Well, in a way we do know this. In Mollison's Blood Transfusion in Clinical Medicine (cited above), this time in Chapter 5, they talk about work showing how often giving D+ blood to a D- patient, just once, produces a response. They talk about 15% of the random population being "super responders" (my non-scientific phrase, not theirs!). In one study, <50% of D- volunteers produced a serologically detectable after 6 months after injection with 0.5 to 1mL of D+ red cells. BUT, this implies that some of them did, and it implies that it was more than, say, 1%. To my mind, this also debunks the practice of looking for an antibody response for 14 days, and if nothing is detectable, go ahead and give more of the same. I know that the D antigen is easily the most immunogenic of the common antigens, but K and c are not that far behind. In Mabel's case, therefore, where her blood supplier is miles from her hospitals, it would be best to regard all of her patients as potential "super responders", particularly as there is no way of telling in which category her patients will fall, prior to transfusion. :confused: