Primary structural sequence polymorphism in the human class II MHC antigen 33.1

Characterization of a human T cell line reactive to a 52 kDa islet protein

A 52 kDa islet protein has recently been identified as the target of autoantibodies in the NOD mouse model of IDDM and humans with IDDM. However, the presence of T cell immunity against the 52 kDa islet protein in IDDM has not been reported. We report the establishment and characterization of a T cell line (19KW) that reacts to purified 52 kDa islet protein (purified p52) from a subject with IDDM. The purified p52 induced a proliferative response as measured by thymidine incorporation in the 19KW T cell line with a stimulating index of up to 48. The proliferative responses were greater with increasing doses of purified p52 (0.1, 0.5, 2.0, and 6.0 microg/well). No reactivity was found to a liver fraction purified in the same manner as 52 kDa protein, BSA, ovalbumin, extracts of rat muscle, fibroblast, adrenal, or pituitary tissue and to a rat exocrine cell tumor. Irradiated PBMC were required as antigen presenting cells (APC) for 19KW reactivity to the purified p52. The addition of anti-HLA DR or anti-HLA DQ antibodies significantly decreased the islet antigen-induced proliferative response. The addition of antibodies to HLA DP and class I MHC had no effect. Flow cytometric analysis revealed that the majority of T cells expressed CD4 and CD45RO molecules. T cell receptors Vbeta6 and Vbeta5.1 were found on 30 and 14% of the CD3+ (T cells) 19KW cells, respectively. In conclusion, a purified p52-reactive human T cell line predominantly consisting of TCR Vbeta6+ and Vbeta5.1+ cells has been established from a subject with IDDM. Reactivity to the purified p52 is antigen dose-dependent, tissue specific, requires irradiated PBMC as antigen presenting cells, and is HLA DR- and HLA DQ-restricted. T cell lines specifically reactive to p52 may be useful for investigating further the role of this antigen in the pathogenesis of IDDM.

Intracellular events associated with inhibition of B cell activation by monoclonal antibodies to HLA class II antigens

We have investigated several aspects of the inhibitory effects of monoclonal antibodies (mAb) directed against MHC class II antigens in B cell activation/proliferation, using a panel of mAb specifically reactive with antigens encoded by HLA class II loci (DP, DQ, DR). All mAb except the anti-DP mAb inhibited significantly anti-mu plus B cell growth factor-induced DNA synthesis. Only one mAb, however, which was reactive with gene products of all three class II loci (DP, DQ, DR) inhibited anti-mu-induced DNA synthesis as well as c-myc mRNA expression. In addition, the same mAb inhibited the early events induced by anti-mu stimulation alone, including phosphatidylinositol turnover and elevation of [Ca2+]i. In contrast to previous findings in the murine system, none of the anti-MHC class II mAb used in this study increased the cAMP levels.

Partial amino acid sequence analysis of rabbit MHC class II molecules isolated from two-dimensional polyacrylamide gels

Partial N-terminal amino acid sequence analyses were performed on rabbit MHC class II molecules eluted from 2-D electrophoretic gels. Rabbit spleen cells were biosynthetically labelled with 3H-phenylalanine, 3H-tyrosine and 35S-methionine and class II molecules were immunoprecipitated with a monoclonal antibody, 2C4. The immunoprecipitates were electrophoresed on 2-D gels and as many as 15 spots were observed. Individual spots corresponding to alpha and beta chains were eluted from unfixed gels following visualization of the spots by autoradiography of 35S-Met labelled polypeptides. Ten eluted polypeptides were subjected to amino acid sequence analysis to locate Phe and Tyr residues. Comparison of these partial sequences with sequences of human class II molecules indicated that each of six beta chains and three of four alpha chains were homologous to human DQ molecules; one of the alpha chains appeared homologous to DR alpha or DP alpha. The assignment of alpha or beta chain to the polypeptides was confirmed by radiosequence of molecules labelled with 35S-Cys residues. Thus, by a relatively simple procedure, individual MHC class II polypeptides in spleen cell lysates have been separated from each other and partial amino acid sequences have been obtained.

