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The HLA-CW2 antigen of the B lymphoblastoid cell line BRI 8 is structurally homologous to the HLA-A and B antigens as judged by various criteria. Each antigen comprised a glycosylated polypeptide of 43 000 molecular weight that is noncovalently associated with beta2-microglobulin (beta2m). Some small differences in molecular parameters were, however, revealed. Thus, the deoxycholate-solubilized HLA-CW2 antigen sedimented at the same rate as the HLA-A antigens but at a slightly faster rate than the HLA-B antigens. This variation is apparently is apparently due to different amounts of bound deoxycholate. Also, whereas essentially all of the HLA-A and B antigens and about half of the HLA-CW2 antigen were adsorbed strongly by Lens culinaris lectin-Sepharose, the remaining HLA-CW2 antigen was bound much more weakly and did not require sugar for elution. This difference reflects some structural heterogeneity in the carbohydrate moiety of the HLA-CW2 antigen. The results of various studies suggest that the HLA-CW2 antigen is expressed to a lower extent than the HLA-A or B antigens and that essentially all of the beta2m of the BRI 8 plasma membrane is associated with the HLA-A, B and C alloantigenic polypeptides.

As judged by indirect immunofluorescence, phorbol 12,13-dibutyrate and 1.oleoyl-2-acetylglycerol induced a rapid, concentration-dependent decrease of about 50% in the surface expression of the T3 antigen on human T lymphoblasts, and of T3 and the T-cell antigen receptor on HPB-ALL cells. Direct binding experiments using 'MI labeled antibody indicated that the reduction in T3 expression corresponded to a decrease in the number of antigen molecules rather than a change in their affinity. (5), and mutant cell lines selected for lack of expression of T3 also showed loss of Ti and vice versa (16). Down-regulation of the T3/Ti complex induced by specific antigen has been correlated with an inhibition of antigen recognition and related immune functions (2, 17, 18). However, despite its apparent critical role in regulating Tlymphocyte responses, the molecular basis of the regulation of the surface expression of T3 and Ti is poorly defined. Recent results suggest that phorbol esters can modulate the expression of various T-cell surface determinants (including T3), induce antigen unresponsiveness in specific T-cell clones, and stimulate some of the biochemical steps leading to T-cell activation (19-21 (27). The UCHT1, W6/32, and RFT11 antibodies were purified from ascitic fluid by ammonium sulfate precipitation and staphylococcal protein A-Sepharose affinity chromatography. The H1-2D4 antibody was used as ascitic fluid. 125I-labeled UCHT1 (1.4 x 108 cpm/nmol) was prepared by using the Enzymobead (Bio-Rad) modification of the lactoperoxidase-catalyzed iodination technique. Fluorescein-labeled and unlabeled rabbit antibodies against mouse immunoglobulin were purchased from Dakopatts (Mercia Brocades, Weybridge, Surrey, England). Endo-/3-N-acetylglycosaminidase F (Endo-F) was purchased from New England Nuclear. Purified recombinant human interleukin 2 was donated by K. A. Smith (Dartmouth Medical School, New Hampshire). Human peripheral blood mononuclear cells were separated from fresh blood by Ficoll-Hypaque discontinuous gradient centrifugation.Cell Cultures. The human T leukemia cell line HPB-ALL was cultured in RPMI 1640 medium containing penicillin (100 units/ml), streptomycin (50 ug/ml), and 10o (vol/vol) fetal calf serum (Flow Laboratories). Human T lymphoblasts were prepared by stimulating peripheral blood mononuclear cells (106 cells per ml of RPMI 1640/10% fetal calf serum) with UCHT1 antibody (250 ng/ml) for 72 hr. The cells were washed to remove UCHT1 and growth was maintained at concentrations of 105_106 cells per ml for up to 10 days by supplementing every 2 days with 0.1 nM interleukin 2. For modulation studies, cells were washed three times in RPMI Abbreviations: Ti, T-cell antigen receptor; PBt2, phorbol 12,13-dibutyrate; OleAcGro, 1-oleoyl-2-acetylglycerol; Endo-F, endo-3-N-acetylglycosaminidase F. 8158The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indica...

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