Co-culture with either NTL or CD40L cells proved even more cytoprotective for CLL cells (Figure 1A; P = 0.005 and P = 0.034 respectively); addition of IL-4 to these co-cultures did not further enhance the cytoprotection (NTL: P = 0.31, CD40L: P = 0.07). The gene discussed is IL4; the disease is B-cell chronic lymphocytic leukemia.