Antigen-specific HLA-restricted human T-cell lines. I. An MT3-like restriction determinant distinct from HLA-DR

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.

HLA-D region epitopes associated with juvenile arthritis. Recognition by alloreactive T cell clones and alloantisera

The HLA-D region antigens DR5 (w11,w12), DRw6 (w13,w14), DRw8, DRw52, and DQw1 have previously been shown to be increased in frequency in subsets of patients with juvenile arthritis. Since the HLA-D region is complex (composed of at least 3 subregions encoding multiple molecules, each in turn presenting multiple alloantigenic epitopes), we sought to clarify whether one strongly associated factor might explain the previous findings. To search for the pertinent HLA-D region stimulatory epitopes, alloreactive T cells were primed against DR5 and DRw6 haplotypes and cloned by limiting dilution. Three T cell clones and 1 alloantiserum met the criteria for significant association with juvenile arthritis on patient testing, including DR5, DRw6, and DRw8 haplotypes. Monoclonal antibody blocking revealed that all 4 recognized epitopes on DR subregion products. For 2 of the clones, the relative risks for JA (10.5 and 9.4) were higher than the risks with any other previously described typing reagents.

Antigen presentation by adherent cells from human peripheral blood. Correlation between T-cell activation and expression of HLA-DQ and -DR antigens

The ability of cells with different amounts of HLA-DQ or -DR to support T-cell proliferation in response to foreign antigens was investigated. Adherent cells were stained with monoclonal antibodies and sorted in the fluorescence-activated cell sorter (FACS) into (a) DQ-positive and DQ-negative subsets, with monoclonal anti-DQ; or (b) subsets expressing different density of DR determinants. Expression of HLA-DQ correlated with increased density of DR. The subset of cells expressing detectable DQ and increased density of DR was found to be more efficient in presenting mumps or tetanus toxoid antigen to T cells than were the DQ-negative, low-DR density adherent cells. Similar results were obtained with primary cultures of T cells from blood and with cloned antigen-specific T-cell lines, restricted by a single DR-subregion specificity. Our results suggest that quantitative variation in DR/DQ molecules expressed on monocytes correlates with their ability to support T-cell responses to nominal antigens. It is not clear whether this is due to only class II antigen density on the surface of the accessory cells or whether other factors are involved.

An antiviral T-cell clone defines a functional supertypic specificity shared by different HLA-DR molecules from DR2-short, DRw11, and DRw13 haplotypes

An influenza virus-specific HLA class II-restricted human T4+ clone (Ij) allows us to define a new functional supertypic HLA class II specificity shared by three different haplotypes. Influenza A virus-infected antigen-presenting cells of these three haplotypes, HLA-DR2 short, DRw11, and DRw13, are able to stimulate Ij cells. The same precise viral specificity is seen in all three cases. Proliferation inhibition experiments using HLA-specific monoclonal antibodies demonstrate that HLA-DR products are involved in all cases. However, according to the DR specificity of the antigen-presenting cell, differential blockings by a series of DR-specific monoclonal antibodies suggest that the functional epitope is shared by different HLA-DR molecules. This is confirmed by two-dimensional gel analysis of the HLA-DR beta chains expressed in the three haplotypes.

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.

Molecular localization and polymorphism of HLA class II restriction determinants defined by Mycobacterium leprae-reactive helper T cell clones from leprosy patients

MHC class II molecules carry the restriction determinants (RDs) for antigen presentation to antigen-specific Th lymphocytes. This restriction of T cell activation endows those molecules with a key role in the induction and regulation of antigen-specific immune responses. Moreover, class II molecules are the products of class II immune response (Ir) genes. The polymorphism of these Ir genes leads to genetically controlled differences in immuneresponsiveness between different individuals. An important human example is leprosy, in which HLA class II-linked Ir genes determine the immune response against Mycobacterium leprae, the causative organism of the disease. Since the immune response against M. leprae is entirely dependent on Th cells, the HLA class II-linked Ir gene products may well regulate the immune response by controlling the presentation of M. leprae antigens to Th cells. We therefore have investigated the HLA class II RD repertoire of M. leprae-reactive Th cell clones (TLC) by means of extensive panel and inhibition studies with fully class II-typed allogeneic APCs and well-defined HLA class II-specific mAbs. The TLC studied (n, 36) proliferated specifically towards M. leprae, produced IFN-gamma upon activation, and had the CD3+CD4+CD8- phenotype. The results show in the first place that the majority of the RDs for M. leprae reside on DR and not on DP or DQ molecules. This indicates a major role for DR molecules in the immune response to M. leprae and suggests that these molecules are the main products of M. leprae-specific Ir genes. Furthermore, since the expression of DR molecules is much stronger than that of DP and DQ molecules, these findings suggest that the localization of RDs for M. leprae on class II molecules correlates with the quantitative expression of these molecules. The observation that the RDs on DR molecules coded by a DR4 haplotype were situated only on those DR molecules that are known to be highest in expression can be explained in the same way. Second, four distinct RDs related with but not identical to the Dw13 allodeterminant were carried by the DR+DRw53- (alpha beta 1) molecules of a DR4Dw13 haplotype. Since the known amino acid residue differences between the allelic DR4 related Dw beta 1 chains cannot explain the observed RD-polymorphism, this observation suggests that multiple distinct RDs unique for the DR4Dw13 haplotype are expressed by these molecules. Only 2 of 36 TLC were not restricted by DR.(ABSTRACT TRUNCATED AT 400 WORDS)

