Specific immunosuppression by Trichinella: fine specificity and effect on lymphocyte function in vivo.

Muscle-phase Trichinella larvae depress the immune response of mice to the phosphorylcholine (PC)-bearing Trichinella antigen FCp without affecting responses to other PC-bearing or non-PC antigens. The depressive activity is independent of antigen dose and Trichinella species and, in adoptive cell transfer experiments with lethally irradiated recipient mice, depended on the state of the recipient (infected recipients had a depressed response even a month after their encysted larvae had been killed and regardless of whether the donor had been exposed to FCp) but not on the state of the transferred cells. We conclude that lymphocytes are not permanently altered by the depressive action, that the agent responsible persists in the host at least a month after the death of the encysted Trichinella larvae, and that the alteration does not eliminate lymphocyte immunological memory.