Antibody response in bronchoalveolar lavage and bile in rats after aerosol immunisation with an Escherichia coli strain producing ovalbumin.

We studied the expression of the antibody response in two parts of the mucosal immune system after exposing rats to an aerosol containing an Escherichia coli O6 strain which carries type 1 fimbriae and which is genetically manipulated to produce ovalbumin (OA). For comparison rats were immunised twice in the Peyer's patches (PP), 3 weeks apart, with the same bacteria. Bile, serum and bronchoalveolar lavage (BAL) were collected from both groups and the levels of antibodies directed against O6 lipopolysaccharide (LPS), type 1 fimbriae and OA were determined. The aerosol-exposed animals all developed higher levels of IgA anti-LPS antibodies in BAL than in bile. IgA antifimbrial antibodies were not detected in BAL despite the presence of such antibodies in the bile. Thus, the ratio BAL:bile was much higher for the anti-LPS antibodies than for the antifimbrial antibodies. This was in contrast to the PP-immunised animals which developed both IgA antifimbrial as well as anti-LPS antibodies in BAL although at a lower level than in bile and the ratios BAL:bile for the antibodies against fimbriae and LPS were similar. IgA anti-OA antibodies were present in bile from both groups but not detected in BAL in any group. IgG anti-LPS antibodies were very high in BAL and in serum in the aerosol-immunised animals, while neither IgG antifimbrial nor anti-OA antibodies were detected. The PP-immunised animals on the other hand developed IgG antibodies against both the fimbrial and the LPS antigens in serum but only against fimbriae in BAL.(ABSTRACT TRUNCATED AT 250 WORDS)