CD4 and neoplasm: The authors found that, in the B16-F10 (melanoma) syngeneic mouse tumor model, an anti-PD-1 + BoNT/A1 combination treatment lowered the proportion of MDSCs, negated the increased proportion of Treg cells, and elicited a higher number of tumor-infiltrating CD4+ and CD8+ T lymphocytes into the tumor microenvironment compared to the anti-PD-1 treatment alone.