Macrophage innate training induced by IL-4 and IL-13 activation enhances OXPHOS driven anti-mycobacterial responses

MLE Lundahl, M Mitermite, DG Ryan, S Case… - Elife, 2022 - elifesciences.org
MLE Lundahl, M Mitermite, DG Ryan, S Case, NC Williams, M Yang, RI Lynch, E Lagan
Elife, 2022elifesciences.org
Macrophages are a highly adaptive population of innate immune cells. Polarization with
IFNγ and LPS into the 'classically activated'M1 macrophage enhances pro-inflammatory and
microbicidal responses, important for eradicating bacteria such as Mycobacterium
tuberculosis. By contrast,'alternatively activated'M2 macrophages, polarized with IL-4,
oppose bactericidal mechanisms and allow mycobacterial growth. These activation states
are accompanied by distinct metabolic profiles, where M1 macrophages favor near …
Abstract
Macrophages are a highly adaptive population of innate immune cells. Polarization with IFNγ and LPS into the ‘classically activated’M1 macrophage enhances pro-inflammatory and microbicidal responses, important for eradicating bacteria such as Mycobacterium tuberculosis. By contrast,‘alternatively activated’M2 macrophages, polarized with IL-4, oppose bactericidal mechanisms and allow mycobacterial growth. These activation states are accompanied by distinct metabolic profiles, where M1 macrophages favor near exclusive use of glycolysis, whereas M2 macrophages up-regulate oxidative phosphorylation (OXPHOS). Here, we demonstrate that activation with IL-4 and IL-13 counterintuitively induces protective innate memory against mycobacterial challenge. In human and murine models, prior activation with IL-4/13 enhances pro-inflammatory cytokine secretion in response to a secondary stimulation with mycobacterial ligands. In our murine model, enhanced killing capacity is also demonstrated. Despite this switch in phenotype, IL-4/13 trained murine macrophages do not demonstrate M1-typical metabolism, instead retaining heightened use of OXPHOS. Moreover, inhibition of OXPHOS with oligomycin, 2-deoxy glucose or BPTES all impeded heightened pro-inflammatory cytokine responses from IL-4/13 trained macrophages. Lastly, this work identifies that IL-10 attenuates protective IL-4/13 training, impeding pro-inflammatory and bactericidal mechanisms. In summary, this work provides new and unexpected insight into alternative macrophage activation states in the context of mycobacterial infection.
eLife