Non-neuronal cells in the spinal cord of nude and heterozygous mice. II. Agranular leukocytes in the subarachnoid and perivascular space.

The lumbar spinal cord of the athymic nude mouse and its heterozygous control were examined at the light and electron microscopic levels for differences in the cellular constituents of the subarachnoid and perivascular spaces. Both macrophages and lymphocytes were found in these spaces associated with the adventitial and leptomeningeal cells. Occasionally, fixed-cells were associated with extensions of the basal lamina and subjacent astrocytic processes. The appearance of the basal lamina of the external glia limitans and perivascular space was enhanced by tannic acid treatment. There were twice as many macrophages as lymphocytes, but no significant strain differences. Comparison was made between cells in the lumina of incompletely perfused vessels and neuroglial cells in the spinal cord. The cellular morphology is distinct in each of these compartments and no cell migrations were observed between the blood, cerebrospinal fluid and C.N.S. interstitial space. The normal presence of both macrophages and lymphocytes in the subarachnoid and perivascular space suggests that these cells could penetrate the basal lamina and gain access to the C.N.S.