Recently many investigations have been carried out which indicate possible link between the neuroendocrine and immunologic systems. The obtained information points out that some hormones not mentioned before can modify the immunological answer. More recently, the anterior pituitary hormone, prolactin, has been shown to have immune-stimulating properties through prolactin receptors, which are found an different cells. Among others prolactin receptors are present on B and T lymphocytes, monocytes and thomocyte epithelial cells. Immunological effects of this hormone were observed in vitro in investigations on animal experimental model and in humans. There are some therapeutic implications concerning patients with rheumatoid arthritis and with systemic lupus erythematosus and diagnostic implications, that determination of prolactin concentration in serum may appear to be useful marker of rejection in human heart transplantation. Although neuroendocrine regulations of immunological balance are complicated but by the regulation of prolactin secretion we can suspect the possibility of the control of autoimmunological diseases activity.