Tubulo-interstitial disease in lupus nephritis. A morphometric study.

To test the hypothesis that immune complex deposition can mediate tubulo-interstitial damage in lupus nephritis, a correlative immunofluorescent (IF) and morphometric study of 43 renal biopsies from 39 patients with diffuse proliferative lupus glomerulonephritis was done. The point-counting method was used to determine the percentage of the cortical tubulo-interstitial system occupied by the mononuclear cell infiltrates (infiltrate index) and by the interstititum (interstitial index). The estimated amount of deposits containing immunoglobulin along tubular basement membranes and within the interstitium was expressed as a percentage of tubulo-interstitial volume. Interstitial cell infiltrates were present in 40 of the 43 biopsies and tubulo-interstitial immune deposits were noted in 29 biopsies. Linear regression analysis showed a statistically significant correlation between interstitial and infiltrate indices (r = 0.553, P less than 0.001). Correlations between (a) the extent of immune deposits and interstitial index (r = 0.239) and (b) immune deposits and infiltrate index (r = 0.280) were not significant. The results do not support the hypothesis that immune deposits mediate tubulo-interstitial injury and suggest that the damage is effected by the inflammatory cell infiltrates.