HL-A ANTIGENS AND GENES .2. STUDIES OF ANTIGEN MH (=HL-A5) OF 4 SUB-LOCUS

Summary. To study the relations between the antigens MH and PA 4C, 297 unrelated Norwegians and 30 selected families were examined. Association analysis showed a complete inclusion of MH in the antigen 4C. This could be explained by the 4C serum containing two antibodies of different specificity, anti‐MH and anti‐X, which was supported by absorption experiments. Family studies showed that the supposed genetic determinants for MH and X were inherited in a Mendelian way, and population studies suggested that the two genes might be alleles at the 4 sub‐locus. One family further supported this concept. It was also found that MH is probably identical to the antigen designated HL‐A5, and by skin grafting within an MH incompatible donor‐recipient pair it was possible to reproduce antibodies of this specificity. This shows that HL‐A5 is a separate and well‐defined transplantation antigen of the HL‐A system. © 1969 Blackwell Publishing Ltd