CD28 and neoplasm: Under the influence of IL‐4, tumor cells secrete IL‐10 which hinders activation and recruitment of adaptive immune mediators to the tumor microenvironment, by for example, downregulating CD28 expression, inhibiting proliferation and secretion of Th1 cytokines (IFNγ, TNF‐α, IL‐2) by T cells, as well as counteracting antigen presentation by dendritic cells.47, 48