Discrepancies in IgG Subtype Composition between Glomerular and Tubulointerstitial Immune Complex Deposits in Proliferative Lupus Nephritis
A Satoskar, S Brodsky, A Albarwadi, GM Nadasdy, T Nadasdy. Ohio State University, Columbus, OH
Background: Tubulointerstitial immune complex deposition is a histologic characteristic of lupus nephritis. However, the degree of tubular basement membrane (TBM) immune complex deposition does not seem to correlate well with glomerular immune complex deposition. We suspect that TBM immune complex deposits differ from glomerular deposits. We studied if there is any correlation in the IgG subtype staining between glomerular and TBM immune complex deposits and also if presence/absence of interstitial inflammation correlated with any IgG subtype predominance in the TBM deposits.
Design: Native renal biopsies with lupus nephritis from 60 patients were stained with antibodies to the IgG subtypes by direct immunofluorescence (IF). TBM deposits were present in 39 of the biopsies. Staining was semiquantitatively scored as 0, trace, 1+ (mild), 2+ (moderate) and 3+ (prominent).
Results: IgG1, IgG2 and IgG3 were the predominant subtypes in the glomerular immune complex deposits. The tubulointerstitial deposits followed this pattern but with a milder intensity. However, in nine biopsies, the predominant IgG subtype composition in the TBM deposits differed from that in the glomerular deposits.