Involvement of IL-17A-producing TCR γδ T cells in late protective immunity against pulmonary infection.

Introduction: Interleukin (IL)-17A is a cytokine originally reported to induce neutrophil-mediated inflammation and anti-microbial activity. The CD4 T cells, which produce IL-17A, have been well characterized as Th17 cells. On the other hand, IL-17A-producing TCR γδ T cells have been reported to participate in the immune response at an early stage of infection with and in mice.

Essential role of IL-17A in the formation of a mycobacterial infection-induced granuloma in the lung.

Granulomas play an essential role in the sequestration and killing of mycobacteria in the lung; however, the mechanisms of their development and maturation are still not clearly understood. IL-17A is involved in mature granuloma formation in the mycobacteria-infected lung. Therefore, IL-17A gene-knockout (KO) mice fail to develop mature granulomas in the Mycobacterium bovis bacille Calmette-Guérin (BCG)-infected lung.