Model of NTM, BCG, and Mycobacterium tuberculosis immunologic interactions. A, BCG vaccination is usually administered at birth and NTM exposure occurs regularly throughout life via multiple routes with variable doses. These NTM-specific innate and adaptive immune responses may influence the response to BCG vaccination and susceptibility to M. tuberculosis. B, T-cell epitopes that are common between NTM and M. tuberculosis may mediate protective or deleterious immune responses: blue rectangle, T-cell epitopes that are shared between NTM and M. tuberculosis and lead to cross-protection between species; black rectangle, T-cell epitopes that are shared between NTM and M. tuberculosis but are not cross-protective and may impair immune responses to M. tuberculosis; pink rectangle, T-cell epitopes unique to NTM; red rectangle, T-cell epitopes unique to M. tuberculosis. Abbreviations: Mtb, Mycobacterium tuberculosis; NTM, nontuberculous mycobacteria; TB, tuberculosis; MP, macrophage; DC, dendritic cell.