Q: I have just found out that my blood group is O RH D positive; plasma contains Kpa - Red Cell Components. I am 21 weeks into my second pregnancy. What will this mean to my unborn baby & me? I would appreciate any information that you can give me on this subject.

A:The red blood cells have proteins on them called antigens, which play a role in blood transfusion and tissue typing. Each group of antigens (and their antibodies) comprises a blood group system and about 20 Blood group systems and seven antigen collections are known till date. The most important are the ABO and Rh systems, the mismatch of which can lead to major transfusion reactions, while several high-prevalence or public antigens and low-prevalence or private antigens that are not associated with known systems or collections are also defined (called minor blood groups). The ABO system classifies human blood into blood group A (presence of A antigen on red cells), blood group B (presence of B antigen), blood group AB (presence of both A & B antigens) and blood group O (absence of both A & B antigens). Persons with A blood group have anti-B antibodies, blood group B have anti-A antibodies, blood group AB lack any antibody while group O individuals have both anti-A and anti-B antibodies in their plasma (liquid part of blood). Blood transfusion requires matching of blood groups otherwise antibodies will attack and break down the red cells of the other blood group i.e. donor red cells may be destroyed by an antibody in the recipients plasma. In the Rh system either we have the Rh antigen (Rh positive) or lack it (Rh negative). There are no naturally occurring Rh antibodies in our blood and an Rh negative individual forms them if exposed to Rh positive red cells. The Kell System (named after the family of the antibody producer Mrs. Kellacher) is a minor blood group system in which there are four antigens: K (Kell) and k (cellano), and Kpa and Kpb. The Kp(a+)phenotype and the Kp(a-b-) phenotype are both rare. Blood can also be typed by several other minor antigens, such as Kell, Duffy, and Lewis. These minor antigens can become important when a patient has received many transfusions. These patients tend to build up an immune response to the minor blood groups that do not match their own. Upon receiving a transfusion with a mismatched minor blood group, they may have an adverse reaction. Hemolytic transfusion reaction due to interdonor Kell incompatibility are rare and need not worry you.