Lymphocyte extraction Lymphocytes from peripheral blood were extracted using the ACK Lysing Buffer® (Life technologies, Grand Island, NY) kit. Briefly, a venous blood sample in EDTA tube (BD Vacutainer®, Franklin Lakes, NJ), was centrifuged at 3500 rpm during 5-8 minutes. The resulting intermediate white colored phase was extracted and placed in an eppendorf tube; 1 mL of ACK Lysing Buffer® was added and carefully re-suspended. Once again, the suspension was centrifuged at 3500 rpm during 5-8 minutes and the supernatant was discarded. This last step was repeated until the leukocyte package was completely white. Finally, it was added 100 mcl of ACK Lysing Buffer® and frozen at -70ºC for later use.