Functional roles of human class II antigens in T cell proliferative response. Comparison of the DR and DQ molecules using mouse monoclonal antibodies

The monoclonal antibody (mAb) NC1 recognizing a monomorphic DR determinant and the anti-DQ mAbs PLM2, PLM9, and PLM12 recognizing polymorphic DQ determinants were produced. NC1 reacted with the H1L1 (DR) and H1L2(DRw52, DRw53 and allelic products) complexes of a DR family, while the specificity of PLM12 was DQw3 (previously called TB21). Both PLM2 and PLM9 reacted with the allodeterminant of TA10 (a subtype of DQw3). These three mAbs immunoprecipitated the same H2L3 complex of a DQ family. With the aid of these mAbs, DR molecules but not DQw3 molecules were detected on monocytes in significant quantities. The functional roles of these class II molecules in the T cell proliferative responses to three soluble antigens (PPD, mite, Candida) and alloantigens were examined by blocking assays in vitro. NC1 almost completely inhibited T cell proliferative responses against both soluble antigens and allogeneic antigens. In contrast, PLM2, PLM9 and PLM12 showed no significant inhibitory effects at all. These results indicate that DR and DQ antigens are different in their functional roles as well as their serological and immunochemical characteristics and tissue distributions; these three soluble antigens and the alloantigen were presented in association with determinants residing predominantly on two forms of NC1-reactive molecule, namely the H1L1 and/or H1L2 complex of a DR family but not in association with the DQw3 allodeterminant on the H2L3 complex of a DQ family.

Dw subtypes of serologically defined DR-DQ specificities restrict recognition of cytomegalovirus

We have investigated the relationship between serologically defined (Ia) and T lymphocyte-defined (LD/Dw) determinants in restricted recognition of cytomegalovirus (CMV) by human T lymphocytes. T lymphocytes isolated from CMV seropositive individuals expressing DQw3/DR4/Dw4 antigens were "sensitized" to CMV in vitro; CMV-specific blasts were isolated and tested for their ability to recognize CMV presented by cells expressing different DR4-associated Dw antigens (i.e., Dw4, Dw10, Dw13, Dw14, and Dw15). Similar studies were also performed using T lymphocytes from individuals expressing DQw1/DR2/Dw2 specificities and antigen presenting cells (APC) expressing the DR2-associated Dw/LD subtypes, Dw2, Dw12, and LD-MN2. CMV-specific T cell blasts were used as responding cells in order to reduce nonspecific background alloresponses which occur with allogeneic APC. In all cases it was found that the determinants involved in restricted recognition of CMV were subtypic to the DR-associated Ia specificities. To distinguish whether Dw specificities associated with DQ or with DR molecules, or both, were involved in these responses, we used anti-DR (L243) and an anti-DQwl (S3/4) monoclonal antibodies (MoAb) to block CMV-specific responses. Both MoAb significantly blocked responses, suggesting that determinants associated with both DR and DQ molecules are involved in restricted recognition of CMV by T cells.

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.

The proliferative immune response to autologous Epstein-Barr virus transformed lymphoblastoid cells. II. Studies with HLA class II loss variants demonstrate a role for gene products other than DR and DQ

The Epstein-Barr virus (EBV) transformed lymphoblastoid cell line (LCL-721) and some of its HLA loss mutant derivatives were used to study the immune specificity of the autologous proliferative T cell response to antigens expressed as a result of EBV infection. We have measured secondary and tertiary proliferative responses to well-characterized variants that lack expression of some or all known class II gene products (DR, DQ, and DP). These experiments prove that the region mapping between DR/DQ and glyoxalase I (GLO) of one haplotype controls at least one specific restriction element which is recognized in the autologous response to LCL-721. Furthermore, specific proliferative responses to variants lacking expression of all known class II gene products indicate the recognition of determinants other than DR, DQ, and DP.

