Therapeutic interventions that lead to enhanced activation of T cells in the tumor microenvironment (for example, interventions to reduce CD5) may be suitable components of combination therapy that include anti-CD5 treatment with immune checkpoint blockade: anti-CD5 would lead to increased PD-1 on tumor-resident T cells that, in turn, would lead to a situation promoting the effectiveness of anti-PD-1 immune checkpoint blockade. The gene discussed is PDCD1; the disease is neoplasm.