The Quantitation of D Antigenic Sites in Partial D and Weak D Variants by Flowcytometry

Aim  The aim of the study is to quantitate D antigenic sites on RBC in weak D and partial D variants in Indian population by flowcytometric method. Method  Dantigenic sites were estimated in 48 cases of partial D, eight cases of weak D (identified by serological methods) and normal Rh phenotypes subjects by flowcytometric technique. The indirect immunoflourescence method was employed using thirty epitope specific monoclonal anti-D as primary antibody. The D antigenic sites were calculated using standard RBC with known D antigenic sites. Result  The mean (±I S.D) D antigenic sites per RBC in weak D and partial D were 4503 ± 2067 and 6750 ± 3426 respectively. In R1R1 phenotype the range of D antigenic sites was 16500 ± 2500 and in R1r it was 10600 ± 2520. In four cases of weak D sites were in range of 1700 to 3500 and in other four it was 5000 to 7200 D sites/RBC. Among partial D variants DVI had minimum, and DVa had maximum number of D sites. Conclusion  Flowcytometry is a very good tool for demonstrating minor differences in D antigen sites in partial D and weak D when serological methods are not conclusive.