Rh18 and hrS blood groups and antibodies.

Anti-hrS, also known as the Shabalala antibody, is unlikely to be found in unabsorbed human serum. The term 'anti-hrS, was devised by Shapiro in 1960 to describe the antibodies remaining in the absorbed serum after anti-Rh18 had been absorbed with R2R2 red cells. R2R2-absorbed anti-Rh18 (anti-hrS), although an interesting research tool, is therefore clinically irrelevant. Unabsorbed anti-Rh18, on the other hand, is a clinically significant antibody. It is compatible not only with Rh-'deleted' and Rhnull red cells, as described by Shapiro, but is also compatible with the red cells of numbers of Southern African Blacks and Coloureds (mixed race) who have Ro, Rou or R2r phenotypes. Anti-Rh18 causes haemolytic disease of the newborn and, when uncontaminated with other antibodies, is a further reagent for resolving Rh grouping problems.