ICOS and central nervous system cyst: The accumulation of CD8+ T cells to a T. gondii cyst detected in the brain of a recipient of WT CD8+ T cells is also shown in Figure 1F. These results indicate that although fewer ICOS−/− CD8+ T cells were present in the brains of the recipient SCID mice than WT CD8+ T cells were at 7 days after their transfer to the recipients, the former reduced the cerebral cyst burdens in the recipients as efficiently as or even more efficiently than the latter during 7 days after their transfer to the recipient mice.