MHC CLASS-II, ANTIGEN PRESENTATION AND TUMOR NECROSIS FACTOR IN RENAL TUBULAR EPITHELIAL-CELLS

Proximal tubular (PT) epithelial cells express MHC class II (Ia) antigens in immunologically-mediated renal injury. To study the role of PT as accessory cells, we generated several murine PT-like epithelial cell lines by transformation with origin-defective SV40 DNA. These transformed cell lines display typical alkaline phosphatase and γ-glutamyl-transpeptidase enzyme activity, proliferation to epidermal growth factor (EOF) and sodium-dependent glucose uptake. Clonal lines of transformed tubular cells from both normal C3H/FeJ and autoimmune MRL-lpr mice do not constitutively express Ia antigens or mRNA for class II. However, stimulation with recombinant interferon-γ(rIFN-γ) induces Ia mRNA and surface product in the cell lines. These Ia-positive cells can process and present hen egg-white lysozyme (HEL) to antigen-specific Iak-restricted T cell hybrids. Unstimulated tubular cells do not express detectable IL-1α, IL-1β, TNF-α, or IL-6 mRNA. However, stimulation with IL-1α or LPS induces TNF-α transcripts. We conclude that these cell lines have characteristics most consistent with a proximal tubular origin. They also bear characteristics of accessory cells such as processing and presentation of antigen and TNF-α gene expression. We speculate that PT have the capacity to participate in the pathogenesis of immune renal injury.