In B16 melanoma and colon-26 carcinoma mice, maitake-derived α-glucan (a highly α-1,6-branched α-1,4 glucan, YM-2A) elevated the antitumor immune response through the up-regulation of INF-γ-expressing CD4+ and CD8+ T-cells in the spleen and INF-γ-expressing T-CD8+ cells in tumor-draining lymph nodes. The gene discussed is CD8A; the disease is neoplasm.