Observations of the Number of Available G (rhG,Rh 12) Antigen Sites on Red Cells1

Abstract. The number of available G antigen sites within the rhesus system were estimated using trace-labelled antibody. The results given as available antigen sites_ per cell were as follows: R₁R ₁ : 9,900-12,200; r'r': 8,200-9,700; ryr: 8,600; RNaN: 6,600; r‘^xr: 6,200; RB₁r: 6,200; R_ZR_Z: 5,400; Cdes: 4,800-5,100; R₂R ₂ : 3,600-5,800; R₀R ₀ : 4,500-5,300; R₂r 4,200; r“Gr: 1,700-3,600; RB₂r: 1,400-1,900. The G antigen is detected in optimal amount on C-positive samples. When D is present without C, the number of G sites is apparently dependent on the expression of all the D antigens within the recognized six categories of D antigens.