Serum C3d levels in tropical pulmonary eosinophilia.

BACKGROUND & OBJECTIVES Results of earlier studies to evaluate the possible role of complement system in tropical pulmonary eosinophilia (TPE) using classical methods like serum haemolyte component CH50, C3 and C4 levels were inconclusive. In this study we determined levels of serum C3d which is a catabolic fragment of C3, to find out any direct evidence of activation of the complement system in TPE. METHODS The study population consisted of 3 groups. Group A consisted of 37 patients with well characterized TPE. In group B, 26 patients with pulmonary eosinophilia had similar respiratory and haemotological features as in Group A but had associated worm infestation in stool. The control group consisted of 39 healthy volunteers. Serum C3d levels were determined by sandwich ELISA technique. RESULTS The serum C3d levels in TPE patients were not significantly different from those of the patients of group B or the normal controls. INTERPRETATION & CONCLUSIONS Absence of significant change in serum C3d goes against the possibility of complement activation in TPE. Results of our study suggest that complement system is unlikely to play a pivotal role in pathogenesis of TPE.