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.

Presentation of Candida albicans and purified protein derivative soluble antigens by Epstein-Barr virus-transformed human lymphoblastoid B-cell lines

Cells other than the macrophage can function as antigen-presenting cells (APCs). These class II-bearing accessory cells include dendritic cells, epidermal Langerhans cells, B cells, murine B-cell tumors, and human Epstein-Barr virus-transformed lymphoblastoid cell lines (EBV-LCL). We investigated the ability of EBV-LCL to present two soluble antigens, Candida albicans and purified protein derivative of tuberculin (PPD). The EBV-LCL derived from B cells of two different individuals can present both antigens to bulk cultures of autologous antigen-primed peripheral blood lymphocytes. The responses of PPD-reactive T-cell clones were weaker to PPD when presented by EBV-LCL than by PBL-APCs, with some clones responding only to PPD presented by PBL-APCs. This suggests that EBV-LCL are not equivalent to PBL monocytes in APC function, and that expression of class II major histocompatibility complex antigen is not sufficient in enabling antigen-presenting capability.

An association between HLA DRI and lichen planus

Serological typing for HLA Class II antigens in 72 patients with lichen planus (LP) revealed a highly significant association with HLA DRI and MTI (DQWI). DRI was present in 80% of patients with generalized LP, 54% with localized LP, 56% of patients with drug-induced LP and in 31% of patients with mucosal LP, compared with 25% of normal controls. MTI (DQWI) was found in 83% of the LP group and 62% of the normal controls. These findings strongly suggest a genetic predisposition or susceptibility to the development of generalized LP and perhaps also to drug-induced LP.

Recognition of class II molecules by human T cells. I. Analysis of epitopes of DR and DQ molecules in a DRw11, DRw52, DQw3 haplotype

The HLA-D region of individuals with the DRw11, w52, DQw3 haplotype encodes multiple molecular products of three distinct subregions, DR, DP, and DQ. Since each molecule can carry multiple stimulatory epitopes, the repertoire of allogeneic T-cell responses to determinants of this haplotype can be quite large. In the present experiments, alloreactive cloned T-cell lines recognized six distinct epitopes associated with DRw11, DRw52, DQw3 haplotypes. Panel studies established that three epitopes were DRw11-like and three were DRw52-like. Blocking with monoclonal antibodies showed that two DRw11-like epitopes were carried by DR-subregion products and one DRw11-like epitope was carried by DQ-subregion molecules. DRw52-like epitopes were detected on separate DR subregion-encoded molecules. One of them carried both DRw11- and DRw52-like epitopes, the other carried two of the DRw52-like epitopes. These epitopes, which represent functional units that trigger T-cell responses, can be detected at the present time only with the methods used in this report. Conventional allogeneic T-cell responses represent the summation of responses to multiple epitopes encoded by different D-subregion genes.

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.

Quantitative and qualitative differences in HLA-DR molecules correlated with antigen-presentation capacity

The monoclonal antibodies 7.3.19.1 (anti-DRw52-like) and B8.11.2 (anti-DR framework) were used for the isolation and characterization of HLA class II molecules expressed by HLA-DR3 and DR5 homozygous B cell lines. Sequential immunoprecipitation studies demonstrated that from these cells class II molecules can be isolated which are characterized by the presence or absence of DR framework (DR) and DRw52-like (DRw62) determinants: (DR+, DRw52+), (DR+, DRw52-) and (DR-, DRw52+). The DR3 donor cells appeared to express only the (DR+, DRw52+) and (DR-, DRw52+) class II molecules whereas DR5-positive cells express only the (DR+, DRw52+) and (DR+, DRw52-) class II molecules. Besides qualitative differences some of the above-mentioned molecules appeared to differ in their levels of expression. To investigate whether this might have functional implications, cells with the HLA-DR3 and -5 haplotypes were used to present antigen purified protein derivative of tuberculin (PPD) to PPD-specific T cell lines and the blocking capacity of the two monoclonal antibodies 7.3.19.1 and B8.11.2 was determined. A remarkable correlation was observed between the type of class II molecule blocked by these monoclonal antibodies and its quantitative expression. However, (DR-, DRw52+) molecules, clearly expressed by DR3 cells, were not involved in the presentation of PPD. This indicates that not only quantitative but also qualitative aspects may play a role in the selection of the type of class II molecule that will be involved in antigen presentation.

