APAF1 and Burkitt lymphoma: Based on the findings that small molecule-induced sensitization of primary BL cells was linked to the release of Apaf-1 from the membrane fractions to the S100 fractions and our previous study linking apoptosis resistance in B cell lymphoma cell lines to membrane sequestration of Apaf-1 [14], we next assessed the role of the membrane lipid rafts in the resistance of primary BL cells to drug-induced apoptosis.