Quantitation of Ina blood group antigens

Using indirect immunoradiometric assay the mean (+/- SD) number of Ina antigenic sites per erythrocyte was estimated to be 73857 +/- 18285 in normal adults and 20142 +/- 8571 in newborn infants. Pregnant women showed temporary reduction in Ina antigens (28144 +/- 13857), which returned to normal levels, 3-6 months after delivery. Ina antigens were shown to be denatured by papain treatment of red cells, proving it to be of glycoprotein nature.