Oka: an erythrocytic antigen of high frequency.

Clinically significant antibodies to a 'new' high-frequency antigen on red blood cells have been detected in the serum of a Japanese woman. The notation Oka has been given to this antibody and its corresponding antigen. Two of the patient's siblings are Ok (a--) but a large number of red cell samples lacking common antigens were tested and found to be Ok (a+). The antibody reacted by the antiglobulin test with blood samples from random blood donors and with more than 4,000 red cell samples from Oriental blood donors and patients.