Complementary DNA (cDNA) clones encoding (3 chains of the DR and DQ regions and a chains of the DQ region were isolated and sequenced from four homozygous DR4 cell lines of different HLA-D types: GM3103(Dw4), FS(DwlO), BIN40(Dw14), and KT3(Dwl5). When compared with each other and with a previously published sequence from a DR4 (Dw13 cell line), the variability of DR(3I gene products is generally restricted to the region around amino acid position 70, with an additional polymorphism at position 86. Many of these differences, including an unusual amino acid substitution at position 57 in the Japanese cell line KT3(Dwl5), may be due to gene conversion events from the DR(32 or DXI3 genes. In contrast, DR132 molecules are identical in Dw15, Dw1O, and Dw4 cell lines. DQj3 chains isolated from GM3103(Dw4), FS(DwlO), and BIN40(Dw14) are also identical. However, the DQB sequence from cell line KT3(Dwl5) differs substantially from all other previously reported DQB alleles, consistent with its serological designation, DQ "blank." The first domain sequences of DQa chains were identical in all four cell lines. The data suggest that relatively circumscribed amino acid changes in the DRB1 molecule are responsible for the HLA-D typing differences between some haplotypes.The class II molecules of the human major histocompatibility complex exhibit extensive polymorphism detected in both serologic (DR typing) and mixed lymphocyte culture (Dw typing) reactions; these reactions are considered to reflect the function ofthese molecules in regulating immune responsiveness and in determining both disease susceptibility and graft rejection. Biochemical analysis has shown that class II gene products are expressed at the cell surface as heterodimers of a and A3 chains encoded by genes present in three subregions-DR, DQ, and DP (1). Within the DR subregion, one a-and three /-chain genes have been described; the a-chain gene and two (3-chain genes, DR/31 and DR/32, are clearly expressed (2). The DQ subregion contains two sets of a-and /-chain genes, DX and DQ a and ( (2); however, it is unclear whether the DX genes are expressed (3). With the exception ofDRa, all ofthe expressed genes display considerable allelic diversity. Genes of the DR and DQ subregions tend to form stable haplotypes in the population; thus, at least four polymorphic loci, DR/31, DR(32, DQa, and DQ/3, may contribute to the classical DR and Dw typing reactions.Among haplotypes that type serologically as DR4, several subtypes (HLA-D types) have been defined on the basis of T-cell responses in mixed lymphocyte cultures. These have been designated Dw4, DwlO, Dw13, Dw14, and Dw15 (4). Although 13 chains from individuals ofdifferent DR type differ dramatically in their amino acid sequence, very little is known about sequence polymorphism among such closely related haplotypes. We have sequenced a-and ,B-chain cDNA clones isolated from homozygous DR4 cell lines of differing HLA-D type. This has allowed us to delineate polymorphisms that appear to be responsible for the H...

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Objective. To examine the effects of nitric oxide (NO) and its more stable derivative, S-nitrosoglutathione (SNO-GSH), on the response of activated T lymphocytes.Methods. The effects of NO and SNO-GSH on DNA synthesis, interleukin-2 (IL-2) production, IL-2 receptor expression, and cGMP accumulation were determined in phytohemagglutinin-activated peripheral blood mononuclear cells (PBMC) and spleen T cells. Results. Nitric oxide (half-life [T,,,] < 15 seconds)did not inhibit T cell proliferation. However, the derivative SNO-GSH (25 ErM) (TI,, >2 hours) inhibited DNA synthesis by a mean 2 SD of 65 2 19.6% (P < 0.001) in PBMC and 75 f 15% (P < 0.001) in spleen cells.Macrophage depletion of PBMC did not abrogate the inhibition. SNO-GSH had no effect on IL-2 production or IL-2 receptor expression. NO (25 ptf) increased the cGMP content of PBMC (0.65 f 0.15 pmoles/106 cells; P < 0.04), as did SNO-GSH (25 ptf) in both PBMC (3.8 2 1; P < 0.001) and spleen T cells (5.2 f 1.2; P < 0.001). Methylene blue and hemoglobin, which are NO inhibitors, inhibited SNO-GSH-induced cGMP accumulation (P < 0.001).Conclusion. SNO-GSH inhibits T cell DNA synthesis independently of IL-2 production and in associa-

Ia antigens were strongly expressed on a considerable proportion of cells eluted from the damaged articular cartilages of certain individuals with osteoarthritis, rheumatoid arthritis, traumatic arthritis, or from osteochondromas. In contrast, Ia antigens were found on less than 1% of cells eluted from the more normal appearing cartilage of certain other patients with osteoarthritis, rheumatoid arthritis, osteonecrosis, femoral neck fractures, an enchondroma, and a chondrosarcoma. The cell preparations obtained from these latter individuals consisted of clusters of 1-4 chondrocytes embedded in a surrounding island of the pericellular matrix, whereas as in the samples that yielded Iapositive cells, many chondrocytes were isolated as free cells without a surrounding matrix. The Ia antigens were detected primarily on this latter cell population, suggesting that their expression might indicate a chondrocyte activated to alter its surrounding matrix. The cytologic features of the Ia-positive cells were indistin- guishable from those of the Ia-negative chondrocytes. All eluted cells lacked antigens of the monocyte, B cell, or T cell lineages. An antigen detected by the monoclonal reagent M+R-17 was identified on the membrane of large numbers of chondrocytes, both with and without the pericellular matrix, indicating that the matrix in these preparations was permeable to molecules the size of antibodies. A monoclonal antibody 83c2, demonstrated to react with an 85-kD surface molecule expressed on certain fibroblastoid and other cells, detected an antigen present on the majority of normal chondrocytes and in varying percentages of cartilage cells obtained from patients with osteoarthritis or rheumatoid arthritis. Of special interest, the periphery of the pericellular matrix was stained by this reagent in an irregularly distributed ring-like zone, suggesting that the 83c2 molecule was shed into the matrix from the cell surface and accumulated in these areas.The articular cartilage is a highly specialized tissue characterized by a relatively small number of cells embedded in an avascular extracellular matrix produced and maintained by the chondrocytes (I). The chondrocytes are usually found in clusters of several cells in a specialized region of the ground substance, the lacunar or pericellular matrix (1).Degenerative and inflammatory joint diseases are characterized by the loss of articular cartilage reflecting the operation of a variety of mechanisms including metabolic and mechanical factors, the destruction caused by enzymes released from synovial cells upon direct cell contact with the cartilage surface (2), and the release of mediators stimulating the chondrocytes to actively resorb their own matrix (2-5).