Complexities of the <i>MN</i> Locus

Abstract

Summary Fifteen examples of rare alleles of M and N were found in serial tests on 3,895 blood donors. They include: (1) a third example of M c , which differs from the two previously known ones in that it is inherited as a M c S (instead of M c s ) gene complex; (2) an example each of two genes whose phenotypic expression consists of the antigens M, N and St a (Stones), but which differ so markedly, particularly as to the ‘amount’ of N formed, that they have been given separate symbols, namely, M z and M r ; (3) an example of N 2 , a gene defined as giving rise to N, in a form weaker than ‘normal’, but not to any M antigen. The antigens arising from each of these four genes were studied in detail, by means of parallel tests with large panels of M and N reagents on blood samples from persons found in the 3,895 series, selected members of their families, and unrelated carriers of M c , M r , and N 2 . Also included in these studies were cell samples heterozygous for M g and M k , and ‘special’ sera such as anti‐ M g , anti‐ M k , anti‐ M ’, etc. Anti‐ M ’ subdivides groups M and MN in much the same way as anti‐M 1 does; in one respect at least, however, it differs clearly from the latter, namely, in its reactions with NM c and NM z cells. The results of tests with anti‐M k on cells of all available MNSs genotypes suggest the possibility that M k is a precursor substance of the MNSs system.