ABSTRACT
The importance of the mode of antigen presentation (intravenous, oral, or enteral restricted to the lower ileum) in the development of a local immune response and immunological memory for such a response in different parts of the intestine was studied in mice. Cholera toxin was used as antigen and the immune response was assayed by determining both the number of specific antitoxin-containing cells in the lamina propria and protection against experimental cholera. The results showed that all of these routes of antigen presentation could induce significant memory along the entire small intestine. In contrast, the actual production of antitoxin-containing cells or protective immune response elicited by booster immunization was restricted to those parts of the intestine that were directly exposed to antigen; i.e., lower ileum boosting resulted in immunity in the distal ileum but not in the proximal jejunum, whereas oral or intravenous boosting gave a response in both jejunum and ileum. Protection correlated closely with the number of antitoxin-containing cells in the lamina propria (correlation coefficient, 0.88); ≥4,000 antitoxin-containing cells per mm3 conferred solid immunity to cholera toxin-induced diarrhea. The total number of immunoglobulin-containing cells in intestines was not significantly influenced by the specific immunizations. There were four times as many of these cells in the upper jejunum (167,000 cells per mm3) as in the lower ileum, but the proportions of immunoglobulin A-containing cells (80 to 85%), immunoglobulin M-containing cells (14 to 20%), and immunoglobulin G-containing cells (0.4 to 0.9%) were similar in various parts of the intestine. The results indicate a differential dependence on local tissue antigen for the intestinal antibody-secreting cells and their memory cell precursors.
