Similarly, the frequency of OX40L positive cells varied among FAB subclasses, with a tendency to higher expression in subjects presenting with acute promyelocytic leukemia (FAB M3) and mature leukemia (FAB M5) and a significantly higher expression in FAB M3 compared to FAB M1 (Fig. 2b). The gene discussed is TNFSF4; the disease is acute promyelocytic leukemia.