Abstract

Chicken antibodies were used to develop an ELISA for the quantitation of parts-per-million levels of protein A in the purification of immunoglobulins or immunoglobulin-like molecules. Quantitation of protein A in the presence of excess human or murine immunoglobulins in this assay was compared with that obtained in ELISAs developed with rabbit antibodies specific either to protein A or to other molecules. Experiments demonstrate that protein A is bound to the immunoglobulins being purified and that this binding affects subsequent recognition by the antibodies used for the assay. Because of these effects and because fragments of protein A might not be detected in assays which rely on Fc binding of protein A, chicken antibodies that bind protein A specifically are an advantage for the quantitation of this protein by ELISA. In addition, comparison of the effect of different types of immunoglobulins on the protein A standard curve suggests that alternatives to including the immunoglobulin under purification with the standards can be utilized.