IL17-Producing γδ T Cells May Enhance Humoral Immunity during Pulmonary Pseudomonas aeruginosa Infection in Mice

The host acquired immune response, especially the humoral immunity, plays key roles in preventing bacterial pneumonia in the lung. Our previous research demonstrated that interleukin 17-producing gamma delta T cells (IL17-gamma delta, T cells) have a protective effect on the early innate immune response during acute pulmonary Pseudomonas aeruginosa infection. However, whether 1L17-gamma delta T cells also play a role in humoral immunity is unknown. In this study, an acute pulmonary gamma delta aeruginosa infection model was established in wild-type and gamma delta TCR-/- C57BU6 mice. The expression of IL-17 on gamma delta T cells isolated from infected lung tissues increased rapidly and peaked at day 7 after acute infection with P aeruginosa. Compared with wild-type infected mice, the levels of total immunoglobulins including IgA, IgG, and IgM in the serum and BALF were significantly decreased in gamma delta TCR-/- mice, with the exception of IgM in the BALE. Moreover, CD69 expression in B cells from the lungs and spleen and the level of BAFF in the plasma were also decreased in gamma delta TCR-/- mice. IL17-gamma delta T cell transfusion significantly improved the production of immunoglobulins, B cell activation and BAFF levels in gamma delta TCR-/- mice compared with gamma delta TCR-/- mice without transfusion; this effect was blocked when cells were pretreated with an IL-17 antibody. Together, these data demonstrate that IL17-gamma delta T cells are involved in CD19(+) B cell activation and the production of immunoglobulins during acute pulmonary P.aeruginosa infection. Thus, we conclude that IL17-gamma delta T cells may facilitate the elimination of bacteria and improve survival through not only innate immunity but also humoral immunity.