Role of complement in tubulointerstitial injury from proteinuria

The complement system is being increasingly implicated in the pathogenesis of progressive renal disease resulting from persistent proteinuria. It has recently been established that renal tubular cells can produce complement, activate complement, and respond to complement activation. Complement proteins that pass through the glomerular barrier along with other serum proteins in the proteinuric state may become activated at the tubular epithelial brush border, and lead to a cascade of events culminating in cell injury. Furthermore, nephrotic components in the urinary space may cause direct activation of the tubular cells to overexpress complement and contribute to local tissue injury. In this review, we will discuss the current evidence supporting a role for complement in the pathogenesis of progressive tubulointerstitial damage in the proteinuric state. The possibility of complement inhibition intervening in progressive tubulointerstitial injury due to proteinuric glomerular disease will also be considered.