Temporal and spatial changes of quinolinic acid immunoreactivity in the immune system of...

Quinolinic acid (Quin), a metabolite of tryptophan, is a neurotoxin that 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 paradigm 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 increased Quin immunoreactivity (IR) in lymphoid tissues within 24 h. Spatial changes in splenic Quin-IR demonstrated a shift from the periarterial lymphoid sheaths to the follicles before returning to control levels by 72 h post-LPS. The strongly Quin-IR cells were tentatively identified 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 lymphoid tissues under conditions of immune stimulation and raise the possibility that Quin may have an immunomodulatory function.