Acute and chronic tubulointerstitial diseases are the result of the interplay of renal cells and inflammatory cells and their products. Lethal or sublethal injury to renal cells leads to expression of new local antigens, inflammatory cell infiltration, and activation of proinflammatory and chemoattractant cytokines. These cytokines are produced by inflammatory cells (ie, macrophages, lymphocytes) and also by the renal cells (ie, proximal tubule, vascular endothelial cells, interstitial cells, fibroblasts). The outcome can be acute or chronic nephritis.