An immunoelectron micrograph of adult female worms

An immunoelectron micrograph of adult female worms including fetus and surrounding sheath, which are immunostained with infected sera taken from Fischer rats 32 weeks post infection with Trichinella spiralis, and secondary immunostained with anti rat IgG antibody (biotin tagged).  
The immunoreaction is visualised by the third reaction with avidin -gold complex.

    tissue         adult female worms
    1 st antibody    infected sera taken from Fischer rats
    2nd antibody    anti rat IgG antibody (biotin tagged)
    visual marker    colloidal gold   (avidin tagged)

The sheath is strongly positive by the immunostaining, suggesting the presence of antigen recognized by Fischer rats during the Trichinella infection.   

 
Similar positive staining is observed when anti phosphorylcholine antibody is used, suggesting the antigen is phosphorylcholin-related.
The fetus is negative by the immunostaining or very weakly positive if any.