Detection of Rheumatoid Factors of Different Isotypes by Elisa Using Biotinylated Avian Antibodies

An enzyme-linked immunosorbent assay (ELISA) using biotinylated avian antibodies has been developed for the detection of rheumatoid factors (RF) of various isotypes in human sera. The avian antibodies were obtained from the egg yolks of hens immunized with human IgA, IgG and IgM and were purified by affinity chromatography. These reagents made it possible to detect each of the three isotypes of RF present in the same serum and avoided false positives since the Fe epitopes of avian immunoglobulins are not recognized by the antibody combining site of RF.