ROLE OF T-CELLS IN THE MEDIATION OF HEYMANN NEPHRITIS .2. IDENTIFICATION OF TH1 AND CYTOTOXIC-CELLS IN GLOMERULI

The role of immunoglobulin (Ig) and complement as mediators of Heymann nephritis (HN) has been questioned by recent studies showing that HN can be induced in a C6-deficient rat that cannot assemble the membrane attack complex of complement. Also, the severity of HN can be reduced by therapy directed at CD8(+) T cells, which has no effect on antibod y (Ab) production or immune deposits. To identify whether T cells may contribute to the glomerular injury of active HN in Lewis rats, the mo nonuclear infiltrate and cytokine mRNA in glomeruli and kidney interst itium were examined. Groups of Lewis rats immunized with Fx1A in CFA d eveloped HN, and were compared to controls that received CFA only. Pro teinuria, the marker of glomerular filtration barrier dysfunction, was absent at four weeks but present at eight weeks in HN. Serum anti-Fx1 A Ab and glomerular Ig were present in HN at both time points. Immunop eroxidase staining with monoclonal Abs identified, at eight weeks, a g lomerular infiltrate of CD4(+) and CD8(+) T cells, and macrophages, bu t not NK cells. Semiquantitative RT-PCR of isolated glomeruli at eight weeks demonstrated expression of cytokine mRNA for Th1 CD4(+) cells ( IFN-gamma and TNF-beta/LT, but not IL-2), cytotoxic CD8(+) T cells (gr anzyme A and perforin), and macrophages (TNF-alpha and IL-10), but not Th2 CD4(+) cells (no increase in IL-4, IL-5 and IL-6). At eight weeks , the cellular infiltrate and pattern of cellular activation in glomer uli was different to that in renal cortex. In the cortical infiltrate CD8(+) cells were a lesser component, and NK cells were increased, as were CD4(+) cells and macrophages. RT-PCR identified increased cytokin e mRNA for macrophages, Th1 and Th2 cells, but not cytotoxic effector T cells. At four weeks, T cells including CD4(+) and CD8(+) cells were identified in the isolated glomeruli of rats with HN, but there was n o increase in cytokine mRNA expression. There was no infiltrate or inc rease in cytokine mRNA detected in renal cortex at four weeks. Anti-Fx 1A Ab's and glomerular deposition of Ig develop many weeks before the onset of proteinuria, when there is only a small cellular infiltrate p resent. The progressive development of infiltrates of activated T cell s, principally Th1 and cytotoxic effector cells, and macrophages, with in glomeruli is coincident with the development of proteinuria. These findings raise the possibility that these cells contribute to the medi ation of the glomerular injury and proteinuria of HN.