Moreover, given that IL-4 is involved in the survival and proliferation of CLL cells, and T cell compartment in CLL is considered to be an important source of IL-4, our current results point to the possibility that, during CLL development, T cells acquire a unique ability to distort BTLA inhibitory function in order to maintain the longevity of malignant B cells. The gene discussed is IL4; the disease is B-cell chronic lymphocytic leukemia.