What is the cause of anti-K antibodies in blood?
Q: I have O RhD positive blood group with anti-K antibodies. I have been diagnosed with autoimmune haemolytic anaemia. I have never had a blood transfusion. What could be the cause of this and how long will it take to get cured? I am currently taking prednisolone daily.
A:The Kell blood group system is one of the major antigenic systems in human red blood cells and is clinically important because Kell antigens are important in transfusion medicine, autoimmune haemolytic anaemia, and haemolytic disease of the newborn. Individuals who lack a specific Kell antigen may develop antibodies against Kell antigens when exposed to red blood cells containing that antigen (called alloimmunisation). There is production of antibodies (IgG) when the immune system is exposed to a ‘foreign’ antigen not present on one’s own red blood cells. These can attack one’s own red blood cells destroying them (autoimmune haemolytic anaemia, AIHA) or, in a pregnant woman, cross the placenta and affect the baby (haemolytic disease of the newborn, HDN). The most common routes by which a woman gets sensitised are via blood transfusion or feto-maternal (passage of blood from the baby to the mother) which is associated with delivery, trauma, spontaneous or induced abortion, ectopic pregnancy, or invasive obstetric procedures. Both AIHA and HDN may be severe when caused by anti-Kell antibodies. The Kell blood group\system consists of over 20 different antigens (KEL1 to KEL24) with over 90% of the population being Kell negative. The k antigen (Cellano or K2) is far more common than K antigen (Kell or K1). The K (K1) antigen is very immunogenic and causes strong reactions in case of mismatched blood transfusion and severe fetal anaemia in sensitised mothers. It is produced only after exposure to the antigen as a result of pregnancy (most likely in your case) or repeated blood transfusions and thus the anti-K antibody is seen frequently in individuals. The k antigen (K2) too is immunogenic but as it is present in most individuals, the anti-k antibody is much less common.