ICOS and cyst: Consistently, further analyses using real-time reverse transcriptase PCR (RT-PCR) on the brains of SCID mice that had received CD8+ T cells from uninfected or infected WT mice revealed that four genes, ICOS, CXCR3, CXCR6, and IL-18R1, among the 6 genes were significantly upregulated in the brain of the immune T cell recipients compared to normal CD8+ T cell recipients in which the cyst elimination did not occur.