B- and T-cell-specific alloantigens in man.

Screening for B-cell-specific antibodies in unabsorbed pregnancy sera preselected for weak reactivity in regular HLA-A, -B, and -C screening yielded a relatively high proportion (35/81) of B-cell-specific antibodies. Most B-cell-specific antibodies react broadly, showing inclusion phenomena suggesting 'cross-reactivity' analogous to that observed in HLA-A and -B serology. In control experiments with T-cell-enriched suspensions three antisera reacted with T cells and not with B cells. These antisera are highly associated with HLA-A2 in the unrelated population and segregate with HLA haplotypes in families and with HLA-A in a family with HLA-A, B recombination, Thus it appears that the human equivalents of Ia antigens may include--in analogy to the murine Ia antigens--B cell- as well as T-cell-specific alloantigens.