B-cell alloantigens in two recombinant families: prediction of a B/D recombination using B-cell-specific alloantisera.

During the VIIth Histocompatibility Workshop, 44 sera were selected that defined B-cell alloantigens showing correlation with the HLA--D antigenic determinants. The segregation of these antigens, now called DRw (HLA--D-related), was studied in a family that contained one HLA--A/B recombinant and one HLA--B/D recombinant sibling. It could be established that the DRw-1 antigenic determinants segregated with the B-D region in the A/B recombinant sibling and that the DRw-2 antigen segregated with the D region of the B/D recombinant child. In the second family, DRw typing segregated with the D region of the B/D recombinant child. In the second family, DRw typing showed that one of the children was identical with an HLA--ABC non-identical sibling. This suggested that a crossing-over had occurred. This was confirmed by mutual non-stimulation of these HLA--ABC non-identical children in the mixed lymphocyte culture. This crossing-over involved the DRw-3 alloantigen. These data confirm the assumption that serologically defined B-cell alloantigens are coded for by genes located outside the HLA--A/B region on the B-D side of chromosome. Moreover, these data suggest that, within families, serological B-cell genotype identity can predict a mutual unresponsiveness in the lymphocyte culture. However, findings in these two families indicate that discrepancies nevertheless exist between B-cell serology and mixed lymphocyte reactions and that mutual stimulation can occur despite apparent identity of serological B-cell phenotype and that B-cell phenotype identity does not necessarily predict mutual unresponsiveness in the mixed lymphocyte culture.