Gel precipitation of common enterobacterial antigen by its antibody.

Abstract

Reinvestigation of the precipitation of the common enterobacterial antigen (CA) by its antibody revealed the following. (1) The precipitation in gel of CA by CA antiserum is characterized by a distinct arc-shape precipitation line close to the antiserum well. (2) Only CA antisera of high titer, as determined by hemagglutination, caused precipitation of CA in gel. However, not all antisera of similar hemagglutinin titer produced gel precipitation. (3) Concentration of CA antisera through collodion membrane increased the precipitating capacity of some CA antisera. (4) Various preparations containing the CA determinant were suitable antigens in this reaction, including the ethanolsoluble fraction of various <i>Enterobacteriaceae</i> and certain lipopolysaccharides. (5) The specificity of the reaction was documented by observing lines of identity with various CA-positive preparations and failure of precipitation of CA-negative preparations, including the ethanol-soluble fraction of <i>S. minnesota</i> Re 595, supernates of agar-grown cultures of <i>Staphylococcus</i> and <i>Pseudomonas</i>, certain lipopolysaccharides, and Vi antigen. (6) The precipitin line of CA by CA antibodies is distinctly different from those formed by·and Re-core antigen-antibody reactions.