Characterization of three new apparently related high frequency antigens

Three high frequency reactive antisera (Kir, Oca, Mil) are described which, based on serologic and genetic characteristics, identify a set of apparently related antigens. The antibodies react only by indirect antiglobulin technique against both adult and cord red blood cells, are primarily IgG, are not complement dependent nor enhanced by papain pretreatment of red blood cells, are high titered but of low avidity, and are not neutralized by serum nor absorbed by platelets. The antisera are not identical with, but may be related to, the Kna antibody. Population data show reactivity frequencies of 99.8 per cent for Kir, 98.7 per cent for Oca, and 96.4 per cent for Mil. The four phenotypes found are Kir+, Oca+, Mil+; Kir+, Oca+, Mil- Kir+, Oca-, Mil+ and Kir-, Oca-, Mil-. The occurrence of five unrelated triple negative individuals is greater than would be expected by chance alone for three independent antigens. Family studies demonstrate that the triple negative phenotype appears to be a recessive trait not linked to the Fy or MNS loci, and the Mil-trait is not linked to ABO, Jk, or HLA. Clinical observations following infusion of incompatible blood and in vivo survival studies of 51Cr tagged red blood cells indicate that the antigens, though potent immunogens, are not clinically significant.