The Reporter Antigen Popliteal Lymph Node Assay

Abstract Many chemicals, including drugs and environmental pollutants, may have the intrinsic capacity to stimulate or dysregulate immune responses. These responses may create considerable problems for exposed subjects in terms of development of autoimmunity or hypersensitivity reactions. The popliteal lymph node assay (PLNA) provides a suitable tool to assess the immunostimulating potential of chemicals and might be a potential candidate as a screening tool in immunotoxicological hazard identification. The use of so‐called reporter antigens (RA) in this assay additionally enables differentiation between immunosensitizing (sensitizers), immunostimulating (irritants), and innocent chemicals. In the RA‐PLNA, the compound of interest is injected into the hind footpad together with a nonsensitizing dose of the RA. After 6 to 8 days, RA‐specific responses are monitored in the draining PLN by measuring RA‐specific antibody formation, cytokine secretion, and shifts in immune cell numbers. Hence, this simple and straightforward assay provides immunologically relevant information about the immunomodulating properties of a chemical.