(A) The in vitro effect of IL-4 incubation on in vitro drug resistance to F-ara-a in human CLL cells. The cells were obtained from CLL patients after obtaining informed consent, isolated, and cultured at 1 × 10⁶/mL in medium (control) and varying concentrations of F-ara-A (0.01 to 100 μmol/L) in the absence (▪) or presence (▧) of IL-4 (10 ng/mL). After 4 days of incubation, the viability was assessed using the MTT test and is expressed for each patient as the LC₅₀ (drug concentration required to reduce viability by 50%). (B) The in vitro effect of IL-4 incubation on in vitro drug resistance to flavopiridol in human CLL cells. The cells were obtained from CLL patients after obtaining informed consent, isolated, and cultured at 1 × 10⁶/mL in medium (control) and varying concentrations of flavopiridol (0.01 to 100 μmol/L) in the absence (▪) or presence () of IL-4 (10 ng/mL). After 4 days of incubation, the viability was assessed using the MTT test and is expressed for each patient as the LC₅₀ (drug concentration required to reduce viability by 50%).