Appearance of hematogenous cells in the white matter of myelin-deficient Jimpy mice.

Various cells from the monocyte-macrophage line, a few neutrophils and some lymphocytes were found in the non-myelinated white matter of Jimpy mice, though there was no vascular injury to the brain parenchyma. Some of the lymphocytes appearing in the white matter were in close contact with macrophages, and occasionally with young oligodendrocytes. Such lymphocytes were mainly of the small type with few cell organelles in a scanty cytoplasm, though a few were of the medium type with a moderate amount of cell organelles in an enriched cytoplasm. Macrophages in the non-myelinated white matter displayed a highly heterogeneous cytoplasm. In particular, "cytoplasmic compartments" in macrophages displayed specific structures differing from the inclusion bodies generally seen in phagocytic cells. The contents of such "cytoplasmic compartments" were rather similar to parts of the macrophage's own cytoplasm, though they were isolated from the cytoplasm by a membrane and gaps. Our findings would seem to support the previous presumption that inherited myelin deficiency in Jimpy mice is induced by a T-cell mediated autoimmune response.