Lung-resident CD3-NK1.1+CD69+CD103+ Cells Play an Important Role in Bacillus Calmette-Guérin Vaccine-Induced Protective Immunity against Mycobacterium tuberculosis Infection.

Tissue-resident immune cells play important roles in local tissue homeostasis and infection control. There is no information on the functional role of lung-resident CD3-NK1.1+CD69+CD103+ cells in intranasal Bacillus Calmette-Guérin (BCG)-vaccinated and/or Mycobacterium tuberculosis (Mtb)-infected mice. Therefore, we phenotypically and functionally characterized these cells in mice vaccinated intranasally with BCG. We found that intranasal BCG vaccination increased CD3-NK1.1+ cells with a tissue-resident phenotype (CD69+CD103+) in the lungs during the first 7 d after BCG vaccination. Three months post-BCG vaccination, Mtb infection induced the expansion of CD3-NK1.1+CD69+CD103+ (lung-resident) cells in the lung. Adoptive transfer of lung-resident CD3-NK1.1+CD69+CD103+ cells from the lungs of BCG-vaccinated mice to Mtb-infected naive mice resulted in a lower bacterial burden and reduced inflammation in the lungs. Our findings demonstrated that intranasal BCG vaccination induces the expansion of CD3-NK1.1+CD69+CD103+ (lung-resident) cells to provide protection against Mtb infection.

Metabolic changes enhance necroptosis of type 2 diabetes mellitus mice infected with Mycobacterium tuberculosis.

Previously, we found that Mycobacterium tuberculosis (Mtb) infection in type 2 diabetes mellitus (T2DM) mice enhances inflammatory cytokine production which drives pathological immune responses and mortality. In the current study, using a T2DM Mtb infection mice model, we determined the mechanisms that make T2DM mice alveolar macrophages (AMs) more inflammatory upon Mtb infection. Among various cell death pathways, necroptosis is a major pathway involved in inflammatory cytokine production by T2DM mice AMs. Anti-TNFR1 antibody treatment of Mtb-infected AMs from T2DM mice significantly reduced expression of receptor interacting protein kinase 3 (RIPK3) and mixed lineage kinase domain-like (MLKL) (necroptosis markers) and IL-6 production. Metabolic profile comparison of Mtb-infected AMs from T2DM mice and Mtb-infected AMs of nondiabetic control mice indicated that 2-ketohexanoic acid and deoxyadenosine monophosphate were significantly abundant, and acetylcholine and pyridoxine (Vitamin B6) were significantly less abundant in T2DM mice AMs infected with Mtb. 2-Ketohexanoic acid enhanced expression of TNFR1, RIPK3, MLKL and inflammatory cytokine production in the lungs of Mtb-infected nondiabetic mice. In contrast, pyridoxine inhibited RIPK3, MLKL and enhanced expression of Caspase 3 (apoptosis marker) in the lungs of Mtb-infected T2DM mice. Our findings demonstrate that metabolic changes in Mtb-infected T2DM mice enhance TNFR1-mediated necroptosis of AMs, which leads to excess inflammation and lung pathology.