Immunohistochemical Study of CD68 and CR3/43 in Astrocytic Gliomas

Diffuse and high-grade astrocytomas are invasive neoplasms which grow diffusely into the brain parenchyma. Microglia has been termed the brain's immune system, although its specific role remains uncertain. Objective of this study was to assess in a series of astrocytic neoplasms, the expression of a macrophage marker CD 68 and Major Histocompatibility Complex Class II CR3/43. We examined 10 pilocytic astrocytomas, 13 diffuse astrocytomas and 17 anaplastic astrocytomas. For macrophages we used the CD68 monoclonal mouse antibody. For assessing the presence of MHC Class II complexes we used the specific monoclonal antibody CR3/43. CD68-positive mononuclear cells were observed in perivascular and hypoxic areas, within neoplastic tissue, inside and contiguous to vessel wall. CR3/43 positive complexes were detected in mononuclear elongated elements with amoeboid extensions strictly attached to endothelial cells, or contiguous to perinecrotic areas within neoplastic tissue. We suggest an active involvement of macrophage/microglia infiltrates in neovascularization and malignancy in astrocytomas. Macrophage infiltration and major histocompatibility complex class II complexes reactivity in gliomas could also suggest the occurrence of immune surveillance with a preliminary host's immune response. In addition, macrophages could promote angiogenesis mechanisms and induction of tumor growth.