Antigen processing and presentation by glomerular visceral epithelium in vitro. Although macrophages are considered the prototype of antigen presenting cells (APC), recent studies have emphasized the potential role of several parenchymal and mesenchymal cells in this process. We have studied the capacity of cultured glomerular visceral epithelial cells (GEC) to act as effective APC and compared this capacity with that demonstrated by peritoneal macrophages Affinity-purified and in vitro propagated rat GEC were exposed to hen egg lysozyme, keyhole limpet hemocyanin, and cationic ferritin. As effector cells, we used antigen-specific T cell hybridomas; the level of antigen presentation was assessed by determining the level of interleukin 2 (IL-2) present in tissue culture supernatants Cytokine-treated GEC were capable of processing and presenting all antigens in a dose-dependent manner. Crucial for antigen presentation were intracellular processing of antigen and the presence of la on the cell surface. Our findings indicate that GEC can act as effective APC, and further suggest that this capacity may be relevant to cell-mediated immune injury at the level of the glomerular capillaries in vivo.