Identification of E-coli K88 receptor in porcine intestinal mucus using anti-idiotypic antibodies

Escherichia coli K88 receptors were purified from porcine intestinal mucus by affinity chromatography using a K88 fimbrial antigen attached to Sepharo se 4B. Receptor eluate from the column was identified using anti-idiotypic antibodies that bore an internal image to K88. They were produced in chicke ns against both mouse anti-K88 monoclonal and rabbit anti-K88 polyclonal an tibodies. The anti-idiotypic antibodies were tested against purified recept ors using an indirect ELISA. Higher absorbance values (1.3 and 1.2) were ob served for the anti-polyclonal anti-idiotypic antibodies than those for ant i-monoclonal anti-idiotypic antibodies (0.95 and 0.56). Analysis of purifie d receptors by SDS-PAGE electrophoresis and immunoblotting with K88 fimbria e revealed several bands corresponding to 40, 45, 50 and 70 kDa. However, t he anti-polyclonal anti-idiotypic antibodies recognized only the 70 kDa pro tein while the anti-monoclonal anti-idiotypic antibodies failed to recogniz e any of these proteins. Sugar staining suggested that only the 50 kDa prot ein contained a sugar moiety. This study indicated that a 70 kDa protein in the intestinal mucus of pigs may be a dominant receptor for K88 and demons trated that anti-idiotypic antibodies are useful tools for receptor identif ication.