Nonrandom association of cellular antigens with HTLV-III virions

Retroviruses are known to incorporate cellular antigens as they bud from infected cells. To identify the cellular antigens that associate with the AIDS-retrovirus, we evaluated a preparation of HTLV-III antigens with a panel of monoclonal antibodies reactive with a variety of antigens expressed on the H9 T-cell line used to produce the virus. Only monoclonal antibodies that identified HLA class-II antigens, beta-2 microglobulin, and a single anti-HLA class-I antibody were reactive in an ELISA of solubilized HTLV-III virus. No reactivity was seen with 11 monoclonal antibodies to T-cell antigens or with five antibodies to determinants on HLA class-I A or B molecules. These data suggest that on H9 cells the association of budding HTLV-III virions with cellular antigens may be a nonrandom process in which some HLA antigens, particularly class-II antigens, are selectively incorporated into the viral envelope. It is possible that a selective association of HLA class II antigens with budding HTLV-III virions may also occur for T cells infected in vivo, and could have relevance for the pathogenesis of this virus.

Multiple epitopes on a single DQ molecule from the DQw3-carrying haplotypes

Multiple polymorphisms on the DQ molecule(s) have been detected by monoclonal antibodies (MoAbs). Among these, TA10 and IIB3 have been described as two new alleles in the DQ region other than the conventional DQw1-w3 allelism. The TA10 specificity is DQw3-related and is in linkage disequilibrium with DR5 and weakly associated with DR4. The IIB3 specificity is DQw1-related and is in linkage disequilibrium with DR2, DR4, DRw9 and DRw13. Thus, the DQw3-carrying haplotypes are either positive with TA10 or IIB3. The molecular and topological analysis has revealed that both TA10 and IIB3 determinants were expressed on a single DQ molecule that also carried the DQw3 determinants on DR5 and DR4 cell lines, respectively. Thus, a single DQ molecule generated multiple epitopes detected by alloantisera and/or MoAbs at least on the DQw3-carrying haplotypes. These would be useful for unraveling the largely unknown functions of the DQ class II molecules.

A new polymorphic determinant on HLA-DQ molecules

In man, the immune response genes are located within the HLA-D/DR region, and the gene products, the Ia antigens, are expressed on B lymphocytes, monocytes, and a percentage of null cells and activated T lymphocytes. We recently identified a human Ia antigen, K19, which appeared to be limited in its expression to B lymphocytes, and to be preferentially expressed on the more mature cells within this population. This work was facilitated by a monoclonal antibody. HK-19, which recognized a monomorphic determinant of this Ia molecule. We now report the characterization of a second monoclonal antibody, HK-13, which recognized the same molecule as HK-19, but only on cells from some individuals. The greater affinity of HK-13 allowed more complete characterization of the K19/K13 molecule. This characterization included cytofluorography, two-dimensional gel electrophoresis, tryptic peptide mapping, and partial N-terminal amino acid sequencing, and indicated that K19 and K13 were epitopes on HLA-DQ (DC) molecules. The pattern of reactivity of HK-13 on a panel of typing cells did not correlate with any of the known HLA-DQ polymorphic determinants. Thus, HK-13 is a new polymorphic determinant of the HLA-DQ series.

Cells homozygous for two HLA-DR7-associated HLA-D specificities express highly similar DR molecules but different DQ molecules

The Ia molecules expressed by cells homozygous for two distinct HLA-DR7-associated HLA-D specificities, Dw7S and Dw11L, were compared. The complete Ia phenotypes of these cells are DR7, DRw53, DQw2, Dw7S, DPw4 and DR7, DRw53, DQw3, Dw11L, DPw4, respectively. Immunofluorescence analysis revealed that three DQ-specific monoclonal antibodies (Leu-10, 33.1, and HK-19), which detect polymorphic DQ determinants that do not correspond to known serologic specificities, are nonreactive with DR7, Dw7S cells but are reactive with DR7, Dw11L cells. The DR molecules isolated from Dw7S and Dw11L cells are very similar and comigrate when analyzed together by two-dimensional gel electrophoresis. In contrast, the DQ molecules isolated from these cells are structurally distinct: the DQ beta chains of DQw2-bearing molecules from Dw7S cells are very basic, while those of DQw3-bearing DQ molecules from Dw11L cells are more acidic. The finding that two DR7, D-different cells express indistinguishable DR molecules and structurally distinct DQ molecules documents a unique pattern of Ia molecular organization which is different from those previously described for the DR2-, DR4-, or DRw8-associated HLA-D specificities.

