[Significance of human Tr cell in gastric cancer --with special reference to suppressor cell activity]

Peripheral blood lymphocytes from gastric cancer patients and normal donors were divided into T, non T, Tr, and T non-r cell fractions. Suppressor cell activity of each fraction and surface antigen of T cell subsets were investigated. T and Tr cell fractions activated by concanavalin A (Con A) significantly depressed the lymphocyte proliferative responsiveness (LP) to phytohemagglutinin (PHA) of responder autologous lymphocytes, but non T and T non-r cell fractions didn't. LP response to PHA of responder autologous cells were depressed by Tr cell fraction from gastric cancer patients without Con A activation, but not from normal donors. The percentage of Tr cells in T cells increased from 8.9% to 18.2% in gastric cancer patients, and from 4.7% to 9.5% in normal donors when lymphocytes were activated by Con A for 24 hours. The percentages of Tr cells reacting with OKT3, 4, and 8 monoclonal antibodies were 72.5%, 29.0% and 43.4%, respectively. Therefore, Tr cell was relatively enriched by OKT8 cell. The percentage of Tr cells and suppressor cell activity increased when normal lymphocytes were incubated with sera from gastric cancer patients for 24 hours and suppression by T, Tr and T non-r cell fractions 23%, 8% and 5%, respectively. From these results it is suggested that Tr cells contain suppressor precursors which can be activated by Con A in vitro and matured suppressor cells which have been already activated in vivo, and that higher proportion of suppressor precursors is found in gastric cancer patients as compared with normal donors. Furthermore, it is indicated that cancer sera may contain factors which induce suppressor cell and induction of suppressor cell activity requires the interaction between Tr cell and T non-r cell.