[Immunological reactivity to the products of normal microflora. III. Characteristics of antibodies to the common antigens of enterobacteria, enterococci and bifidobacteria].

The content and type of antibodies to the common antigens of enterobacteria, enterococci and bifidobacteria were studied in serum specimens obtained from 220 donors. Antibody titers to enterobacteria were almost twice as high as those to enterococci and 8 times higher than those in bifidobacteria. The final titer of the reaction with enterobacterial antigens in 90% of the donors was determined by IgG (7S); in respect of enterococci and bifidobacteria IgM played the leading role in 56% and 74% of the cases, respectively. In most cases the profile of immune responsiveness was characterized by marked individuality and comprised various titers and types of antibodies to the antigens of all three groups of bacteria. The results thus obtained are analyzed from the viewpoint of normal responsiveness to standard immunological stimuli; all individuals come in contact with such stimuli with an equal degree of probability.