To more precisely determine where PbT-I cells were activated during the primary response to blood-stage PbA infection, B6 mice were injected with CFSE-labeled PbT-I cells one day before i.v. infection with blood-stage PbA, then various tissues were harvested 2 days later to examine expression of the early activation marker CD69 on PbT-I cells (Figure 2C, D). This evidence concerns the gene CD69 and infection.