Immunofluorescence studies of the monocytes in the injured rat brain.

Rat brain was obtained on the 4th day after its damage by a stab wound. The injured and the normal control brain tissues were stained by the immunofluorescence technique using anti-granulomonocytic rabbit serum. After the fluorescence observation the same tissues were further stained by hematoxylin and eosin (HE) and studied comparatively by light microscopy. The following results were obtained: (1) The normal adult rat brain lacks the cells which react with the antiserum, thus the resting microglia occurring in the normal adult brain are antigenically different from the cells of the monocyte-macrophage system. (2) In the injured brain tissues monocytes extravasate, enter-brain parenchyma, and take ameboid forms or become macrophages. (3) Among the reactive cells in the injured brain, all of the brain macrophages and most of the ameboid cells were reactive with the antiserum thereby indicating their monocytic origin.