Intrinsically altered lung-resident γδT cells control lung melanoma by producing interleukin-17A in the elderly.

Cancer is an age-associated disease, potentially related to the altered immune system of elderly individuals. However, cancer has gradually decreased incidence in the eldest globally such as the most common lung cancer, the mechanisms of which remain to be elucidated. In this study, it was found that the number of lung-resident gamma delta T cells was significantly increased with altered gene expression in aged mice (20-24 months) versus young mice (10-16 weeks). Aged lung V gamma 4(+) and V gamma 6(+) gamma delta T cells predominantly produced interleukin-17A (IL-17A), resulting in increased levels in the serum and lungs. Moreover, the aged mice exhibited smaller tumors and reduced numbers of tumor foci in the lungs after challenge with intravenous injection of B16/F10 melanoma cells compared with the young mice. Aged lung V gamma 4(+) and V gamma 6(+) gamma delta T cells were highly cytotoxic to B16/F10 melanoma cells with higher expression levels of CD103. The markedly longer survival of the challenged aged mice was dependent on gamma delta T17 cells, since neutralization of IL-17A or depletion of indicated gamma delta T cells significantly shortened the survival time. Consistently, supplementation of IL-17A significantly enhanced the survival time of young mice with lung melanoma. Furthermore, the anti-tumor activity of aged lung gamma delta T17 cells was not affected by alterations in the load and composition of commensal microbiota, as demonstrated through co-housing of the aged and young mice. Intrinsically altered lung gamma delta T17 cells underlying age-dependent changes control lung melanoma, which will help to better understand the lung cancer progression in the elderly and the potential use of gamma delta T17 cells in anti-tumor immunotherapy.