[1541] 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.

Predominant IgG subtype composition in glomerular and tubular basement membrane immune complex deposits in biopsies with proliferative lupus nephritis.

Case Number	Glomerular	TBM	Inflammation
1	1	3	absent
2	1,3	1	absent
3	1,2,3	2,3	absent
4	1,2,3	1	present
5	1,3	2,3	absent
6	1,2,3	3	present
7	1,2,3	1	present
8	1,3	1	absent
9	1,2,3,4	1,2	absent

TBM=tubular basement membrane

Therefore it appears that, in native kidney biopsies with lupus nephritis, the pattern of IgG subtype staining in tubulointerstitial deposits does not always correlate with that seen in glomerular deposits. Six of these biopsies showed no interstitial inflammation, three biopsies showed varying degrees of interstitial inflammation. The presence/ absence of interstitial inflammation did not appear to correlate with the IgG subtype composition of the TBM deposits. All of these nine biopsies with discrepant TBM IgG subtype composition were cases of proliferative lupus nephritis with or without membranous component. Cases of purely membranous lupus nephritis were not considered because overall they showed very little to none TBM staining.
Conclusions: Based on our data, it appears that the pathogenesis of TBM deposits is different than that of glomerular deposits.
Category: Kidney (does not include tumors)

Wednesday, March 24, 2010 1:00 PM

Poster Session VI # 239, Wednesday Afternoon