Depression of cell-mediated immunity following inoculation of Trichinella spiralis extract in the mouse.

Mice pretreated with Trichinella spiralis extract (TsE), or infected with the parasite, rejected primary skin allografts in 18-23 days and secondary allografts in 12-16 days. Mice pretreated with saline or with bovine serum albumin (BSA) rejected the primary allografts in 12-18 days and did not accept the secondary grafts. Inoculation of increasing doses of parental spleen cells from mice pretreated with saline or with BSA in F1 hybrids produced proportionately stronger graft-versus-host reactions (GvHR) whereas increasing doses of cells from TsE pretreated mice reduced proportionately the capacity of the inoculum to induce a GvHR. Immunodepression of the parental cells was obtained with 7 and with 4, but not with 2, daily injections of TsE. The depression waned rapidly after the treatment with TsE but a significant degree still remained after 3 days. Immunodepression by TsE cannot be solely explained by antigenic competition and although our results are consistent with the induction of suppressor cells, it is probable that other mechanisms are also involved.