The nonreceptor tyrosine kinase Itk (interleukin-2 inducible T-cell kinase) is a member of the TEC-kinase family which encompasses Itk, Rlk, Btk, Bmx, and Tec. It is expressed mainly in immune cells such as T cells, mast cells, NK cells, and NKT cells. Alterations in Itk have been associated with human disorders. These include Itk promoter polymorphisms associated with atopy and the expression of an Itk-Syk fusion protein generated by a chromosomal translocation in T-cell lymphomas. Importantly, the implication of Itk in a human primary immunodeficiency has validated its role as a critical regulator of T lymphocyte function[1]. Mice lacking Itk exhibit impaired TH2 cytokine secretion; however, they have increased circulating serum IgE but exhibit few immunological symptoms of allergic airway responses[2]. Additionally, the use of RNA interference studies, kinase-inactive Itk mutants, and Itk small molecule inhibitors demonstrated that efficient uptake of HIV by CD4 + T cells and viral replication requires Itk kinase activity[3].