“…A n even more significant linkage disequilibrium has been shown between the C2" and HLA-D loci (33,34), with C2" and HLA-B tentatively mapped on opposite sides of HLA-D (35)(36)(37). Histocompatibility genes have also been linked with those controlling synthesis of factor B (36)(37)(38). The levels of factor B in patient Vi T and his 8 immediate relatives, however, showed no apparent relationship to C or HLA phenotypes or inheritance; rather, the results of these and other studies of factor B levels in C2D homo-and heterozygotes ( I , 6, 8, 12, 39) would seem to indicate an acquired, instead of inborn, basis for the decreases observed.…”