To further assess the effect of D1-receptor-expressing neurons stimulation in the medial shell of the nucleus accumbens on the function of CD8+ T cells, we next investigated the possible changes in the population of CD8+ T cells with the expression of immune checkpoint-related inhibitory receptors, such as programmed cell death protein-1 (PD-1), T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3) and Lymphocyte-activation-gene 3 (LAG-3), in the spleen of mice with tumor transplantation. The gene discussed is PDCD1; the disease is neoplasm.