Exogenous IL-2 does not negatively regulate expression of endogenous mouse CX3CR1 in vivo. (A) Freshly isolated bone marrow, splenocytes, and PBMCs from PBS-injected (PBS), IL-2-injected (IL-2), and noninjected (nil) C57Bl/6 mice were examined for CX3CR1 protein expression 1, 5, and 7 days after injection using methods identical to those for Figure 5. (B) Results in panel A were quantitated by densitometry. Protein analysis was performed on samples pooled from 5 mice in each group, to have sufficient material for protein analysis in the PBMCs.