Characteristics of a human liver allograft--derived T-cell line that exhibits suppressor activity

In an attempt to identify predominant cell populations that may mediate liver allograft dysfunction, the phenotypic and functional characteristics of lymphoid cells propagated from needle biopsy specimens of rejecting liver transplants were examined. In one case, a T-cell line of host phenotype propagated from a liver allograft biopsy demonstrated significant in vitro suppressor activity. This T-cell line (designated JB) was maintained for almost one year in culture with medium containing human recombinant interleukin 2 and with weekly stimulation by an Epstein-Barr virus-transformed B-cell line derived from the liver donor. Repeated analyses demonstrated that the JB line was phenotypically stable and predominantly CD3+ (86-93%), CD4+ (88-96%), DR+ (96%), Leu8-, CD45R-, CD16-, with a minor CD8+ cell population (less than 5%). The JB line demonstrated proliferative responsiveness upon coculture with cells expressing disparate donor HLA antigens but no in vitro cytotoxic activity. However, JB cells significantly (greater than 90%) suppressed mixed lymphocyte reaction or phytohemagglutinin stimulation of nonautologous peripheral blood lymphocytes. Supernatants of JB cells that had been cultured alone or with irradiated (6000 rads) Epstein-Barr virus-transformed donor B cells mimicked the suppressive activity of the JB cell line, either upon addition in vitro or by transient (4 hr) pretreatment of responder cells at 20 degrees C. JB cell supernatants were nontoxic and free of tumor necrosis factor activity, and their suppressive activity was dose-dependent, nondialyzable (greater than 100 kDa), not overcome by exogenous interleukin 1 or interleukin 2, and heat-resistant up to 56 degrees C. However, the suppressive activity of JB supernatants could be diminished or abrogated by treatment with high temperature (80-100 degrees C), reducing agents, trypsin, or absorption by peripheral blood lymphocytes at room temperature. The suppressive activity of JB cells and supernatants was not alloantigen-specific or major histocompatibility complex-restricted, did not shift mixed lymphocyte reaction kinetics, and was capable of inhibiting in vitro stimulation of peripheral blood lymphocytes in mixed lymphocyte reaction only when presented early in the culture. These findings provide the first evidence for a primary human allograft-derived T-cell line with suppressor-effective function.