A protocol was successfully developed for reproducibly transferring experimental autoimmune orchitis (EAO) to naive recipient mice with sperm-specific T lymphoblasts. Cell donors were Balb/c mice immunized about 12 days earlier with homologous epididymal sperm capacitated in vitro with complete Freund's adjuvant. Draining lymph node cells were collected and subjected to a second challenge with the same sperm antigen in vitro. Sperm-specific T lymphoblasts were isolated on Percoll density gradients and propagated in the presence of interleukin-2 for 3 days and then were transferred intraperitoneally to naive recipients. As few as 3 x 10(6) sperm-specific T lymphoblasts were able to transfer EAO, which began on day 7 as infiltration of lymphocytes and macrophages and on days 14 to 21 developed to degenerative changes of spermatids and exfoliation of germinal epithelium. These pathologic alterations resemble a delayed type of hypersensitivity. The results show that sensitized T lymphoblasts can mediate an antigen-specific, mononuclear cell-invasive lesion in autoimmune orchitis.