Allelic exclusion of M1 (IgM) allotype on the surface of chicken B cells

The membrane expression of M1 (IgM) and G1 (IgG) allotype markers on peripheral blood lymphocytes was examined by immunofluorescence. In homozygous chickens 15% lymphocytes stained with either anti-M1 or with polyspecific rabbit anti-Ig serum, suggesting that M1 is expressed on the surface of probably all B lymphocytes. In heterozygous M1a/M1b individuals antisera against either allelic antigens reacted with 50% of the total surface Ig positive cells as evidence for the allelic exclusion of surface M1 expression. Donor allotype synthesis was determined from serum allotype levels in congenic cyclophosphamide-treated recipients of lymphoid cells. Treatment of cells with anti-M1 serum prior to transfer inhibited both M1 and G1 allotype synthesis. The treatment of heterozygous (M1a/M1b, G1a/G1e) cells with anti-M1b serum inhibited specifically the synthesis of M1b and G1e allotypes controlled by linked genes from the same parental chromosome. Thus, B cells which had been the targets for anti-M1 antibody mediated suppression are also subject to allelic exclusion.