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

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: R1R1: 9,900-12,200; r'r': 8,200-9,700; ryr: 8,600; RNRN: 6,600; r'xr: 6,200; RB1r: 6,200; RZRZ: 5,400; Cdes: 4,800-5,100; R2R2: 3,600-5,800; RORO: 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.