The MT3 specificity resides on a novel human class II antigen distinct from the HLA-DR antigen and DC-like antigen

Mapping of the full profile of T cell allorecognition regions on HLA-DR2 beta subunit

Alloreactive human T cell lines were developed by repeated in vitro restimulation with alternate allogeneic cells of similar DR2 serotype, but differing at other HLA loci. These polyclonal T cells recognized DR specificities in common with all DR2 serotypes. The allorecognition profiles of DR2 beta by the T cell lines were mapped by consecutive uniform-sized overlapping peptides encompassing the entire extracellular and intracellular regions of the DR beta subunit. It was found that the T cell allorecognition sites are focused around the first and third polymorphic regions of the N-terminal domain, and interestingly, include conserved areas in the DR beta second domain as well as the intracellular segment beta 222-237. These findings have important implications for allorecognition. Comparison with the previous analysis of antibody-binding regions of DR2 beta revealed some similarities and differences in the antibody and T cell alloresponses to this histocompatibility antigen.

Protein analysis of HLA-DR2.3 haplotype

The human major histocompatibility antigens (HLA-DR, HLA-DQ, and HLA-DP), consisting of alpha and beta chains, show extensive polymorphism. Based on differences of T-cell responses, the serologically defined DR2 specificity has been divided into Dw2, Dw12, and several putative additional "Dw subtype" specificities (AZH, FJO, and MN2, which we shall designate as "DR2.3", and LD-5a). To investigate the relationships of these specificities, DR and DQ molecules were analyzed by two-dimensional gel electrophoresis (2D-PAGE). The 2D-PAGE patterns of the DR molecules are identical among DR2.3 cells. Three DR beta chain polypeptides are expressed on DR2.3 cells. The electrophoretic mobilities of two of these beta chains are different from those of beta chains from the Dw2 and Dw12 cells. The DR molecules of the LD-5a cells show similar 2D-PAGE patterns with those of DR2.3 cells. The 2D-PAGE patterns of DQ molecules are identical among DR2.3 cells. The electrophoretic mobilities of DQ beta chains are different for Dw2, Dw12, LD-5a, and DR2.3 cells. These results indicate that the AZH, FJO, and MN2 cells have identical or very similar DR and DQ molecules and constitute a third, and relatively homogeneous, subgroup ("DR2.3") of the DR2 specificity. In addition, DR2.3 cells have a unique characteristic in that they express three DR beta chains.

A novel HLA class II alloantigen detected by an alloantiserum TK2

An alloantiserum, TK2, obtained from a kidney transplant patient, was investigated. TK2 reacted with B lymphocytes that had only one detectable DQ antigen. DQ "blank" homozygous cell lines were positive for TK2, but DQwl, DQw2, and DQw3 homozygous cell lines failed to react with TK2. Positive reactions for TK2 segregated with DQ "blank" haplotypes in the families studied. The reactivity of TK2 to B lymphocytes was strong, while its reactivity to monocytes was very weak. When TK2 was absorbed with DQ "blank" cells, it became unreactive to other lymphocytes. TK2 blocked the binding of an anti-DQ monoclonal antibody to DQ "blank" cells. It did not affect the binding of the antibody to DQw1 and DQw3 cells, nor did it affect the binding of an anti-DR monoclonal antibody to a DQ "blank" cell line. These findings suggest that TK2 can detect a new HLA class II alloantigen that corresponds to a DQ "blank" specificity.

A possible split of antigen DQw1 identified by antiserum T3516

One of the human class II antigens DQw1, which was officially recognized at the 9th International Histocompatibility Workshop in 1984, has a comparatively broad spectrum. One multiparous woman's serum was confirmed to have an antibody which shows a reaction pattern of short DQw1 or a split of DQw1. Our analysis was performed with a population study, two-dimensional gel electrophoresis and blocking experiment by monoclonal antibodies.

Sequence polymorphism of HLA DR beta 1 alleles relating to T-cell-recognized determinants

HLA class II molecules are a highly polymorphic family of dimeric cell-surface proteins primarily involved in regulating T-cell responses to extrinsic antigens. To define regions of class II molecules involved in T-cell recognition, we have now compared sequences of three HLA DR beta cDNA clones obtained from cells that all express the same serologically defined determinants but differ in terms of T-cell-recognized specificities. The comparisons indicate that very few (one to four) nucleotides differ between what are almost certainly alleles of the DR beta 1 locus. All differences were in the first domain of the molecule and all localized to a region from amino acids 71-86. Because all differences were found only in this region of the molecule, and because DR alpha-chains seem to be relatively non-polymorphic, these positions in the DR beta-chain must have a major role in influencing T-cell recognition of the DR molecule.

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.