Characterization of perivascular cells in astrocytic tumours and peritumoral oedematous brain

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Abstract
Perivascular cells (PVCs) form an immunophenotypically defined population that plays an important scavenging role in the perivascular fluid drainage pathways in the rat brain; such cells may also act as antigen-presenting cells. The present study tests the hypotheses that (a) PVCs in human brain are distinct from microglia and haematogenous macrophages, and (b) PVCs within astrocytic tumours and peritumoral oedematous brain tissue react in a similar way to PVCs in the rat brain. Paraffin sections of formalin-fixed tissue from 10 astrocytomas, 10 anaplastic astrocytomas, 10 glioblastoma multiforme, peritumoral oedematous brain and from normal human brain were examined immunocytochemically using antibodies HLA-DR beta-chain for MHC class II antigen, PGM1 and MAC 387 directed against macrophage components, MT1 for T lymphocytes and GFAP for astrocytes. No PVCs, microglia or macrophages were labelled by these techniques in paraffin sections of normal brain. Microglia, macrophages recently derived from haematogenous monocytes and PVCs were labelled by immunocytochemistry in all tumours but were more numerous in glioblastomas than in astrocytomas or anaplastic astrocytomas. Perivascular cells were distinguished by their perivascular position, their expression of MHC class II antigen and were labelled by PGM1 antibody but not by MAC 387 antibody. Microglia and monocyte/macrophages, remote from blood vessels, on the other hand, were strongly labelled by MAC 387, moderately by PGM1 and showed weak expression of MHC class II antigen. A similar pattern of staining was seen in peritumoral oedematous tissue. These findings suggest that PVCs form a defined population of resident cells in the human brain and that they are distinct from microglia, monocytes and macrophages.(ABSTRACT TRUNCATED AT 250 WORDS)