ROLE OF COMPLEMENT IN RENAL TUBULAR DAMAGE

Deposition of immunoglobulins, complement proteins Clq, C3c, C3d, C4, C5, C6, C7, C8, C9, and terminal complement complex neoantigens in the renal tubulointerstitium was studied in serial sections by immunofluo rescence microscopy. Renal tissue from 45 cases with various glomerula r diseases, including 8 controls, was studied, The patients were divid ed into groups; one with tubulointerstitial lesions (24 cases) and the other without (13 cases). The immunoproteins were deposited mainly in the tubular basement membrane and blood vessels. Compared with contro ls there was a significantly increased staining score for C5 to C9 in the tubular basement membrane in both disease groups. However, the inc rease in terminal complement complex neoantigens score was significant only in the disease group with tubulo interstitial lesions. The chang es in C3d score were not significant. Serial sections showed consisten t and heavy ribbon-like deposits of complement proteins C3d, C5 to C9, and terminal complement complex neoantigens in corresponding location s of the segments of tubular basement membrane, mainly in the disease group with tubulointerstitial lesions and especially in the damaged tu bules. These findings suggest that in situ activation of the complemen t cascade leads to the deposition of terminal complement complex neoan tigens. Complement activation in the basal area of the tubules may, th erefore, be an important pathogenetic mechanism in tubulointerstitial damage.