Cdc42, Rac1 and INF2 are necessary for targeting of Lck to the plasma membrane in human primary T cells. (A) Human primary T cells expressing GFP and shControl or shRNA targeted to Rac1, Cdc42, INF2, or MAL from the same plasmid were fixed, permeabilized, and stained for Lck using anti-Lck antibodies and secondary antibodies coupled to Alexa-647. Note that Lck is almost exclusively detected at the plasma membrane in control primary T cells. (B) The histogram represents the mean percentage ± SEM of cells with an intracellular accumulation of Lck. Three independent experiments were performed; > 50 transfected cells were scored in each experiment (**P < .01). Scale bar indicates 5 μm.