CHARACTERIZATION OF THE CIRCULATING T-CELL RESPONSE AFTER ORAL IMMUNIZATION OF HUMAN VOLUNTEERS WITH CHOLERA-TOXIN-B SUBUNIT

The kinetics and phenotypic characterization of the in vitro cell prol iferative response to the B subunit of cholera toxin were studied usin g peripheral blood mononuclear cells taken from human volunteers at fr equent time points after primary and booster oral immunizations. The c ells induced to proliferate by oral immunization secreted IL-3, and li popolysaccharide depletion and depletion of B cells did not affect pro liferation. Flow cytometry demonstrated that activated cells were CD3- and CD4-positive. These findings indicate primed T cells proliferatin g specifically to the B subunit. The kinetics of the response suggeste d trafficking in the peripheral circulation of primed T cells from the gut, with a peak stimulation index of between 7 and 93 after first im munization, and a precursor frequency of primed cells of between 1 in 25400 and 1 in 72390. There was close correlation between the serum an titoxin IgA antibody levels and observed proliferation.