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.

Genetic complexity and expression of human class II histocompatibility antigens

The genes encoding nearly all of the serologically defined class II antigens of the major histocompatibility complex have been isolated. Three class II loci have been studied in great detail. The DR region contains a single alpha gene and 3 beta chain genes, 1 of which is a pseudogene. The DR alpha chain gene has been linked to a DR beta gene which encodes a beta protein which contains the serological determinant MT3. A second cosmid cluster contains 2 beta genes, 1 of which encodes the DR4 allospecificity. The identification of these genes has been made by the comparison of amino terminal sequences of DR molecules obtained from a DR4 cell line and the deduced protein sequences of the beta 1 exons from cosmid and phage clones. A conserved element including the promoter and signal sequence is found at the 5' end of each of the 3 DR beta genes. Additionally, this element occurs three more times in the DR region, raising the question of whether additional beta chain genes might be found. The DQ region contains 2 pairs of genes, 1 of which encodes the DQ antigen. The 2nd pair of genes, called DX alpha and beta, appears to be capable of expressing a DQ-related product, although, to date, there is no evidence for its expression. The DP region also contains 2 pairs of genes. One pair encodes the DP antigen while the 2nd alpha-beta pair is shown to be composed of pseudogenes. The location of polymorphic regions in these genes and aspects of their relationship to the serology, evolution, and function of the class II MHC are discussed. The control of expression of class II genes by gamma-interferon has been examined. The promoters of class II genes are characterized by two conserved sequences common to all alpha and beta chain genes as well as by conserved sequences specific for either alpha or beta chain genes. In addition to studies of expression by DNA-mediated gene transformation, a system for the gene transfer of MHC antigens utilizing transmissible retrovirus vectors is described. Retrovirus vectors have been used to transmit DR alpha, DR beta, and the invariant chain (gamma) sequences to recipient cells with resultant expression of these proteins.

The proliferative immune response to autologous Epstein-Barr virus-transformed lymphoblastoid cells. I. Studies with HLA haplotype loss variants demonstrate a role for MHC-linked genes

The human Epstein-Barr virus transformed lymphoblastoid cell line (EBV-LCL) 721 and MHC haplotype loss variants derived from it were utilized to dissect the functional role of MHC genes in the proliferative response of autologous T lymphocytes to EBV-LCL. LCL-721 is heterozygous at all phenotypically defined MHC loci. One type of LCL-721 variant expresses only determinants encoded by the maternal (m) haplotype and the other expresses determinants encoded by the paternal (p) haplotype. Autologous (individual A) primary proliferative responses are strong to each type of haplotype deletant. The strong tertiary responses to the priming haplotype in comparison to the relatively weak responses to the reciprocal haplotype indicate that MHC linked genes encoded by each haplotype are important in the autologous response to EBV-LCL. Similar specific tertiary responses are observed when peripheral blood lymphocytes (PBLs) from the donor's mother are used as responding cells. Allogeneic responses were also studied by priming PBLs from unrelated donors with the haplotype deletants. Quantitative comparisons of the proliferation by primed allogeneic and autologous lymphocytes stimulated by irradiated PBLs from donor A and her mother, and by LCL-721 and its variants, show that some of the tertiary responses involve specific recognition of EBV-LCL while others detect recognition of alloantigens.

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.

Molecular characterization of MT3 antigens by two-dimensional gel electrophoresis, NH2-terminal amino acid sequence analysis, and southern blot analysis

The monoclonal antibody 109d6, which recognizes major histocompatibility antigen MT3-like serologic determinants, has been used to characterize the molecules bearing this determinant in HLA-DR4 and -DR7 homozygous cell lines by two-dimensional gel and sequencing analyses. By these two criteria, these molecules are identical to each other. Southern blot analysis of genomic DNA from HLA-DR1 through -DR7 homozygous cell lines with DR beta-chain gene probes reveals a striking similarity in the pattern of hybridizing fragments between DR4 and DR7 haplotypes and among DR3, DR5, and DRw6 haplotypes reminiscent of the MT3/MT2 allodeterminant distribution. The sharing of the MT2 determinant between DR3, DR5, and DRw6 haplotypes and of the MT3 determinant between DR4 and DR7 haplotypes is part of a broader "homology," which may be a consequence of more recent separation of the haplotypes sharing the MT2 determinant on the one hand and the haplotypes sharing the MT3 determinant on the other hand.

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.

