[Neuropeptides, endogenous opioid peptides and cell proliferation].

Neuropeptides are oligo- or polypeptidies having a number of common features including biosynthesis, metabolism and biological effectiveness at extremely low concentrations. They function as cotransmitters in the central, peripheral and autonomic nervous system. As autocrine, paracrine, neurocrine or endocrine factors, neuropeptides also directly modulate functions of many types of cells in different tissues, including the lymphoid tissue. Neuropeptides influence cell proliferation and differentiation. Those functions are accomplished by neuropeptide binding to specific receptors. Recent studies emphasize the participation of neuropeptides in the control of organogenesis in embryonal, fetal and early postnatal periods as well as in tumor growth control. The family of neuropeptides includes endogenous opioid peptides, found in nervous and many other tissues. Lymphoid and hematopoietic tissues produce opioid-like oligopeptides, and the membrane marker CD10/CALLA (enkephalinase) expressed on lymphoid, myeloid and stromal bone marrow cells functions as an enzyme processing the enkephalins and other neuropeptides. It might be assumed therefore that opioid peptides participate among other cytokines in the regulation of hematopoiesis.