tokens: Recent data from mice deficient for phosphatase and tensin homologue deleted from chromosome 10 or src homology 2 domain-containing 5 ' inositol phosphatase , phosphatases that negatively regulate the phosphatidylinositol 3-kinase ( PI3K ) pathway , revealed an increased number of macrophages in these animals , suggesting an essential role for the PI3K pathway for macro-phage survival .