Neuropeptide Y inhibits in vivo specific antibody production in rats.

The sympathetic neurotransmitter neuropeptide-Y (NPY) is hypothesized to play a role in the in vivo modulation of immune responses. This study examined the effects of intraperitoneal administration of NPY on specific antibody responses to keyhole limpet hemocyanin (KLH) in rats. Antibody levels were repeatedly measured by enzyme-linked immunosorbent assay before and after intraperitoneal immunization with KLH. NPY induced a dose-dependent inhibition of IgM and IgG antibody responses following immunization with either physiologic or supraphysiologic doses of antigen. These in vivo results suggests that NPY may be involved in endogenous modulation of immune responses.