Maternal to neonatal transmission of T-cell mediated immunity to Trichinella spiralis during lactation.

The potential of maternally derived cellular factors to mediate immunity to Trichinella spiralis in neonates during lactation was investigated in this study. Female FI rats, infected with T. spiralis, were able to transfer immunity to their suckling offspring, evidenced by a significant reduction in the intestinal parasite burdens of their neonates. When challenged between 2 and 3 weeks of age with 200 T. spiralis larvae, pups suckling on immune mothers harboured 28% and 26% (at 3 and 8 days post-challenge) of the worm numbers present in control neonates suckling on naive mothers. Cross-fostering experiments in which pups born of naive mothers but nursed by immune mothers showed significant immunity, demonstrated that this passage occurred through milk. The role of cell-mediated immunity in this immune transfer was analysed using T cells purified from MLN cells of syngeneic donor rats infected with T. spiralis. When 200 x 10(6) sensitized MLN T cells were adoptively transferred into lactating recipients, it led to the passive immunization of suckling neonates (26% and 13% of control values retained at 3 and 8 days post-challenge), while maternal injection of T cells primed to an irrelevant antigen (KLH) had no effect on neonatal immunity. Neonates fed per-orally with primed T lymphocytes early in lactation and prior to challenge were also rendered immune (34% and 44% of control values retained at 3 and 8 days post-challenge). A single dose of T. spiralis-primed T cells given to neonates in early lactation was sufficient to elicit a significant immune response in them at 2 weeks of age. These results support the hypothesis that cellular immunity mediated by antigen-specific T cells in milk can provide functional immune protection to the neonate against an intestinal pathogen.