Use of a Monoclonal Antibody (W6/32) in Structural Studies of HLA-A,B,C Antigens

Abstract

The experiments reported here show that W6/32 antigenic activity is retained in papain-solubilized HLA antigens and that the W6/32 antibody provides a useful standard reagent to detect and assay HLA-A,B,C antigens. The W6/32 antibody was purified and used to construct an immunoaffinity column. Soluble HLA-A,B,C antigens from papain or detergent-treated membranes could be highly purified in a single step with this column and serologic analysis showed that HLA-A,B and C antigens were bound to the column. Thus, the W6/32 antigenic determinant is present on gene products of all three loci. The amount of HLA-A,B,C antigens on the surface of human B cell lines and peripheral blood lymphocytes was measured with W6/32 antibody. B cell lines expressed, on average, 9 times as much cell surface HLA-A,B,C antigens as peripheral lymphocytes, although there was appreciable variation within each group. The B cell line Bri 8, for example, expressed 1.5 × 106 W6/32 antigenic sites, and by inference, HLA-A,B,C molecules per cell. Equal amounts of β2m and HLA-A,B,C chain were found on both cell types. The isolated HLA-A chain from intact 125I-HLA-A2 antigens weakly bound to W6/32 antibody in contrast to 125I-β2-microglobulin (β2m) isolated from the same preparation of HLA-A2 antigens that showed no demonstrable binding. when an excess of cold β2m was added to the isolated 125I-HLA-A2 chain, the binding to W6/32 antibody was considerably enhanced. These results suggest that the W6/32 antigenic determinant involves only amino acids of the HLA-A,B,C chain and is a product of their three dimensional configuration. Stable maintenance of this configuration appears to be dependent on the association of the HLA-A,B,C chain with β2m.