Anti-Kp^a and Anti-Kp^b are antibodies directed to antigens in the Kell blood group system. The Kp^a and Kp^b antigens were reported in 1957 and 1958 respectively and have been implemented in immediate and delayed Haemolytic Transfusion reactions and Haemolytic Disease in the new born. Indirect agglutination of red cells that carry these antigens occur in the antiglobulin phase.  In the absence of these antigens, no indirect agglutination is generally observed.

The Biorex Diagnostics Anti-Kp^a and Anti-Kp^b reagent consists of human serum diluted in sodium chloride solution containing macromolecular potentiators and bovine albumin. The reagent requires no further dilution or addition for recommended techniques.