In vivo analysis of glial cell phenotypes during a viral demyelinating disease in mice

We stained mouse tissue with a mouse monoclonal IgM (04); fortunately, the inflammatory reaction did not confound our results. When 10 and 100 t~g/ml of nonspecific IgM (Calbiochem-Behring Corp., San Diego, CA) were applied to sections with processing as for 04 immunolabeling, we saw either no staining, or infrequently a diffuse signal lacking cellular structure. Rarely, bright oval cells were seen at the pia or in white matter; those cells, probably B lymphocytes, were also stained with the secondary antibody alone. Foamy macrophages, observed only in some specimens, were stained by 04 but not by nonspecific IgMs; these were easily recognized on morphological grounds and, as with the B lymphocytes, were excluded from descriptions presented here.