In the spleen of 4T1 tumor-bearing mice, the numbers/percentages of the lymphocytic subpopulations CD4+ and CD8α+ T-cells, B-cells, NK and NK-T cells significantly increased in response to chitin + anti-PD-1 combination treatment (Fig. 8G, Additional file 15: Fig. S13E). Here, PDCD1 is linked to neoplasm.