Third HL-A segregant series: genetic analysis and molecular independence on lymphocyte surface

Five sera which detect two alleles of the third HL-A locus (T2 and T4) are described. Statistical analysis of a panel of 220 donors gave gene frequencies in a French Parisian population which are comparable to the results of Scandinavian authors. Segregation observed in 50 families emphasized the linkage disequilibrium with SD2 alleles. T1 was found to be associated with one part of W22 (Da30) and T3 with the other part non-Da30). No recombination was observed between SD2 and SD3, and the distance between these two loci can be estimated at less than 0.0042 U. Differential capping experiments showed that redistribution of SD3 antigens did not affect the SD2 or SD1 products, indicating that they are borne on the cell surface by independent structures. Moreover, capping of SD1, SD2 and SD3 antigens did not provoke complete redistribution of beta2microglobulin which suggests that not all beta2M molecules are linked to HL-A antigens.