Monoclonal antibodies specific for the phase-variant O-acetylated K1 capsule of Escherichia coli.

Two monoclonal antibodies, one each of the immunoglobulin M and G2b types, were produced from mouse spleen cells. These monoclonal antibodies only reacted with approximately 50% of the Escherichia coli K1 strains and not against group B meningococci. No reaction was observed after the strains were boiled. E. coli K1 strains that reacted with the monoclonal antibodies could become nonreactive after subculture. Based on these findings, we conclude that the monoclonal antibodies react with the O-acetylated K1 capsule.