Ultrastructure, antigenicity, and histochemistry of stichocyte granules of adult Trichinella spiralis.

The stichosome of adult Trichinella spiralis was studied to determine its ultrastructural, antigenic, and histochemical characteristics. Stichocytes of adult worms had 2 types of granules, type I and type II, the ultrastructure of which was different from those of muscle larvae. Both types of granules consisted of a membrane surrounding a homogeneous matrix, and type I granules were rounder than type II granules. Sera from C3H mice immunized against excretory-secretory products of muscle larvae produced positive immunostaining of type I but not type II granules. Differences in antigenicity were observed between larval and adult stichocyte granules; monoclonal antibodies against alpha-granules of muscle larvae failed to label the adult granules. Azan staining revealed a histochemical difference between larval and adult stichocytes; adult stichocytes stained yellow, whereas larval stichocytes are known to stain red or blue. Thus, the present contribution revealed the existence of 2 distinct types of stichocyte granules in adult T. spiralis and showed them to differ profoundly from those characterized previously in muscle larvae.