Evaluating the role of the αvβ3 and αvβ5 integrins in promoting microglial activation state in response to vitronectin. Wild-type, β3 integrin KO, β5 integrin KO and β3/β5 integrin DKO microglia were purified from mixed glial cultures as described in Materials and Methods, and then cultured in serum-free medium on vitronectin. After two days in culture, microglial expression of the activation marker MHC class I (panel A) or the α4, α5 and αM (Mac-1) integrin subunits (panel B) was analyzed by flow cytometry. All points in the graphs are expressed as the mean fluorescent index (MFI), and represent the mean ± SEM of three experiments. Note that all four strains of microglia expressed equivalent levels of the activation markers, implying that β3 integrin KO, β5 integrin KO and β3/β5 integrin DKO microglia had no defect in their activation response to vitronectin.