In vitro stimulation with nontuberculous mycobacteria induced a stronger cytokine response in leukocytes isolated from individuals with latent tuberculosis compared to those isolated from active tuberculosis or cystic fibrosis patients.

Mycobacterium tuberculosis and opportunistic environmental non-tuberculous mycobacteria (NTM) can cause severe infection. Why latent tuberculosis infection advances to active disease, and why some individuals with cystic fibrosis (CF) develop pulmonary infections with NTM is still poorly understood. The aim of this study was to investigate the effector function of peripheral blood mononuclear cells (PBMC) from individuals with active or latent tuberculosis, individuals with CF with or without pulmonary NTM-infection and healthy controls, by measuring cytokine response to in vitro stimulation with different species of NTMs. The cytokine concentrations of IL-17A, IL-22, IL-23, IL-10, IL12p70 and IFN-γ were measured in PBMC-culture supernatants after stimulation with NTMs. PBMCs from individuals with latent tuberculosis infection showed strong IL-17A, IL-22, and IFN-γ responses compared to individuals with active tuberculosis or CF. IL-10 production was low in both tuberculosis groups compared to the CF groups and controls. This study suggests that IL-17A and IL-22 might be important to keep tuberculosis in a latent phase and that individuals with CF with an ongoing NTM infection seem to have a low cytokine response.