Bunn, K. E. | Search bioRxiv

bioRxiv2026

Evolution of the proinflammatory receptor TREM-1 in mammals reveals signatures of pathogen-driven conflict

Animal immune cells express a range of surface receptors that promote the detection of diverse host and pathogen-derived molecules. The triggering receptors expressed on myeloid cells (TREMs) encompass a family of cell surface receptors involved in the modulation of immune signaling cascades. Mammalian TREM-1 has emerged as a critical mediator of antibacterial immune defense and inflammatory disease, yet much remains unknown regarding its evolution and relevant molecular interactions. Here we applied a comparative phylogenetic approach to investigate patterns of divergence and natural selection among mammalian TREM-1 orthologs. We identify evidence of repeated positive selection acting within the extracellular ligand binding domain of TREM-1 among primates, rodents, and particularly bats. Structural simulations further suggest that genetic variation in TREM-1 impacts recognition of putative host and microbial ligands, with implications for downstream signaling functions. Together our findings identify patterns of rapid divergence in mammalian TREM-1, suggesting a history of evolutionary conflict in response to pathogen antagonism.

evolutionary biology↗

bioRxiv2024

Th2 cell extracellular vesicles promote eosinophil survival through the cytokine cargo IL-3 and prolong airway eosinophilia.

BackgroundExtracellular vesicles (EVs) mediate intercellular communication during immune responses. EVs are abundant in respiratory biofluids, and the composition of EVs in the lung changes during inflammation. ObjectiveWe aimed to quantify the contribution of T cells to airway EVs in allergic lung inflammation and ascertain their function during a type 2 inflammatory response. MethodsGenetic membrane tagging was combined with single vesicle flow cytometry to quantify T cell EVs in the airways of mice challenged with ovalbumin or house dust mite. EVs were purified from T helper type 2 (Th2) cell cultures and their functions on eosinophils assessed by flow cytometry and RNA sequencing. Th2 cell EVs were instilled into the lungs of mice to determine effects on lung eosinophilia. Finally, the function of an EV protein cargo was tested using inhibitors and blocking antibodies. ResultsT cell EVs are increased in the airways of mice with induced allergic inflammation. EVs secreted by Th2 cells inhibit apoptosis and induce activating pathways in eosinophils in vitro. This effect depends on re-stimulation through the T cell receptor. Th2 cell EVs prolong eosinophilia in vivo during allergic airway inflammation. Th2 cell EVs carry a potent form of the cytokine IL-3 on their surfaces, which inhibits apoptosis by activating Jak1/2-dependent pro-survival programs in eosinophils. ConclusionTh2 cell EVs promote eosinophil survival and prolong eosinophilia during allergic airway inflammation. This function depends on the EV cargo IL-3, supporting a role for EVs as vehicles of cytokine-based communication in lung inflammation. Key MessagesO_LIT cells secrete extracellular vesicles in the airway during allergic lung inflammation. C_LIO_LITh2 cell extracellular vesicles inhibit eosinophil apoptosis and prolong airway eosinophilia during allergic lung inflammation. C_LIO_LIIL-3 carried on Th2 cell EVs is a functional cargo, supporting a role for cytokine-carrying EVs as drivers of type 2 inflammation. C_LI Capsule summaryThis study supports that T cell extracellular vesicles may be important drivers of eosinophilic inflammation through the cytokine cargo IL-3, offering new insights into pro-inflammatory signaling in the allergic lung of patients with asthma.

immunology↗