TSLPtg and TSLPtg/FcR?/? mice show markedly increased monocyte/macrophage infiltration in glomeruli and they have increased T cell infiltration in interstitium

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TSLPtg and TSLPtg/FcR?/? mice show markedly increased monocyte/macrophage infiltration in glomeruli and they have increased T cell infiltration in interstitium. immune deposits, mesangial cell proliferation, considerable mesangial matrix accumulation, and macrophage influx. TSLPtg/FcR?/? mice experienced more glomerular immune complex deposits and higher levels of circulating cryoglobulins, IgG2a, IgG2b, and IgM, compared with TSLPtg mice. TSLPtg and TSLPtg/FcR?/? mice developed similar levels of proteinuria. These results exhibited that deletion of activating FcRs does not confer protection in this model of immune complex-mediated MPGN. The findings contradict accepted paradigms around the role of activating FcRs in promoting features of glomerulonephritis as seen in other model systems. We speculate engagement of FcRs on cells such as monocytes/macrophages may be important for the clearance of deposited immune complexes and extracellular matrix proteins. Deposition of immune complexes (ICs) is usually a major initiation step for many types of glomerulonephritis. After deposition in tissues, the Fc portion of immunoglobulins (Ig) in ICs binds to Fc receptors (FcRs) on effector cells. In the mouse, four FcRs for IgG have been recognized.1,2 Among them, FcRI, III, and IV are polymeric receptors with a common adaptor chain (FcR) bearing the immunoreceptor tyrosine-based activation motif. The FcR chain is necessary for cell surface expression and transmission transduction of FcRI, III, and IV. The FcR chain is also a subunit of FcRI and FcRI.3,4 Binding of FcRI, III, and IV by IgG transduces activating signals via phosphorylation of the FcR immunoreceptor tyrosine-based activation motif leading to activation of syk tyrosine kinase and downstream signaling pathways such as phospholipase C- and phosphatidylinositol-3 kinase. Deletion of the FcR subunit prospects to functional loss of FcRI, III, and IV.5 In contrast, the monomeric FcRIIb has an immunoreceptor tyrosine-based inhibitory motif in its cytoplasmic tail. Ligand binding to FcRIIb prospects to recruitment of inhibitory phosphatases such as src homology domain name type-2-made up of tyrosine phosphatase 1 and SH2-made up of inositol polyphosphate phosphatase that dampen immunoreceptor tyrosine-based activation motif-initiated activation.1,6 An emerging paradigm for the mediation of inflammation is that a balancing of engagement of co-existing activating and inhibitory FcRs on the surface of effector cells determines the severity of inflammatory response to injury.4,7 Membranoproliferative glomerulonephritis (MPGN) in humans is typically initiated by deposition of immune complexes. The mechanism by which MPGN develops subsequent to immune complex deposition is still not well comprehended. We have characterized a mouse model of MPGN resulting from deposition of cryoglobulin made up of Shikonin ICs, which result from overexpression of thymic stromal lymphopoietin (TSLP), a cytokine that causes abnormalities in B cell development.8,9 TSLP transgenic (TSLPtg) mice develop mixed cryoglobulinemia and a systemic inflammatory disease that involves the kidney, lung, spleen, liver, and skin. These mice develop renal disease that closely resembles human cryoglobulinemia-associated MPGN. 8 The glomerular injury in these mice is usually characterized by considerable subendothelial and mesangial immune deposits, marked macrophage influx, and mesangial cell proliferation and matrix growth. Immunofluorescence microscopy shows massive glomerular deposition of immunoglobulins and match. We have analyzed the effect of the inhibitory FcRIIb on this MPGN model previously and showed that FcRIIb deficiency in TSLPtg mice resulted in more severe kidney disease with more infiltrating macrophages and increased cell proliferation in glomeruli.10 Here we present complementary studies in which the effect of deletion of the activating FcRs on the disease in this model was tested, and present the amazing result that this intervention produced no improvement in renal and systemic disease in TSLPtg mice and indeed lead to higher concentration of circulating cryoglobulins and more deposition of ICs in the kidney in these mice. Materials and Methods Animals The experimental protocol of this study was examined and approved by the Animal Care Committee of the University or college of Washington. Mice were housed under standard conditions and received normal chow and water in a specific pathogen free facility. TSLPtg mice on C57BL/6 background have been reported previously.8 FcR chain knockout (FcR?/?) mice on C57BL/6 background were provided by J. V. Ravetch Shikonin (Rockefeller University or college, New York, NY) and have been explained previously.11 TSLPtg mice were crossed to FcR?/? mice. Cohorts of FcR+/+ (wild-type), FcR?/?, TSLPtg, and TSLPtg/FcR?/? mice (= Rabbit Polyclonal to TCEAL4 6 in each group), all females, were sacrificed and analyzed at age 30 days and 50 days when kidney disease is usually early in its development (30 days) and when it is fully developed (50 days) in female TSLPtg mice, as previously documented.8,10 Immune Thrombocytopenia Induced by 6A6 Antibody To establish the intact function of activating FcRs in TSLPtg mice, and its absence in TSLPtg/FcR?/? mice, a platelet depletion Shikonin assay that requires the presence of intact FcRs was used, as previously described.12,13 Blood samples were collected from TSLPtg and TSLPtg/FcR?/? mice and placed into EDTA tubes to prevent clotting. The assay utilizes the monoclonal.