Gardam, B.; Nam, E.; Kollis, P. M.; Kilyen-Coles, J.; Lenin, S.; Gliddon, B. L.; Tea, M. N.; Pitson, S. M.; Brown, M. P.; Ebert, L. M.; Gargett, T.

Background: Glioblastoma, while considered rare, is characterized by poor survival and few treatment advances for over 20 years. New treatment options for brain cancers are, therefore, desperately needed. Active research that is being conducted in immunotherapy for glioblastoma and other primary brain cancers may be hampered by the lack of detailed studies that characterize the different immune compartments of orthotopic murine brain tumor models. Methods: We used glioma neural stem cell lines derived from glioblastoma patients and murine glioma cell lines to produce intracranial xenograft and syngraft brain tumors in immunodeficient (NSG) or immunocompetent (C57BL/6) mice, respectively. High-parameter flow cytometry was used to characterize the immune cell compartment in each brain tumor model. We investigated the tissues of brain, spleen, lymph node, and bone marrow for the frequencies of monocytes, macrophages, B cells, T cells, dendritic cells, neutrophils, eosinophils, and where possible, their subsets. Results: In a study first of non-tumor-bearing mice, we show dramatic differences between NSG and C57BL/6 mice in numbers not only of T and B cells but also of other immune cells. Then we show in mice bearing brain tumors significant differences in numbers of immune cells in brain, draining lymph nodes, spleen and bone marrow. Also, we investigated the effects on immune cell numbers of luciferase-expressing murine glioma cell lines compared to the parental lines. Finally, we show the effects of whole-body irradiation on immune cell numbers. Conclusions: Our quantitative characterization of different immune compartments in orthotopic murine models of glioblastoma xenografts and syngrafts may allow for a better informed selection of tumor models that are appropriate for the pre-clinical investigation of immunotherapies for glioblastoma.