CXCL8 and cyst: In spite of the great variability in cytokine concentration, glioblastoma cyst fluid levels of TNF-α, IL-6, IL-8, and CXCL1 were not significantly different from those in brain abscess pus, and, as stated above, the level of MCP-1 was significantly higher in cyst fluid, all indicative of a highly pro-inflammatory glioblastoma environment (Table 1).