Taenia multiceps (Cestoda): Ia antigen expression and prostaglandin secretion by parasite-modified, murine peritoneal macrophages.

Taenia multiceps secretions modify accessory cell activity in macrophages. The present experiments were designed to elucidate the cellular mechanisms involved. While normal, murine peritoneal macrophages amplified mitogen-activated T-cell proliferation, macrophages modified by exposure to parasite secretions inhibited this proliferation. The modified behaviour was shown by glutaraldehyde-fixed as well as living macrophages, and modification was inducible by FPLC fraction 24 of coenurus fluid and was associated with an expanded population of 1a- macrophages. Secretory products of parasite-activated macrophages also inhibited T-cell proliferation, and secretion was prevented by indomethacin. The measurement of modified accessory activity was not influenced by the concentration of tritiated thymidine in lymphocyte proliferation assays. Consequently there is no evidence that the reported events are affected by macrophage-derived, cold thymidine secretion. It is concluded that T. multiceps si able to manipulate macrophage accessory function by mechanisms which involve altered histocompatibility antigen expression and the secretion of prostaglandin.