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.