H blood group genotypes and expression of A and 0 antigens in pigs

Tests of over 2000 pigs, with the blood group reagents Ac, Ap and 0, and the reagents Ha, Hb, He, Hd, He and Hc/c, confirmed that the H locus affects the expression of A and 0 antigens. The 'exceptional' phenotypes Ap and — were found in Ha homozygotes of Miniature pigs and in Hcd homozygotes of a semi-inbred Landrace line. They were also found in unrelated pigs of other breeds, and moreover in some individuals with genotypes H ^a H ^cd, H ^ab H ^cd, H-H- and H ^a H ^ab or H ^ab H ^ab.
The mechanism of the effect of the H locus on the A phenotypes may consist in the interaction of certain, not yet completely defined, H genotypes, or in linkage of the H system with the hypothetical ' S ' locus.