Figure 2: Tec kinases structure and their differential roles The different members of the Tec kinase family are shown in a schematic. The proteins typically encode a N terminal pleckstrin homology domain (PH), followed by a Btk homology domain (BH), a proline rich region (PRR), a Src homology 3 (SH3) domain, a SH2 domain and a carboxy terminal kinase domain. Rlk, unlike the other members, encodes a palmitoylated string of cysteine residues on its amino terminal domain. Itk is expressed maximally in and is important for TH2 differentiation, while Rlk has a significant role in regulating TH1 cells. The role of Itk in TH1 cells is unclear, while Rlk may compensate for Itk function in Itk-/- cells. BMS-509744 is a pharmacological inhibitor of Itk.