Different specificities of an HLA-DRw6 haplotype detected by alloreactive T lymphocytes

DRw6 has been difficult to define serologically. In the present experiments we have developed T cell lines in order to characterize the components of a DRw6 haplotype. This was accomplished by priming T cells with allogeneic mononuclear cells mismatched for DRw6, Dw6, and MT2. Subsequently, three sublines with distinct reactivity patterns were derived by limiting dilution. The specificities detected by these sublines included: (a) a specificity found on a subset of cells positive for DRw6 which was inhibited by monoclonal antibodies against DS(DC), the human homologue of the murine IA-encoded molecules, (b) another DRw6-associated specificity blocked by an MT2-like antibody, and (c) an MT2-like specificity blocked by monoclonal antibodies reactive with a different MT2-associated determinant. These results show that more than one IE-like, as well as the DS/DC (IA-like) molecules, carry distinctive antigenic epitopes that can be recognized by allogeneic T cells. Primed T cell lines may be useful for a better definition of certain haplotypes which are at present difficult to characterize with serological reagents alone.

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.

The use of cellular reagents as an adjunct to typing for HLA-DRw10

Two human T cell lines recognizing DRw10 were generated. One line was directly alloreactive, while a second cloned line recognized mumps virus in the context of a DRw10-like determinant. In panel studies, the lines responded only to DRw10 cells, and not to DR1 (DRw10-) cells. When compared to 5 anti-DRw10 sera, the cellular reagents gave virtually identical results. The generation and use of such cellular reagents may be of particular value for the identification of HLA-D-region specificities that are rare, poorly defined, or for which serologic typing reagents are limited.

Molecular localization of human class II MT2 and MT3 determinants

The specificities of the monoclonal antibodies I-LR2 and 109d6, which recognize MT2- and MT3-like serologic determinants, respectively, have been confirmed by panel testing. In addition, the relationships of these antibodies to other monoclonal antibodies and alloantisera have been studied by means of cell surface fluorescence, complement-dependent cytotoxicity and immunoprecipitation. Using these monoclonal antibodies, molecules encoded by the HLA-D region have been isolated and characterized by amino acid sequencing and peptide mapping. By these criteria, the major populations of molecules bearing MT2- and MT3-like determinants are indistinguishable from DR molecules.

Antigen-specific HLA-restricted human T-cell lines. II. A GAT-specific T-cell line restricted by a determinant carried by an HLA-DQ molecule

Human T-cell lines responsive to the polypeptide antigens GAT and (T,G)-A--L were developed. They were specific for the priming antigens and required the participation of accessory cells matched for HLA-linked determinants, as shown in family studies. In panel studies, the ability of accessory cells to present antigen was shown to be associated with HLA-D-region antigens. However, the specificity of these determinants did not fully correspond to any HLA antigens as currently defined. One GAT-specific subline, derived by limiting dilution, utilized a restriction determinant associated with, but distinct from, the DQw3 (MB3) allospecificity. Blocking studies with mouse monoclonal antibodies indicated that this restriction determinant was carried by HLA-DQ molecules. The epitopes recognized in these molecules appear to be distinct from the alloantigenic determinants currently defined by serology.

Strong association of rheumatoid arthritis with the presence of a polymorphic Ia epitope defined by a monoclonal antibody: comparison with the allodeterminant DR4

Among individuals with rheumatoid arthritis the presence of the polymorphic Ia antigen epitope detected by the monoclonal antibody 109d6 is more strongly correlated with disease susceptibility than are other specificities, such as HLA DR4, DRw53 (MT3) or the antigenic determinant, defined by the monoclonal antibody 17-3-3S. The cells of 93% of Caucasian and Hispanic patients react with the 109d6 reagent. As was the case in normal individuals, all DR4-positive patients express the 109d6 determinant; however, 26% of those with rheumatoid arthritis have the epitope recognized by antibody 109d6, but lack the specificity DR4. Of these, one-third expresses only HLA DR1 and DQw1 (MT1, MB1) determinants. Studies of family members reveal that here the determinants 109d6, DR1, and DQw1 are encoded by the same unusual haplotype. In certain other individuals with rheumatoid arthritis who express DR4, DRw53, and the 109d6 determinants, family studies show that the 109d6 epitope is encoded not only by the haplotype specifying DR4 but also by the opposite haplotype that does not bear the genes for DR4. This suggests that homozygosity for certain Ia epitopes is relevant to determining the disease-susceptibility state. These studies emphasize the utility of monoclonal antibodies as reagents for the recognition of Ia epitopes that are more closely involved in the determination of disease susceptibility than are allomorphic molecules detected by conventional typing alloantisera.