Gitter cells and their relationship to macrophages in the developing cerebellum: an electron microscopic study.

The whole heads of 6 days old rats were exposed to 150R of X-ray irradiation. The animals were sacrificed in a developmental sequence, and the tissue obtained from the cerebellum was prepared for electron microscopy. In the medullary layer of the cerebellum of normal animals resting macrophages could be identified. On the basis of the cytological criteria established in the control material transformation of resting macrophages into reactive macrophages was studied. They showed an increase in the cytoplasm, which acquired numerous vacuoles, and changes in the breakdown and distribution of the large clumps of heterochromatin in the nucleus. The former changes gave these cells a lattice-like appearance, and the latter changes an appearance identical to that of the reactive macrophages in the brains of the neonate animals and the reactive microglia in the adult brains. The transformed macrophages in the medullary layer were identified as gitter cells. Issues pertaining to the relationship between gitter cells, reactive phagocytic cells, and resting macrophages are discussed, and factors stimulating the resting macrophages are considered.