THE BONE-MARROW AS A SITE OF ANTIBODY-PRODUCTION AFTER A MUCOSAL IMMUNIZATION

To study the importance of the bone marrow in the production of specif ic antibodies after a mucosal immunization with cholera toxin, the IgG , IgA and IgM specific antibody forming cells were evaluated by ELISPO T in Peyer patches, mesenteric lymph node (MLN), spleen, blood and bon e marrow (BM). When 50-day-old rats were immunized intra-Peyer patches , a similar number of IgG and IgA antitoxin antibody forming cells (AF C) were found in the BM, whereas in the other lymphoid tissues a highe r number of IgG antitoxin was found. In all sites the peak of AFC was obtained 2 weeks after immunization. The administration of CT to 35-we ek-old rats resulted in a stronger immune response in all lymphoid tis sues studied, but the proportion of antitoxin AFC contributed by the B M had not changed. One oral dose of cholera toxin resulted in a low nu mber of antitoxin AFC, whereas when two or three doses of CT were admi nistered orally an increase in the number of AFC was observed in the B M, reaching similar or higher numbers of IgG and IgA AFC than in the s pleen. In all cases the highest number of AFC/10(6) cells was observed in the MLN, whereas antitoxin AFC were not found in the blood. The to tal number of AFC recovered from each organ was calculated taken into account that the BM of one femur represents 9% of the total BM. So, it was found that the BM is an important site in the production of IgG a ntitoxin antibodies, being the main site in the IgA antitoxin antibody production.