As an example of the spectrum of diseases caused by these downstream proteins, gain of function of ITK is common in T cell lymphomas (231), loss-of-function mutations are associated with lymphoproliferative diseases (232), full ITK deficiency has been linked to idiopathic CD4+ T cell lymphopenia (233), and SNPs in ITK have been associated with asthma (234). Here, ITK is linked to T-cell non-Hodgkin lymphoma.