Gene organization of DC and DX subregions of the human major histocompatibility complex

The DC and DX subregions of the human major histocompatibility complex (MHC) have been cloned from a cosmid library made from a human B-cell line, Priess. The DC subregion, 48 kilobases, includes the DC alpha and DC beta genes. A second DC-like region, the DX subregion, 35 kilobases, contains the DX alpha gene and a newly found beta gene termed DX beta. Since the DC and DX genes are highly homologous in nucleotide sequence, gene size, exon-intron organization, and direction of transcription, the DC and DX subregions were presumably generated by duplication of an ancestral alpha-beta gene pair. Nucleotide sequencing indicates that all four genes have intact coding sequences and promoter regions. Homology between the upstream promoter sequences of these four genes and seven other class II genes at nucleotides -69 to -78 and -98 to -110 highlights these previously described conserved elements. Moreover, a striking conservation of flanking alpha-gene-specific and beta-gene-specific sequences has been observed. Comparison of Southern blots of Priess DNA with DC alpha and DC beta cDNA probes with isolated cosmid clones showed that (i) the human chromosome encodes only two DC alpha-related and two DC beta-related genes, namely, DC alpha, DX alpha, DC beta, and DX beta, and (ii) the DC and DX subregions are homozygous in Priess cells.

Cellular distribution of a human I-A-like (DS/DC) antigen on normal and neoplastic lymphoid cells

Previous biochemical studies have shown that B cell specific, monoclonal antibody, McAb 33.1, reacts with a class II antigen that represents a human analogue of murine I-A (DS/DC) antigens (J. Exp. Med. 158:1924, 1983). McAb 33.1 recognizes a polymorphic human B lymphocyte specific antigen present on mu+, B1+ peripheral B cells, B lymphoid cell lines, activated B cells, and neoplastic B lymphoid cells. Of 100 HLA-D/DR typed EBV-transformed lymphoblastoid cell lines tested, only those from DR3,3 and DR7,7 individuals failed to react with McAb 33.1. The 33.1 antigen is present at lower concentrations on B cells from blood, tonsil, spleen, and lymph node when compared to B cell lines. By contrast, the antigen is not detectable on blood T lymphocytes, T cell lines, or mitogen activated T cells and it is absent on monocytes of some individuals or is present only on a minor subpopulation (approximately 20%). McAb 33.1 should facilitate the functional, structure, and molecular dissection of the human Ia system.

Identification of two cis-encoded HLA-DQ molecules that carry distinct alloantigenic specificities

The monoclonal antibodies Genox 3.53, S1, and R1 define polymorphic epitopes localized to DQ molecules. All three antibodies showed a strong association with the HLA-DR antigens 1, 2, and w6 when tested on a panel of 68 unrelated individuals, suggesting that they all recognized the DQw1 allospecificity. However, segregation analysis and binding studies with a panel of HLA-D/DR homozygous cells indicated that these monoclonal antibodies defined two different alloantigens. Cells homozygous for DR 1, 2, or w6 expressed the epitopes defined by all three antibodies (i.e., S1, R1, and Ge) while cells homozygous for DR4 and DRw8 expressed only the S1 and R1 epitopes. Sequential immunoprecipitation analyses in S1+/R1+/Ge+ individuals, in which the three epitopes were shown by segregation analysis to be encoded by the same chromosome, revealed two distinct DQ-like molecules. While R1 and S1 appeared to reside on the same molecule, the epitope defined by Genox 3.53 was on a different molecule. Identical results were obtained with DR1-, DR2-, or DRw6-bearing cells. Thus it appears that DQw1-bearing individuals express two cis-encoded DQ-like molecules that carry distinct alloantigenic specificities.