High frequencies of B8, DR3 and C4A null alleles and immunological disorders in a family of four generations.

In a Finnish family covering four generations many members had immunological symptoms or disorders (mostly skin or joint oriented) with the presence of the B8 antigen positive Major Histocompatibility Complex (MHC) haplotype. Immunological parameters including the presence of autoantibodies, quantitative analysis of the complement components C4, Factor B (BF) and C3 and the serum capacity to inhibit immune precipitation were investigated in relation to the genetic MHC markers. The results showed the importance of the high frequency of the C4A null alleles to these disorders.