In our previous studies, we proved the role of HLA class I expression and infiltration by several immune cell types (e.g., CD4+ and CD8+ T lymphocytes, regulatory T cells, B lymphocytes, NK cells, CD68+ macrophages, PD-1+ and CD134+ lymphocytes) in predicting responses to treatment and/or the survival of melanoma patients receiving ipilimumab therapy [25,26]. The gene discussed is CD4; the disease is melanoma.