Tec kinases regulate T‐lymphocyte development and function: new insights into the roles of Itk and Rlk/Txk

Summary:  The Tec (tyrosine kinase expressed in hepatocellular carcinoma) family of non‐receptor tyrosine kinases consists of five members: Tec, Bruton’s tyrosine kinase (Btk), inducible T‐cell kinase (Itk), resting lymphocyte kinase (Rlk/Txk), and bone marrow‐expressed kinase (Bmx/Etk). Although their functions are probably best understood in antigen receptor signaling, where they participate in the phosphorylation and regulation of phospholipase C‐γ (PLC‐γ), it is now appreciated that these kinases contribute to signaling from many receptors and that they participate in multiple downstream pathways, including regulation of the actin cytoskeleton. In T cells, three Tec kinases are expressed, Itk, Rlk/Txk, and Tec. Itk is expressed at highest amounts and plays the major role in regulating signaling from the T‐cell receptor. Recent studies provide evidence that these kinases contribute to multiple aspects of T‐cell biology and have unique roles in T‐cell development that have revealed new insight into the regulation of conventional and innate T‐cell development. We review new findings on the Tec kinases with a focus on their roles in T‐cell development and mature T‐cell differentiation.