STUDIES ON THERMOPHILE PRODUCTS .10. FURTHER BIOLOGICAL PROPERTIES OFISOFATTY ACID-CONTAINING PHOSPHATIDYLGLYCEROL THAT ENHANCES THE INDUCTION OF SUPPRESSOR T-CELLS

Isofatty acid-containing phosphatidylglycerol (Fr. 7-C), isolated from Bacillus stearothermophilus UBT8038, enhances the induction of concan avalin A (Con A)-activated suppressor T (Ts) cells in a dose dependent manner (0.01-1 mu g/ml). Its further biological properties on mouse m ixed lymphocyte reaction (MLR) has been demonstrated. Fr. 7-C (0.01-1 mu g/ml) suppressed the MLR at 4 d in a dose-dependent manner when add ed at the start of splenocyte cultivation. Moreover, Fr. 7-C was effec tive in preventing the generation of cytotoxic T lymphocytes after the MLR. On the other hand, this fraction significantly enhanced the indu ction of Ts cells in the MLR carried out in any of the antigen-specifi c, antigen-nonspecific and major histocompatibility complex antigen-no nrestricted fashions. Fr. 7-C increased prostaglandin E(2), (PGE(2)) r elease approximately 2-fold in the culture supernatant of Con A-activa ted splenocytes, and PGE, release decreased dose-dependently when cult ured with indomethacin. The inhibitory effect by Fr. 7-C on the MLR wa s abrogated by the addition of indomethacin. The enhancement by Fr. 7- C on Ts cell induction was blocked by indomethacin in a dose dependent manner. These results strongly suggest that Fr. 7-C suppresses the ML R via the enhancement of antigen-nonspecific Ts cell induction mediate d at least partly by PGE(2).