Distribution and characterization of tumor-associated macrophages/microglia in rat C6 glioma

Immunity responses and immunotherapy are novel areas of research for the pathological development and treatment of glioma, the most common brain cancer. Characterization of the subpopulations of infiltrated immune cells may aid in our understanding of the tumor immune response and contribute to the identification of cellular targets for selective immunotherapy. Using a rat C6 glioma model, the present study observed a significant heterogeneity of active macrophages and microglia, including cluster of differentiation 8 (CD8)⁺, endothelial monocyte-activating polypeptide II (EMAPII)⁺ and ED1⁺ cells, mostly in the areas of compact tumor growth and inside or around the pannecrosis. Moreover, the CD8⁺ cells were similar to reactive ED1⁺ and EMAPII⁺ microglia/macrophages in morphology and distribution, but different from the W3/13⁺ T cells. These observations suggest that different subtypes of macrophages and microglia are involved in glioma development and thus, may be potential targets for immunotherapeutic antitumor strategies.