A reanalysis of the HLA-B7 cross-reactive group.

Cross-reactivity between antigens of the HLA-B7 cross-reactive group (B7 CREG) was investigated by the serological analysis of 60 "broad" cytotoxic HLA antisera produces by pregnancy alone, the HLA typing of the antiserum donors and the identification of their immunizing antigens. Thirty-five sera, made in response to B7, covered (as a group) HLA-B7, B27, Bw42, Bw48, Bw54, Bw55, Bw56, Bw60 and Bw61--the B7 CREG antigens. Bidirectional cross-reactivity occurred between the B7 antigen and B27, Bw55, Bw56 and Bw60 antigens but not between the major B7 CREG antigens B27, Bw22 and B40. HLA-B27 stimulated antisera included B7, B13 and Bw47 within their reaction range and Bw55/Bw56 cross-reacted with Bw42, Bw54, Bw57, Bw58, Bw62 and Bw63. Bidirectional cross-reactivity was observed between Bw55 and Bw57. Fourteen responders possessed an antigen cross-reactive with their immunizing antigen. These findings are discussed in relation to the sharing of determinants by pairs and "families" of HLA antigens.