Neuronal interferon-gamma immunoreactive molecule: bioactivities and purification

An interferon (IFN)-gamma immunoreactive molecule, localized to small neurons in peripheral sensory ganglia (N-IFN-gamma), has been detected with two mouse monoclonal antibodies (DB1 and DB16) directed against different epitopes of rat IFN-gamma. To define N-IFN-gamma with regard to its protein characteristics and bioactivities, DB1 and DB16 were used to purify N-IFN-gamma from rat trigeminal ganglia in a two-step sequential antibody-affinity procedure. Sodium dodecylsulfate polyacrylamide gel electrophoresis (PAGE) and silver staining of purified N-IFN-gamma displayed three bands with an approximate molecular mass of 66, 62 and 54 kDa. The N-IFN-gamma bioactivity was confined to the protein stained on gel when native material was run on PAGE. Biological effects of pure N-IFN-gamma were examined and compared with those of lymphocyte-derived recombinant IFN-gamma. N-IFN-gamma had antiviral effects in vitro and induced major histocompatibility complex class I and II antigens on macrophages and in cells in skeletal muscle cell cultures. N-IFN-gamma also stimulated myoblast proliferation and affected cholinergic receptor distribution on myotubes similar to recombinant IFN-gamma. Both molecules potently stimulated Trypanosoma brucei brucei growth. These data suggest that, although N-IFN-gamma is a protein distinct from lymphocyte-derived IFN-gamma, the two molecules have enough structural similarities to allow for antibody recognition of at least two epitopes, and action on similar target structures on both parasite and mammalian cells.