Cholera toxin increases T lymphocyte responses to unrelated antigens

We have found that CT adjuvant greatly augmented oral priming immunizations. Limiting dilution analysis revealed strong increases in the frequency of primed antigen specific T lymphocytes subsequent to the use of CT adjuvant. Moreover, several fold stronger lymphokine production accompanied the strong proliferative responses seen with CT-treated and KLH-primed T cells. The lymphokine pattern secreted by these T cells suggested that TH1 as well as TH2 types of cells were effectively primed by KLH, and that CT adjuvant did not exert a selective effect on any of these T-cell subsets. These effects of CT were truly due to immunomodulation and not simply the result of a more efficient uptake of gut luminal antigens in the presence of CT, because CT enhanced equally well T cell priming by peroral as well as parenteral immunization with KLH. Moreover, the CT-induced enhanced responsiveness to antigen was also observed with CD4(+)-enriched T cells suggesting that CT primarily affected T cell priming rather than the balance between CD4+ and CD8+ T cell subsets.