The porcine M blood group system: evidence to suggest assignment of its M1 factor to a new system (P).

A new allele Maejm and a more precise genetic analysis of the Ml factor previously assigned to the M system are described after screening three generation families (Wild Boar x Pietrain, Meishan x Pietrain) for the M blood group system using a complete set of 13 M reagents. From informative families with proven parental M genotypes it was shown that the Ml antigen is controlled by an allele from another system. We propose to designate this new system P and to change the factor designation from Ml to Pa.