Role of microglia in glioma biology

Microglia, a type of differentiated tissue macrophage, are considered to be the most plastic cell population of the central nervous system (CNS). In r esponse to pathological conditions, resting microglia undergo a stereotypic activation process and become capable of phagocytosis, antigen presentatio n, and lymphocyte activation. Considering their immune effector function, i t is not; surprising to see microglia accumulation in almost every CNS dise ase process, including malignant brain tumors or malignant gliomas. Althoug h the function of these cells in CNS inflammatory processes is being studie d, their role in malignant glioma biology remains unclear. On one hand, mic roglia may represent a CNS anti-tumor response, which is inactivated by loc al secretion of immunosuppressive factors by glioma cells. On the other han d, taking into account that microglia are capable of secreting a variety of immunomodulatory cytokines, it is possible that they are attracted by glio mas to promote tumor growth. A better understanding of microglia-glioma int eraction will be helpful in designing novel immune-based therapies against these fatal tumors. (C) 2001 Wiley-Liss, Inc,