CD8A and breast cancer: As for TLR2, the current TLR2 agonists such as polysaccharide krestin (PSK) extracted from mushrooms is being tested in a clinical phase II trial for the treatment of breast cancer due to its presumed immune potentiating effects.9 TLR2 agonists bind to TLR2 on antigen presenting cells (APCs) including dendritic cells (DCs) and macrophages, and initiate antigen presentation, costimulatory molecule expression, and cytokine secretion, thus activate antigen‐specific CD4 T cells and CD8 T cells, which develop cytolytic activity toward tumor cells.