Immune response of the ileum to invasive Escherichia coli diarrheal disease in rabbits.

We have previously characterized a rabbit model of invasive Escherichia coli diarrhea. The purpose of this study was to measure the in vitro synthesis of immunoglobulin and anti-invasive E. coli antibody by ileal tissue and levels of anti-invasive E. coli antibody in sera and ileal contents at intervals after diarrhea. Immunoglobulin synthesis by the ileum peaked at 7 to 9 days, but returned to normal by 11 to 13 days post-diarrhea.l Secretory immunoglobulin A (IgA) was synthesized in greater quantity than was IgG or IgM. Anti-invasive E. coli antibody synthesis peaked at 11 to 13 days, decreased to less than half of maximum by 21 to 24 days, but was increased again at 30 to 33 days post-diarrhea. Secretory IgA anti-invasive E. coli antibody was synthesized in greater quantity than was IgG or IgM antibody. Specific antibody of the IgG and IgM classes, but not of the IgA class, appeared in sera by 4 to 6 days and peaked at 7 to 15 days post-diarrhea. Secretory IgA anti-invasive E. coli antibody was detected in ileal contents by 7 to 13 days, but maximum levels were not reached until 50 to 55 days post-diarrhea. IgG and IgM anti-invasive E. coli antibodies were not detected in ileal contents. The synthesis and secretion of secretory IgA antibody were major components of the immune response of the ileum after infection with an invasive bacterium.