Interferon-gamma-like immunoreactivity in certain neurons of the central and peripheral nervous system

Interferon-gamma (IFN-gamma) has many important immunoregulatory functions. It has previously been presumed to be produced by activated lymphoid cells alone. The present study concerning the identification of IFN-gamma in neurons was initiated against the background that nerve function influences immunological events during inflammatory diseases. Furthermore, the immune system and the nervous system may have certain signal molecules as well as certain cell surface receptors in common. Neuronal IFN-gamma-like immunoreactivity (IFN-gamma-LI) was studied in frozen sections of rat tissues employing both rabbit polyclonal antiserum as well as seven different mouse monoclonal antibodies (mAbs) reactive with different epitopes of rat IFN-gamma. The polyclonal antiserum and three of the mAbs (DB-1, DB-14, and DB-16) showed IFN-gamma-LI in neurons. DB-1, the most extensively studied mAb, stained distinct networks of nerve terminal-like profiles both in the brain and spinal cord. Also, scattered brain neuronal cell bodies showed IFN-gamma-LI as well as a subpopulation of primary sensory ganglion cells and their intra CNS terminals. In addition, IFN-gamma-LI was also detected in nerve terminal-like profiles in skin, gut, and lymphoid organs. Terminals were especially prominent around blood vessels. We propose that IFN-gamma has a role in cell interactions not only in the immune system but also in the nervous system as well as in interactions between the nervous and immune systems.