Intestinal antibodies in rats following exposure to live Vibrio cholerae

Indirect enzyme-linked immunosorbent assay methods were used to characterize the primary, secondary and tertiary antibody responses of rats to the lipopolysaccharide (LPS) and heat-sensitive surface-associated (HSSA) antigens of V. cholerae in the major immunoglobulin classes of serum, intestinal mucus and bile following intestinal injections of live organisms. Antibody production following the first injection was limited to the IgG and IgM classes of serum and the IgA class of bile but a second dose given 14 days later induced significant responses in all Ig classes of the three materials. Two contacts with the organism established effective, possibly long term, memory; large increases in serum IgG and intestinal mucus IgG and IgA anti-LPS antibody concentrations occurred when the organism was given 6 weeks later, but anti-HSSA production following the third injection was not significantly greater than during the secondary response. The results also suggest that while anti-LPS antibodies of all three Ig classes are formed in the intestinal lymphoid tissues, local anti-HSSA antibody is restricted to the IgA and IgG classes. Excretion of antibodies in bile does not directly correlate with responses in local and peripheral lymphoid tissues. It is suggested that the hepato-biliary system may be as important to antibody-mediated immunity in the intestine as are the active and passive transepithelial mechanisms of antibody secretion.