelated donors and selected families, and blocking experiments with anti-HLA class I and class II monoclonal antibodies (mAb). Three types of restriction were observed: (a) autologous restriction; the inhibition observed using anti-HLA DR mAb as well as family studies performed previously with a similarly restricted clone obtained from the same donor suggest an HLA DRw6-linked restriction; (b) an HLA DR7 restriction was found for 2 clones, specific for alpha or beta chain; the identical pattern of inhibition obtained with two different mAb belonging to the same cluster suggests that these clones may be restricted by the same (or a very close) epitope of the HLA DR7 molecule; (c) an unusual restriction pattern was found for one clone; PBMC from more than 80% of donors could present TT whatever their degree of HLA compatibility with the autologous donor. Family studies were unable to disclose any restriction with known class II (or class I) antigens. While no inhibition was observed with anti-DR or -DC reagents, a mAb that recognizes class I antigen when associated with beta 2-microglobulin did inhibit the proliferation of this clone.