Student University of Arkansas for Medical Sciences, United States
Disclosure(s):
James Andrews: No financial relationships to disclose
Introduction/Rationale: Mycobacterium tuberculosis (Mtb) spends most of its lifespan within macrophages. During early infection, alveolar macrophages (AMs) facilitate rapid Mtb growth, whereas recruited monocyte-derived interstitial macrophages (IMs) restrict replication. However, macrophage subsets harboring Mtb in the presence of protective T cell–mediated adaptive immunity at the later stage of infection remain poorly defined. Many studies have relied on scRNA-seq to characterize macrophages without detailed phenotypic or functional analysis.
Methods: Our study aims to establish consensus on identifying lung macrophage subsets and analyze their dynamics and permissiveness across infection stages using high-dimensional flow cytometry and lineage tracing with scRNA-seq datasets.
Results: At 2 weeks post infection, CD11bhi AMs highly expressed CD63, CD38, and iNOS, consistent with a pro-inflammatory AM signature. Lineage tracing further confirmed the presence of monocyte-derived AMs. Four IM subsets were identified, with CCR2loCD11chiSca-1+ IMs being the predominant subset infected with Mtb. At 4 weeks post infection, six subsets of IMs were identified, and only three of them harbored Mtb. Notably, all three Mtb-infected IM subsets expressed high levels of CD11c, CD38, and iNOS.
Conclusion: These data provide a high-resolution analysis on heterogeneous lung macrophages and highlight shifts of their phenotypes during infection. It lays the foundation for future studies on how these macrophage alterations affect bacterial control.
