Several studies have shown that social influences can penetrate remarkably deeply into our bodies. The nervous system plays a key role in perceiving and responding to social stimuli, and social conditions have been found to regulate the expression of neural genes such as the Nerve Growth Factor NGF gene (Sloan et al., 2007) and the glucocorticoid receptor gene (Zhang et al., 2006). More surprising is the discovery that key immune system genes are also sensitive to social conditions (Sloan et al., 2007). Immune cells exert selective pressure on the evolution of viral genomes, and many viruses also appear to have developed a genomic sensitivity to our social conditions (as reviewed above). However, even pathogens that escape our immune system may still modulate gene transcription in response to host stress and social conditions. Most human cancers are invisible to the immune system, but some still change gene expression patterns in response to social stress (Antoni et al., 2006). One recent study of women with ovarian cancer found more than 220 genes to be selectively up-regulated in tumors from women with low
