An enzyme-linked immunosorbent assay of anti-sheep red blood cell antibodies of the classes M, G, and A in the rat.

In order to investigate the immune system as a possible target for toxicity by chemicals, functional assays of the immune system are required. Sheep red blood cells (SRBC) are widely used as an antigen to study the immune competence of animals. Since routine toxicology includes data mainly provided with rat toxicity studies, there is a need for easy, specific, and reproducible assays of antibody responses to sheep erythrocytes in the rat. This report describes an enzyme-linked immunosorbent assay (ELISA) of anti-SRBC antibodies of the classes M, G and A in the serum of rats. Antigen preparations, prepared from ghosts of sheep erythrocytes by extraction with KCl, were used to coat the bottom of wells in 96 well microtiter plates. Serum samples from rats, that were immunized with sheep erythrocytes, were titrated on these plates, using specific polyclonal antibodies to rat immunoglobulins M and G, to which peroxidase was conjugated. Immunoglobulin A was assayed, using monoclonal anti-rat IgA antibodies, and polyclonal rat anti-mouse IgG that was conjugated with peroxidase. The results indicate that the ELISA of serum titers of IgM, G and A to sheep erythrocytes is an easy and reliable method, that can be used to detect the effects of chemicals on the immune system of the rat.