Expression of complement regulatory proteins in the developing human kidney

Complement homologous restriction factor CD59 and complement receptor CD35 are typically involved in the regulation of the host defense system. Recent observations in the human fetal kidney suggest a further role for compleme nt cell surface regulators CD35 and CD59 in kidney development and maturati on. We investigated this possible role by localizing CD35 and CD59 protein and mRNA in the developing and adult kidney. Adult tissue and fetal tissue ontogeny were analyzed using immunohistochemistry and in situ hybridization . CD35 protein and mRNA were localized to the podocyte of the glomerulus in the human fetal and adult kidney. Expression was initiated after vasculari zation of the early developing glomerulus. CD59 protein and mRNA were obser ved as early as 8 weeks' gestation and were localized primarily to the uret eric duct epithelium in the fetal kidney and predominantly to the collectin g duct in the adult. Interestingly, CD59 expression was translocated from t he basolateral surface in the fetal kidney to the apical surface in the adu lt kidney. The specific spatial and temporal expression of CD35 and CD59 su ggests a possible role for these complement regulatory proteins in renal ce ll differentiation.