Immunoglobulin determinants on the surface of mouse splenic lymphocytes from Trypanosoma musculi-infected mice.

The splenic B-lymphocyte population of C57BL/6 mice was analyzed by flow microfluorometry to determine the relative density of surface immunoglobulin (sIg) during the course of infection with Trypanosoma musculi and after the injection of T. musculi derivatives. Cells were stained with fluorescent-conjugated antisera directed against 7S mouse immunoglobulins or the major sIg components, IgM and IgD. Evaluation of relative density of sIg was made through observation of histograms plotted by the Fluorescence Activated Cell Sorter (FACS). The FACS also provided the percentage of fluorescence-positive cells detected with each stain. The relative density of sIg was altered in all experimental groups as evidenced by abnormal histograms. These alterations in relative density of sIg persisted only on B cells of the trypanosome-infected and not the T. musculi-derivative-treated animals. The changes in sIg presumably resulted from sIgD modulation, because the histograms resulting from cells stained with anti-IgM remained unchanged. In the trypanosome-infected animals, there also was a reduction in the percentage of sIgD-positive cells near the end of the parasitemia. Observations of spleen sizes showed the same pattern of change with splenomegaly as with relative density of sIg. These data may be the result of the persistence of the parasite in host tissues after clearance of the blood infection.