TEMPORAL AND SPATIAL CHANGES OF QUINOLINIC ACID IMMUNOREACTIVITY IN THE IMMUNE-SYSTEM OF LIPOPOLYSACCHARIDE-STIMULATED MICE

Quinolinic acid (Quin), a metabolite of tryptophan, is a neurotoxin th at has been implicated in a variety of neuropathologic disorders that have immune components. The goal of this study was to characterize the changes in the cellular localization of Quin immunoreactivity in a pa radigm of immune stimulation with lipopolysaccharide (LPS) in vivo to provide a basis for further studies on the physiological role of Quin in the immune system. Intraperitoneal LPS injection significantly incr eased Quin immunoreactivity (IR) in lymphoid tissues within 24 h. Spat ial changes in splenic Quin-IR demonstrated a shift from the periarter ial lymphoid sheaths to the follicles before returning to control leve ls by 72 h post-LPS. The strongly Quin-IR cells were tentatively ident ified as interdigitating dendritic cells and macrophages. Only minimal Quin-IR was detected in liver and lung, even under conditions of LPS stimulation combined with tryptophan loading. These data emphasize the temporally and spatially specific nature of Quin-IR changes in lympho id tissues under conditions of immune stimulation and raise the possib ility that Quin may have an immunomodulatory function.