Intradermal immunization in the ear with cholera toxin and its non-toxic β subunit promotes efficient Th1 and Th17 differentiation dependent on migrating DCs

The nature of CD4 ⁺ T-cell responses after skin immunization and the role of migrating DCs in the presence of adjuvants in the elicited response are interesting issues to be investigated. Here, we evaluated the priming of CD4 ⁺ T cells following ear immunization with low doses of model antigens in combination with either cholera toxin (CT) or the non-toxic β CT subunit (CTB) as an adjuvant. Following immunization with CT, we found efficient antigen presentation that is reflected in the production of IFN-γ and IL-17 by CD4 ⁺ T cells over IL-4 or IL-5 production. The CTB-induced activation of DCs in the ear occurred without visible inflammation, which reflects a similar type of CD4 ⁺ T-cell differentiation. In both cases, the elicited response was dependent on the presence of migrating skin cells. Remarkably, immunization with CT or with CTB led to the induction of a delayed-type hypersensitivity (DTH) response in the ear. The DTH response that was induced by CT immunization was dependent on IL-17 and partially dependent on IFN-γ activity. These results indicate that both CT and CTB induce an efficient CD4 ⁺ T-cell response to a co-administered antigen following ear immunization that is dependent on migrating DCs.