Thymus atrophy during early pregnancy and its effect on a Trichinella spiralis infection in mice,including intestinal pathology and blood eosinophilia

The effects of pregnancy on the course of a $\text{Trichinella spiralis}$ infection and associated histopathological changes in thymus and small intestine were studied in outbred Swiss mice. For this purpose pregnant mice were orally infected with $\text{T. spiralis}$ on various days (1 to 8) $\text{post coitum}$. Virgin, age-matched infected and non-infected mice served as controls.Pregnancy induced a severe but reversible thymus atrophy, which was even more marked during a $\text{T. spiralis}$ infection. Thymus atrophy was most dramatic during mid and late pregnancy. During the involution phase a distinct increase in mast cells was observed.In animals infected during early pregnancy a not statistically significant inhibitory effect on worm expulsion was observed, whereas no effect was seen on the yield of muscle larvae, small intestine pathology (numbers of eosinophils, intestinal mast cells and globule leucocytes), blood eosinophilia and antibody production.Infection given during mid-pregnancy exerted an inhibitory effect on blood eosinophilia.On the basis of these results, it is concluded that although a severe atrophy of the thymus occurs during mid and late pregnancy, no effect on worm expulsion and intestinal pathology was observed when the infectious agent was given before thymus depletion started.