What is my wife's blood group?
Q: My wife is 28 years old and expecting our first baby next month. Her blood group was tested several times and the reports showed it to be B positive, but sometimes as B negative. We have got it checked in a good laboratory in Delhi. The report says B negative, but in the comments they have written Du positive. What does this mean? I am really worried. If there is an emergency, which blood group should be given to my wife?
A:Our red blood cells (and some tissues) have got chemical substances called antigens on their surface and the ability to form these antigens is governed by genes inherited from parents. The environment cannot influence our blood group, i.e. the blood group of an individual cannot change. The presence of these antigens (and their antibodies) has given rise to blood group systems and they play a role in blood transfusion and tissue typing. Many different (about 30) blood group systems are known in humans, but the ones of clinical significance are the ABO system, Rh system, Kell, MNS, Lewis, etc. The importance of blood group systems lies in transfusion and transplant medicine as we can receive blood (or organ) from only an individual whose blood group matches ours. In case of mismatch, the body's immune system recognises the foreign antigen and fights it leading to disease states. Thus, blood group matching is done so that compatible blood (or tissue) is selected. The Rh system is the second most important blood group system after the ABO blood group system and the Rh antigens are highly immunogenic (i.e. induce antibody production). In routine blood testing, the Rh blood group type is divided into Rh(D+) called Rh-positive and Rh(D-) called Rh-negative on the basis of the apparent presence or absence of Rh(D) antigen on the red cells. This is detected by adding a reagent to the red cells and noting if clumping of cells occurs or not. There is, however, a small group of individuals with apparently Rh(D-) red cells on routine testing, but that do react when the D-typing test is performed using selected anti-R (D) reagents by the indirect antiglobulin test. Such cells are designated Du. The frequency of the Du phenotype is about 0.2% overall and about 1.5% of all Rh(D-) women. Thus, Du variant is an Rh positive antigen which is weakly expressed on the red cells and such individuals are labelled Rh-positive. Nowadays, every apparently Rh-negative woman is further tested for the Du variant. So, your wife's blood group is B-positive.