Doses of as little as 50 micrograms of a soluble chaotropic extract of bovine tubular basement membrane (Bov-KBr-TBM) with adjuvants induced anti-TBM antibodies and tubulointerstitial nephritis (TIN) in Brown Norway (BN) rats. The lesion was shown by renal histology, by deposition of IgG and C3 along TBM, and in terms of the humoral and cellular immune responses to compare to that produced by the standard immunization (particulate bovine TBM) for this model of TIN in BN rats. More than half of the mononuclear cells in kidneys of BN rats with TIN bore various T-cell antigens (monoclonal antibodies W3-13, W3-25, and OX-8), and most of the infiltrating cells were positive for Ia (monoclonal antibody OX-6) by indirect immunofluorescence. Purified suspensions of these mononuclear infiltrates were prepared by using Ficoll-Hypaque gradients and the fluorescence-activated cell sorter (FACS) to eliminate renal tubular epithelial cells. The purified mononuclear cells, cultured for 5 days, incorporated thymidine in response to concanavalin A (Con A), Mycobacterium tuberculosis purified protein derivative, and Bov-KBr-TBM but not in response to a variety of autologous renal antigens. After culture for 5 days in Bov-KBr-TBM and Con A supernatant, lymph node cells (LNC) from Bov-KBr-TBM-immunized BN rats passively transferred TIN to naive BN rats. Although no cells reactive with autologous renal antigens were detected in the renal infiltrates, the transfer of disease with propagated LNC suggests that elements of the cellular immune system, in addition to anti-TBM antibody, contribute to the generation of this BN-TIN.