In conclusion, our findings highlight that the patients with advanced melanoma treated with Nivolumab recorded, in dynamics, an increase in the number of CD8+ and NK cells in 85% and 79% of cases, respectively, while CD19+ cells had a decreasing variation in 79% of cases, but the values varied within normal limits, indicating a positive response of the immune system following the inhibition of PD-1 function. The gene discussed is CD19; the disease is melanoma.