Fig. 1. Toxoplasma induces MØ PKB/Akt activation during in vivo and in vitro infection. (A,B) mice were i.p. infected with 10³ YFP-expressing RH tachyzoites. Eight days post-infection, spleen cells were isolated and subjected to staining with Ab to MØ marker F4/80 and phosphorylated-PKB (Ser473). (A) YFP expression in F4/80⁺ cells from infected animals. Inset shows lack of YFP signal in F4/80⁺ cells from non-infected mice. (B) Expression of phosphorylated-PKB (Ser473) in infected (YFP⁺, thick line) and non-infected (YFP^-, thin line) F4/80⁺ cells from infected mice described in A. Dotted line, isotype control. (C) Bone-marrow-derived MØs were infected with RH strain tachyzoites. Then, 15 minutes later, cells were collected for flow cytometric analysis. Cells were permeabilized and subjected to Ab staining for the tachyzoite surface protein p30 (SAG-1). The (a) non-infected and (b) infected populations (percentages are indicated) were examined for PKB expression (thick lines) relative to unstimulated cells (dashed lines). Thin lines in a and b show staining of secondary antibody alone on the total MØ population. Infected and non-infected cells gave the same level of background staining (data not shown). These experiments were repeated twice with the same result.