Immunomodulation by Trichinella spiralis: primary versus secondary response to phosphorylcholine-containing antigens.

The present work was designed to determine in detail the capacity of the nematode Trichinella to modulate the plaque-forming cell (PFC) response of BCF1 mice to the parasite's own antigens. To this end, we studied the PFC responses shown by infected and non-infected BCF1 mice using as the target antigen phosphorylcholine, an epitope which is found in the parasite. From the results presented here, the following conclusions can be drawn: i) Trichinella spiralis is capable of modulating the immunoresponse to thymus-dependent (TD), but not to thymus-independent (TI), parasite antigens; ii) Trichinella spiralis suppresses the PFC response to the parasite-derived TD antigen FCp1 (a particulate antigen containing PC) during the muscle stage of its life cycle, but does not affect the responses to other parasite-derived PC-bearing antigens; this seems to indicate that the suppressive activity exerted by Trichinella is highly specific; iii) anti-PC PFC production in the secondary response was also suppressed by the parasite. Finally, the inability of the FCp1 antigen to induce detectable anti-PC PFC, other than IgM, is discussed.