The serology of the York-Cost-McCoy-Knops red blood cell system.

Since 1965, sera from 305 patients who produced alloantibodies against the red blood cell antigens Yka, Csa, McCa, McCc, McCd and Kna have been evaluated by the author. These antibodies were acquired as a result of either transfusion or pregnancy. They reacted only by indirect antiglobulin technique, and were generally unaffected by ficin pretreatment of test cells. The majority reacted poorly in EM-V LISS when 10 minute incubations were used. Cord red blood cells showed normal expression of the antigens. Serologic difficulties were due to relative antigen fragility in vitro of patients' samples, varying expression of antigen strength, relative low antibody avidity, and in 48% of the sera coexistence of additional unrelated alloantibodies. Antigen frequencies for Yka, Csa, McCa and Kna ranged between 90 and 99%, also displaying racial differences.