Because RNA transcription shapes the protein complement of our cells, and those proteins mediate cellular function (Figure 1), psychological regulation of gene expression implies that the social world can remodel the functional characteristics of the human body. Consider the ability of chronic social stress to increase NGF gene expression, and thereby enhance the growth of SNS neural fibers in the lymph node tissues that structure immune responses (Sloan et al., 2007). This socio-environmental remodeling of lymph node innervation at Time1 can persist, providing a denser neural network through which subsequent stressful exposure at Time2 distributes SNS neurotransmitters into the lymph node. As a consequence, the immune system mounts a poorer response to viral infection at Time2 solely because lymph node innervation was remodeled by differing social conditions at Time1. In the model of Figure 3, social stress at Time1 (Environment1) is transmitted through the nervous system (Body1) into behavioral stress responses (Behavior1) and increased NGF gene expression (RNA1). Up-regulated NGF increases SNS innervation of the lymph node, and thereby alters the functional relationship between the nervous and immune systems (Body2).
