The effects of T. circumcincta infection on Tci - L4 - ES mediated lymphocyte suppression. Seven helminth-naïve lambs were trickle infected with 2000 T. circumcincta L3 three times a week for four weeks. PBMC were harvested at 0, 2, 4 and 6 weeks from the start of infection and cultured for 72 h with PBS alone (PBS), 5 μg/mL Con A (Con A + PBS) or 5 μg/mL Con A + 15 μg/mL Tci-L4-ES (Con A + ES). Proliferation was assessed at 72 h by measurement of [3H] thymidine incorporation. Levels of cytokine present in the cell culture supernatants at 54 h were determined by ELISA. (A) Faecal egg count (FEC) data over the course of the experimental infection. (B) Proliferation of PBMC in response to PBS, Con A + PBS and Con A + ES during experimental T. circumcincta infection. (C) Levels of serum Tci-L4-ES-specific IgA and IgG during experimental T. circumcincta infection. (D-F) Concentrations of IL-4, IL-10 and IFN-γ in PBMC cultures supernatants. Data represents mean ± SEM. a significant difference between Con A + PBS vs. PBS-stimulated cultures; b significant difference between ConA + ES vs. PBS-stimulated cultures; c significant difference between Con A + PBS vs. Con A + ES stimulated cultures; *P < 0.05, ** P < 0.01, ***P < 0.001 (repeated-measures two-way ANOVA followed by the Bonferroni post hoc test for comparison of means).