Role of C1q in Rhesus haemolytic disease of the newborn.

ABSTRACT

Present study attempts to find out if maternal anti-D can bind the first complement component C1q and its impact on phagocytosis and severity of Rh haemolytic disease of the newborn (HDN). One hundred Rh immunised women were enrolled, however six having Rh(D) negative infants were excluded. Immunometric assay revealed that of 94 sera, 18 (19.1%) were able to bind C1q but failed to bind C3. Six mothers had anti-C (two bound C1q) and one had anti-E (C1q nonbinding) in addition to anti-D. Various characteristics of anti-D like titre, concentration, IgG subtypes and phagocytic activity showed comparable results (P > 0.3) in C1q binding and nonbinding groups. No significant difference in the severity of Rhesus haemolytic disease of the newborn (Rh HDN), judged by the outcome of pregnancy, cord blood haemoglobin, peak and pre exchange transfusion (ET), indirect serum bilirubin and requirement of ET, was observed in these two groups. Hence this study suggests that though some anti-D sera can bind C1q, there is no further activation of complement pathway and the severity of Rh HDN is not influenced by this phenomenon.