EN
Malignant glioblastomas are characterized by infi ltration of tumour tissue with brain macrophages that may consist up to 30% of tumour mass and contribute to tumour progression. A relative contribution of resident microglia and peripheral monocyte/macrophages in gliomas is poorly defi ned. We generated chimeric mice with the immune system reconstituted after irradiation with hematopoietic GFP-bone marrow cells. The dsRed-GL261 glioma cells were implanted to the brains of 16-weeks old C57BL/6 chimeric mice Two weeks after implantation, tumour bearing hemispheres were isolated and the number of CD11b+ CD45low microglial cells or CD11b+ CD45high macrophages was determined by fl ow cytometry. We found that peripheral GFP+ macrophages comprise above 60% of GFP+ cells in the tumor. A co-localization of Iba-1+ cells (macrophages/microglia) with GFP+ cells has been detected by confocal microscopy. Tumor associated peripheral macrophages can facilitate glioma invasion and promote angiogenesis. We have previously demonstrated that cyclosporin A (CsA) blocks activation of microglia and its promoting effects on glioma invasion in vitro and in vivo (Sliwa et al. 2007). In chimeric mice treated CsA, a percentage of GFP+ macrophages in gliomas was reduced suggesting an inhibitory effects of CsA on immune cell migration. Our studies demonstrate that blood-borne macrophages migrate to the tumour and consist a signifi cant population of tumour-associated macrophages.