Therefore, our findings support the notion that autocrine (B-CLL cell-derived cytokines) and paracrine (IL-2, IL-4, IL-6, IL-10, IL-12, IL-15, IL-21, BAFF and APRIL from T cells, stromal cells, dendritic cells and Nurse-like cells) factors (Figure 5), and subsequent growth loops established by interactions of such cytokines may make large contributions to the progressive accumulation of B-CLL cells. The gene discussed is IL21; the disease is B-cell chronic lymphocytic leukemia.