Gastrointestinal Antibody Responses inAxenicMiceto Topically Administered Escherichia coli

Immunoglobulin levels were determined ingastrointestinal secretions ofboth conventional andaxenic mice, as was thestability oftheimmunoglobulin classes inthese secretions. Axenic animals were thenadministered nonviable Escherichia coli O111:B4 bytopical application intothe oralcavity. Immunoglobulin (Ig) A,IgGl, andIgG2were detected inthegastrointestinal secretions, withan apparent gradation instability (IgA> IgGl> IgG2) undertheconditions investigated. Specific antibodies (IgAandIgG)toboththesomatic andthe flagellar antigens ofE.coli were demonstrated. Thetime courseoftheresponses tothepolysaccharide andprotein antigens suggested that a secondary response tolipolysaccharide was beingobserved inthesecretions. Examination ofthe autoclaved diet fedtothegermfree animals indicated thepresenceofantigenically intact polysaccharide materials (i.e., lipopolysaccharides), whereas anti