APC and neoplasm: A dual role for IL-10 in the tumor microenvironment has been hypothesized: IL-10 is secreted constitutively by some tumors where it would have two major roles (1) to increase NK cell tumor killing, release of Ags and possibly APC uptake of damaged tumor cells and (2) to inhibit APC maturation with consequent maintenance of the ability to uptake Ags, remaining in situ rather than migrating to regional lymph nodes.