Mast cells and γδ T cells are largely dispensable for adaptive immune responses after laser-mediated epicutaneous immunization.

BACKGROUND: The skin resembles an attractive target for vaccination due to its accessibility and abundance of resident immune cells. Cells like γδ T cells and mast cells (MCs) are part of the first line of defence against exogenous threats. Despite being important mediators for eliciting TH2 immune responses after epithelial stress, γδ T cell and MC functions still remain to be completely understood. Here, we aimed to characterize their roles in shaping adaptive immune responses after laser-mediated epicutaneous immunization (EPI). METHODS: γδ T cell knock out, MC-depleted, and wildtype control mice were immunized with mannan-conjugated grass pollen allergen Phl p 5 (P5-MN) by laser-mediated EPI. After 2-3 immunizations, cytokine expression, T helper polarization, and antigen-specific IgG1/IgE levels were analysed. Furthermore, the local cytokine/chemokine milieu after laser microporation was determined. RESULTS: The majority of inflammatory chemokines and cytokines induced by laser treatment were not affected by the presence of γδ T cells or MCs. However, RANTES was elevated in γδ T cell knock out mice and GROα, TSLP, and IL-33 were significantly decreased after MC depletion. The absence of γδ T cells or depletion of MCs had no substantial effect on adaptive immune responses after laser-mediated EPI, except for slightly reduced IgG1 and effector T cell levels in MC-depleted mice. CONCLUSIONS: γδ T cells did not play a pivotal role in shaping the humoral and cellular adaptive immune response after laser-mediated EPI. MC depletion decreased the numbers of effector T cells, indicating a potential role of MCs in the activation and maturation of T cells after EPI.