Development and validation of a sensitive ELISA for quantification of secretory IgA in rat saliva and faeces

Non-invasive measures of immunological markers are an attractive means of s tress assessment in laboratory animals. Salivary IgA has been used successf ully as a stress marker in the human, and several reports indicate the pote ntial of secretory IgA as a non-invasive measure of stress in animals. The present paper describes the development of an ELISA using commercially avai lable components for the quantification of rat IgA and validation of this a ssay for the quantification of rat secretory IgA in saliva and faeces. The concentration of IgA in rat saliva varied significantly between duplicate s amples obtained from individual rats, and the viscosity and small total vol ume of rat saliva gave unsatisfactory results for IgA. Faecal IgA was prese nt in high concentrations, and duplicate samples varied by only 2-3 %. Howe ver, faecal IgA seemed less stable than IgA in other biological compartment s, and this finding must be taken into consideration when using quantitativ e measurements of IgA as a marker of mucous humoral immune status.