Involvement of excretion-secretion products from Fasciola hepatica inducing suppression of the cellular immune responses.

Normal rats i.p. injected with Fasciola hepatica excretor-secretor antigen (ESA) induced a population of spleen mononuclear (SpM) cells, which suppressed the delayed type hypersensitivity (DTH) response to parasite antigens as well as to non-related antigens (human serum albumin) by adoptive transfer. A similar effect was observed when the cell transfer was performed with SpM cells non-adherent to nylon wool. The DTH was not modified by cells transfer adherent to nylon wool in syngeneic receptor animals. The observed suppression depended on the concentration and inoculation moment of the antigen; 1.8 mg of protein ESA being enough to suppress the DTH response at the different days studied, before and after immunization with whole F. hepatica antigens. A marked suppression was observed when ESA was injected on day 7 pre-immunization. On the other hand, inoculation of ESA treated with 0.01 M sodium periodate (carbohydrate oxidant) diminished the suppressor effect found after the native ESA inoculation, indicating participation of ESA glucidic components in induced suppression. Inoculation of ESA fractions obtained from polyacrylamide gel elution with different MW range, showed that components between 12 and 23 kDa actively induced suppression to the DTH response to parasite antigens.