B cells and humoral immunity have also been described to regulate anti-tumor immunity through other mechanisms, either by expressing cytokines, such as IL-10 or IL-35, inducing antibody-mediated cytotoxicity through NK cells, or by activating the C5a or C3a complement system components, which seem to either activate or suppress anti-tumor immunity in a context-dependent manner.424 However, the ways by which different B-cell types manifest their immunosuppressive effects remain poorly understood. Here, C5 is linked to neoplasm.