ORAL-ADMINISTRATION OF ONE DOSE OF CHOLERA-TOXIN INDUCES A SYSTEMIC IMMUNE-RESPONSE PRIOR TO A MUCOSAL IMMUNE-RESPONSE BY A DIRECT PRESENTATION IN THE SPLEEN

In the present report the results indicate that the oral administratio n of one dose of CT in rats results in an antibody immune response in the spleen 48 h later, whereas no antitoxin antibody forming cells wer e found in the Peyer patches (PP), mesenteric lymph node (MLN) and lam ina propria (LP) of the small intestine. At this time the main isotype of the antitoxin antibodies in the spleen were IgG and IgM, 5 days af ter the priming, few antitoxin AFC were observed in the MLN, IgG being the main isotype, whereas no IgM antitoxin AFC were found. At 1 week after priming the number of antitoxin AFC in the MLN reached similar v alues to those observed in the spleen. When cells from the spleen of r ats primed orally with one dose of CT were cultured during 4 days in t he presence of inhibitory doses of anti-Ia MAb (OX6), the number of an titoxin AFC was diminished when compared with that observed when cells were cultured in the absence of anti-Ia. The main isotype of antitoxi n AFC observed when cells were analyzed after culture was IgM and it w as the isotype most affected by the treatment with MAb anti-Ia. These results strongly suggest that an in situ presentation of the antigen d id occur in the spleen. On the other hand, when the secondary immune r esponse was studied 48 h after boosting, antitoxin AFC were found in t he PP, MLN, SP and LP and 5 days after the booster a 20-30-fold increa se was observed in all lymphoid tissues studied, indicating that the s econdary immune response found in the spleen was mainly due to the rec ruitment of memory cells from Peyer's patches. However, when spleen ce lls were cultured 48 h after the immunization in the presence of inhib itory doses of anti-Ia a little decrease in the number of AFC was obse rved when compared with the controls (in absence of anti-Ia). The anal ysis of the antitoxin antibodies in sera and intestinal fluids were in line with the results presented above. The results shown in this repo rt indicate that the systemic immune response observed after the oral administration of CT could be due in part to an in situ presentation o f the antigen in the systemic compartments, especially in the spleen. Published by Elsevier Science B.V. All rights reserved.