The cells infiltrated in tumor-bearing p2rx7−/− contained an immunosuppressive microenvironment, compared to those growing in the wtAT background, with fewer effector T cells (Teff) (CD8+ and CD4+), increased Treg cells (CD4+, CD25+, Foxp3+) and a decline in cytotoxic effector CD8+ T cells (Tcyt). The gene discussed is CD8A; the disease is neoplasm.