Performance testing of antigen-coated polystyrene microplates for ELISA measurements of serum antibodies to bacterial and dietary antigens.

The adsorption of dietary antigens to polystyrene microplates was influenced by pH. Coating for 5 h at 37 degrees C followed by at least 18 h at 4 degrees C gave the best result with the six dietary and nine bacterial antigens tested in this study. Unwanted background activity was mainly caused by direct binding of human immunoglobulin in the second layer. This problem was mainly observed with coats based on antigens with relatively poor binding activity and could be reduced to an acceptable level by addition of 0.5% bovine serum albumin in the diluents. Microplates from various manufacturers showed large differences in antigen adsorbing properties and there were considerable variations among batches. Careful performance testing of microplates and selection of appropriate batches are therefore necessary.