IL15 and neuroblastoma: Under physiological conditions, IL-2 and IL-15 were at an extremely low level especially in NB patients (IL-2 0.44 ± 0.05 pg/ml in HC vs 0.27 ± 0.02 pg/ml in NB patients, p < 0.05; and IL-15 3.63 ± 0.6 pg/ml in HC vs 2.54 ± 0.39 pg/ml in NB patients, p = 0.18, respectively).