CX3CR1 and infection: Furthermore, in contrast to our hypothesis, infection with both Pb ANKA and Pb NK65 caused largely comparable activation of all three CX3CR1+/GFP populations with the most striking up-regulation of co-stimulatory (CD40 and CD80) and antigen presenting molecules (MHC-I) occurring in the CD45hiCD11bhi population (Fig 6E).