Correlation between intestinal synthesis of specific immunoglobulin A and protection against experimental cholera in mice.

The importance of locally and systemically formed antibodies of various classes for protection against experimental cholera has been studied in mice immunized with cholera toxin. Groups of mice were given various numbers of peroral or intravenous immunizations, or a combination of both. Serum antibodies and antibodies synthesized by spleen and small intestine in vitro during tissue culture were measured by the enzyme-linked immunosorbent assay, and protective immunity against intestinal toxin challenge was determined by means of a small-bowel loop assay. Regression analyses showed a close correlation between the magnitude of intestinal synthesis of specific immunoglobulin A (IgA) antibodies and protection (r = 0.98), whereas neither the local formation of IgG or IgM nor the production of antitoxin antibodies of any immunoglobulin class by spleen showed any significant correlation with protection. The serum titers of IgG and IgM antibodies did not show any such relation, whereas the level of specific IgA in serum, probably mainly derived from the intestine, correlated significantly (r = 0.90).