Fig. 3.

Immune modulation by CSCs. CSCs can alter tumor-associated immunity by secretion of factors that directly and indirectly suppress immune responses. For instance, several factors secreted by CSCs recruit TAMs, which subsequently suppress adaptive immune responses. Some factors have been found to inhibit natural killer cell and dendritic cell responses. CSC-derived factors can also directly affect T cell responses, leading to expansion of regulatory T cells or inhibition of cytotoxic T cells. Effects of specific cytokines are described in more detail in Table 2.