The endorphins are members of the proopiomelanocortin (POMC)-derived peptide family, which also includes adrenocorticotropic hormone (ACTH) and the melanocortins. The endorphins are produced by pituitary cells, neurons, and lymphocytes. The classical function associated with the endorphins, which includes alfa, beta, and gamma-endorphin. is anti-nociception. However, there is substantial evidence that the endorphins can modulate immune function through actions on lymphocytes. The actions of endorphins, whether centrally, peripherally, or on immune responses, are mediated through binding to opiate receptors which are expressed in various tissues, such as the brain and immune cells.