Cellular changes in the spleens of mice infected with Sarcocystis muris

Cellular changes in the spleens of mice infected with Sarcocystis muris have been studied. Immunofluorescent staining for B and T cells and alpha-naphthyl acetate esterase (ANAE) staining for macrophages combined with histological studies revealed marked changes in the populations and distributions of all three cell types. Infection was accompanied by a marked splenomegaly, attributable mainly to widespread hyperplasia of the white pulp. Following infection there was an increase in the relative proportions of B cells (i.e. surface immunoglobulin+) and ANAE+ cells and a decrease in the proportion of T cells (i.e. Thy 1.2+). There was also a progressive accumulation of immunoglobulin-containing cells in the periarteriolar lymphocytic sheaths. Splenomegaly was most pronounced 20 days after infection. At this time there were 9.3 times as many B cells, 3.7 times as many T cells and 16.6 times as many ANAE+ cells as in uninfected mice.