Antibodies to quinolinic acid and the determination of its cellular distribution within the rat immune system

Antibodies to quinolinic acid were produced in rabbits with protein-conjugated and gold particle-adsorbed quinolinic acid. Quinolinic acid immunoreactivity was below detection limits in carbodiimide-fixed rat brain. In contrast, strong quinolinic acid immunoreactivity was observed in spleen cells with variable, complex morphology located predominantly in the periarterial lymphocyte sheaths. In the thymus, quinolinic acid immunoreactivity was observed in cells with variable morphology, located almost exclusively in the medulla. Lymph nodes and gut-associated lymphoid tissue contained many, strongly stained cells of similar complex morphology in perifollicular areas. Immunoreactivity in liver and lung was restricted to widely scattered, perivascular cells and alveolar cells respectively. Additional stained cells with complex morphology were observed in bronchus-associated lymphoid tissue, in skin, and in the lamina propria of intestinal villi. Follicles in all secondary lymphoid organs were diffusely stained, ranging from mildly to moderately immunoreactive in spleen, to intensely immunoreactive in gut-associated lymphoid tissue. These results suggest that quinolinic acid is an immune system-specific molecule. Two hypothetical schemes are proposed to account for high levels of quinolinic acid in specific cells of the immune system.