What is Red Blood Cell Alloantibodies?
Red blood cell alloantibodies are immunoglobulins — predominantly IgG, though IgM antibodies also occur — formed when the immune system encounters foreign red cell antigens through transfusion, pregnancy, or rarely transplantation. The initial antibody screen uses the indirect antiglobulin test: patient serum is incubated with reagent red cells of known antigen phenotype, and after washing, anti-human-globulin reagent detects bound IgG or complement. A positive screen triggers antibody identification panels to determine specificity. Clinically significant antibodies are those capable of shortening red cell survival in vivo — Rh (D, C, E, c, e), Kell, Duffy, Kidd, and S/s being the most frequent — while others such as Lewis or P₁ rarely cause haemolysis.