Observations of the Number of Available c, D, and E Antigen Sites on Red Cells

Abstract

Abstract. The number of available antigen sites within the Rh system were estimated using trace‐labelled antibodies. The results were as follows, given as the number of sites per red cell: c‐antigen: on cc cells, 70,000–85,000: on Cc, 37,000–53,000; D sites on cells of phenotype ‐D‐: 110,000–202,000; E‐antigen sites showed considerable heterogeneity depending on phenotype as well as source of anti‐E, and estimates varied between 450 and 25,600; e‐antigen: on eE cells, 13,400 and 14,500: on ee cells, 18,200 and 24,400. The average equilibrium constants of the antibodies were: anti‐E, 4 × 10 8 1/mol; anti‐e, 2.5 × 10 8 1/mol; anti‐c, 3.2 × 10 7 and 5.6 × 10 7 1/mol.