In marked contrast, neither chitin nor chitin + anti-PD-1 combination treatment reduced splenic myeloid cell numbers/percentages in the 66cl4-based model, resulting in similar splenic M1 and M2 macrophage subtype numbers/percentages (Fig. 8E, Additional file 15: Fig. S13D) and M1/M2 macrophage ratio (Fig. 8F) compared to spleens from untreated and anti-PD-1-treated 66cl4 tumor-bearing mice. This evidence concerns the gene PDCD1 and neoplasm.