We here describe the isolation, characterization, profile of lymphokine expression and T-cell-receptor gene rearrangement pattern of 444P.3, a CD3+ CD4+ CD8- 4B4+ interleukin-2 (IL-2)-dependent clone derived from the malignant ascites of a patient with renal cell cancer. The 444P.3 clone exhibited unique antitumor specificity between days 45 and 84 in culture and then lost its lytic, but not its proliferative, capacity. To our knowledge this is the first description of a specific antitumor reaction in a patient with renal cell cancer against autologous tumor. IL-2-expanded 444P.3 cells, tested on day 104 in culture, expressed mRNA for tumor necrosis factor (TNF), IL-2 and tumor growth factor beta (TGF-beta) but not for IL-1, lymphotoxin or granulocyte/macrophage-colony stimulating factor (GM-CSF). The parental noncloned population expressed mRNA for TNF, lymphotoxin, GM-CSF and TGF-beta but not for IL-1 beta or IL-2. Analysis of established human T cell clones should include profiles of lymphokine secretion in addition to growth and proliferation patterns, antitumor activity and surface phenotype. Such characterization of clones may provide a better understanding of the immunoregulatory role and functional potential of various T cell subsets involved in human antitumor reactivity.