M₁, a Subdivision of the Human Blood-Group Antigen M

Abstract

A ‘NEW’ antibody, anti-M₁, has been found as a component in six out of twenty available human anti-M sera : in one of them practically all the antibody was anti-M₁. No anti-M₁ could be detected in anti-M sera from eight rabbits and from one horse, nor in an extract of the seeds of Iberis amara (which contains anti-M) : nor could it be found in a wide range of other antisera. We are calling the antibody anti-M₁, because in several ways it behaves like anti-A₁ of the ABO system and anti-P₁ of the P system.