a 2014 study found that depriving mice of sleep increased cancer growth and dampened the immune system's ability to control cancers. the researchers found higher levels of m2 tumor-associated macrophages and tlr4 molecules in the sleep deprived mice and proposed this as the mechanism for increased susceptibility of the mice to cancer growth. m2 cells suppress the immune system and encourage tumour growth. trl4 molecules are signalling molecules in the activation of the immune system.