Weak D antigen - Revisited.

ABSTRACT

D antigen is the most immunogenic antigen in the complex Rh blood group system discovered in the year 1939. There is a lot of polymorphism in its phenotype due to genetic heterogeneity. Certain mutations and /or deletions lead to a weak phenotype defined by decreased density of antigen sites which require the use of anti human globulin for detection. The need for detection of the weak D antigen was to prevent alloimmunization by this blood if transfused to a D negative patient especially to women in child bearing age group. This contention is however, controversial and not proven beyond doubt. Moreover, the use of potent monoclonal D typing antisera detects low density of weak D antigens thus obviating the use of anti human globulin. We have assessed the incidence of Rh negative and weak D blood groups in the Garhwal region of Uttarakhand and reviewed the literature regarding the controversies in the clinical significance of weak D antigen.