Role of the Sympathetic Nervous System in Immunity

This chapter focuses on the association that exists between the SNS and the immune system. The sympathetic nervous system (SNS) plays a role in modulating the magnitude of a primary antibody response, suggesting one possible mechanism by which behavior might influence the level of immunity. Antigen exposure caused a change in the firing rate of neurons within the hypothalamus, which allowed activation of the SNS. The brain communicates with cells in the periphery through two well-characterized mechanisms: namely, the SNS and the neuroendocrine system. Radioligand binding analysis and pharmacological approaches confirmed that adrenergic receptors that bind norepinephrine (NE) are expressed on immune cells. These findings and many others set the stage for the establishment of an entirely new field of study focused on the role played by the SNS in modulating the immune response. Most immune cells express b2AR for NE, but that the Th2 cell represses expression as it differentiates from a naïve T cell. Engagement of b2AR on immune cells activates a cascade of distinct signaling intermediates that affect gene expression for certain antibody isotypes. And finally, b2AR-induced changes in CD86 gene expression on a B cell are associated with changes in CD86 function in the B cell, which is responsible for changes in immune-cell activity and function.