Blood group A expression on platelet GPs and GSLs is dictated by A₁ subtype and is independent of Lewis phenotype. (A) Western blot results for 25 apheresis platelet donors, stained with anti-A (MoAb Birma1). Positive staining was observed in A₁ but not A₂ individuals. Strong staining was observed in 2 ABH-HPX donors (lanes 21 and 25). (B) The intensity of HPA staining on platelet membranes (% HPA⁺ platelets) is related to the intensity of GP-A staining by Western blot, as determined by scanning densitometry (area), where y = 46.5 + 6.43x, R = 0.91. (C) Platelet GPs separated by SDS-PAGE and stained with Coomassie Brilliant Blue. Lane numbers refer to the same donor samples shown in panel A. Lane S, molecular weight standards. (D-F) Isolated neutral GSLs from the same donors in panel A, immunostained with anti-A (D), anti-Le^b (E), and anti-Le^a (F). Solvent C-M-W 65:25:4 (vol/vol). R_f indicates relative mobility.