Catherine M. Meyers

Regulation of Inducible Class II MHC, Costimulatory Molecules, and Cytokine Expression in TGF-β1 Knockout Renal Epithelial Cells: Effect of Exogenous TGF-β1

As reports of mice genetically deficient for TGF-β1 demonstrated aberrant renal class II MHC expression, we investigated inducible class II MHC expression on renal tubular epithelial cells derived from TGF-β1 knockout (–/–) and wild-type (+/+) mice. IFN-γ markedly upregulated class II MHC (I-Ab) expression in both (–/–) and (+/+) tubular epithelial cells. Coincubation studies of (+/+) and (–/–) tubular epithelial cells with IFN-γ+LPS, or pretreatment of these cells with TGF-β1, revealed inhibition of IFN-γ-induced I-Ab mRNA and cell surface expression that occurred via a decrease in class II transactivator gene expression in both (+/+) and (–/–) tubular epithelial cells. In addition, ICAM-1 was constitutively expressed on both (+/+) and (–/–) tubular epithelial cells and was upregulated by IFN-γ or IFN-γ+LPS. ICAM-1 expression in (+/+) and (–/–) tubular epithelial cells, however, was decreased by TGF-β1. Parallel analysis evaluating B7-1 expression detected low levels of B7-1 in unstimulated (+/+) and (–/–) tubular epithelial cells that were increased by IFN-γ, LPS, and IFN-γ+LPS. IFN-γ+LPS-mediated upregulation of B7-1 was also blocked by pretreatment with TGF-β1. Cytokine analysis detected significantly higher levels of TNF-α and MIP-1α mRNA in all treated (–/–) preparations than in (+/+) tubular epithelial cell controls. These studies demonstrate normal patterns of class II MHC, ICAM-1, and B7 expression in TGF-β1 (–/–) tubular epithelial cells in response to IFN-γ, LPS, and TGF-β1. Upregulated cytokine expression at baseline and in response to proinflammatory mediators is apparent in (–/–) tubular epithelial cells, however, and suggests that dysregulation of cytokine expression in inflammatory responses may be a primary event in multifocal inflammation observed in TGF-β1-deficient animals.

Immune Reactivity Following CD40L Blockade: Role in Autoimmune Glomerulonephritis in Susceptible Recipients

To investigate the role of costimulation in autoimmune glomerulonephritis that develops in the setting of murine chronic graft-vs-host disease (cGVHD), we examined the effects of blocking CD40L, a costimulatory marker expressed on activated CD4+ T cells, in recipient mice. These studies addressed the potential role of CD40L blockade in preventing disease and in downregulating its expression in animals with evidence of autoreactivity. Animals treated acutely with anti-CD40L antibody at disease induction do not develop circulating anti-DNA antibodies, proteinuria, or histologic evidence of renal disease. If treatment is delayed for two weeks, after circulating anti-DNA antibodies are apparent, all animals develop massive proteinuria by 14 weeks after disease induction. Renal histology of kidneys from the delayed treatment and control groups reveal similar glomerular immune deposits, and intense staining for CD4, ICAM-1, and I-A(b) in areas of mononuclear cell infiltration. Long-term treatment studies begun two weeks after disease induction is not disease-protective, as all animals develop massive proteinuria and renal disease by 14 weeks. These studies suggest that early CD40L signaling events are critical to induction of allogeneic interactions and autoreactivity in cGVHD, but that short-term or chronic CD40L blockade, once autoreactivity is evident, does not abrogate systemic autoreactivity and renal involvement.