Abstract
Nontuberculous mycobacteria (NTM) cause pulmonary disease in individuals without obvious immunodeficiency. This study was initiated to gain insight into the immunological factors that predispose persons to NTM pulmonary disease (NTMPD). Blood was obtained from 15 pairs of NTMPD patients and their healthy household contacts. Peripheral blood mononuclear cells (PBMCs) were stimulated with the Mycobacterium avium complex (MAC). A total of 34 cytokines and chemokines were evaluated in plasma and PBMC culture supernatants using multiplex immunoassays, and gene expression in the PBMCs was determined using real-time PCR. PBMCs from NTMPD patients produced significantly less interleukin-1β (IL-1β), IL-18, IL-1α, and IL-10 than PBMCs from their healthy household contacts in response to MAC. Although plasma RANTES levels were high in NTMPD patients, they had no effect on IL-1β production by macrophages infected with MAC. Toll-like receptor 2 (TLR2) and TWIK2 (a two-pore domain K+ channel) were impaired in response to MAC in PBMCs of NTMPD patients. A TLR2 inhibitor decreased all four cytokines, whereas a two-pore domain K+ channel inhibitor decreased the production of IL-1β, IL-18, and IL-1α, but not IL-10, by MAC-stimulated PBMCs and monocytes. The ratio of monocytes was reduced in whole blood of NTMPD patients compared with that of healthy household contacts. A reduced monocyte ratio might contribute to the attenuated production of IL-1 family cytokines by PBMCs of NTMPD patients in response to MAC stimulations. Collectively, our findings suggest that the attenuated IL-1 response may increase susceptibility to NTM pulmonary infection through multiple factors, including impaired expression of the TLR2 and TWIK2 and reduced monocyte ratio. IMPORTANCE Upon MAC stimulation, the production of IL-1 family cytokines and IL-10 by PBMCs of NTMPD patients was attenuated compared with that of healthy household contacts. Upon MAC stimulation, the expression of TLR2 and TWIK2 (one of the two-pore domain K+ channels) was attenuated in PBMCs of NTMPD patients compared with that of healthy household contacts. The production of IL-1 family cytokines by MAC-stimulated PBMCs and MAC-infected monocytes of healthy donors was reduced by a TLR2 inhibitor and two-pore domain K+ channel inhibitor. The ratio of monocytes was reduced in whole blood of NTMPD patients compared with that of healthy household contacts. Collectively, our data suggest that defects in the expression of TLR2 and TWIK2 in human PBMCs or monocytes and reduced monocyte ratio are involved in the reduced production of IL-1 family cytokines, and it may increase susceptibility to NTM pulmonary infection.