Immunomodulation of sheep and human lymphocytes by Fasciola hepatica excretory-secretory products.

Fasciola hepatica excretory-secretory (ES) products (30 micrograms ml-1 total ES protein upwards) significantly decreased tritiated thymidine (3HTh) uptake in phytolectin-stimulated sheep lymphocytes. Lower doses of ES products, however, caused an increase in 3HTh uptake in sheep cells stimulated with phytohaemagglutinin (PHA) and Concanavalin A (Con A) and, indeed, ES products were mitogenic on their own. In contrast, 3HTh uptake by human lymphocyte cultures in the presence of phytolectins was progressively inhibited by increasing doses of ES products, and ES products were not mitogenic on their own. The observed inhibitory effects on 3HTh incorporation were not due to toxicity of ES products.