Biology subjects

Garnica, L.

Publications and source records attributed to Garnica, L..

4 recordsLinked to original sources

bioRxiv2026

Kinetics of local C3 production orchestrates neutrophil recruitment in lung injury

Complement component 3 (C3) is crucial for host defense against bacteria. While the liver is the primary source of circulating C3, local C3 production at barrier surfaces such as the lung is key in early responses. Yet, how local complement-mediated responses are initiated at mucosal barriers is unknown. This study investigates the kinetics and necessity of lung-derived C3 during the initial hours of an infection. Using models of bacterial pneumonia in ex vivo-perfused human lungs and mice deficient in liver-derived C3, we demonstrate that intrapulmonary C3 production and activation precedes the accumulation of circulating C3 into the bronchoalveolar space. Utilizing mice deficient in lung-derived C3, we demonstrate that epithelial cell-derived C3 is required for early neutrophil recruitment in pneumonia. Transcriptomic and proteomic analyses reveal that neutrophil chemotactic pathways such as C5a and CXCL2 depend on lung epithelial cell-derived C3. These findings demonstrate how lung epithelial-derived C3 influences early mucosal responses to infection via both canonical (direct) and non-canonical (indirect) pathways. SUMMARYAlburquerque et al show an initial, entirely local phase of complement-mediated mucosal protection before a subsequent, systemic response occurs in the setting of barrier disruption. Their work suggests that complement component C3 derived locally at a barrier from the epithelium influences early responses to infection by recruiting neutrophils via multiple pathways independent of circulating C3.

immunology↗

bioRxiv2024

Impaired complement regulation drives chronic lung allograft dysfunction after lung transplantation.

A greater understanding of chronic lung allograft dysfunction (CLAD) pathobiology, the primary cause of mortality after lung transplantation, is needed to improve outcomes. The complement system links innate to adaptive immune responses and is activated early post-lung transplantation to form the C3 convertase, a critical enzyme that cleaves the central complement component C3. We hypothesized that LTx recipients with a genetic predisposition to enhanced complement activation have worse CLAD-free survival mediated through increased adaptive alloimmunity. We interrogated a known functional C3 polymorphism (C3R102G) that increases complement activation through impaired C3 convertase inactivation in two independent LTx recipient cohorts. C3R102G, identified in at least one out of three LTx recipients, was associated with worse CLAD-free survival, particularly in the subset of recipients who developed donor-specific antibodies (DSA). In a mouse orthotopic lung transplantation model, impaired recipient complement regulation resulted in more severe obstructive airway lesions when compared to wildtype controls, despite only moderate differences in graft-infiltrating effector T cells. Impaired complement regulation promoted the intragraft accumulation of memory B cells and antibody-secreting cells, resulting in increased DSA levels. In summary, genetic predisposition to complement activation is associated with B cell activation and worse CLAD-free survival. BRIEF SUMMARYLung transplant recipients genetically predisposed to impaired complement regulation demonstrate worse chronic rejection-free survival. This phenotype is associated with intragraft B cell-activation and donor-specific antibodies.

immunology↗

bioRxiv2024

The C3-C3aR axis modulates trained immunity in alveolar macrophages

Complement protein C3 is crucial for immune responses in mucosal sites such as the lung, where it aids in microbe elimination and enhances inflammation. While trained immunity - enhanced secondary responses of innate immune cells after prior exposure - is well-studied, the role of the complement system in trained immune responses remains unclear. We investigated the role of C3 in trained immunity and found that alveolar macrophage C3 and C3aR1 expression increased in humans after an intranasal exposure to a training stimulus. In vivo, trained wild-type mice showed significantly elevated pro-inflammatory cytokines and increased C3a levels upon a second stimulus. Ex vivo, trained C3-deficient alveolar macrophages (AMs) displayed reduced chemokine and cytokine output as well as impaired phagocytosis and reactive oxygen species (ROS) production compared to wildtype AMs. Real-time confocal microscopy of live, intact mouse alveoli revealed that AMs internalize C3 rapidly after alveolar microinstillation, as compared to C3a. Correspondingly, the blunted cytokine output was restored by exogenous C3 but not by C3a. Inhibiting C3aR, both pharmacologically and with a genetic C3aR knockout, prevented this restoration, indicating the necessity of C3aR engagement. Mechanistically, trained WT AMs demonstrated enhanced glycolytic activity compared to C3-deficient AMs - a defect corrected by exogenous C3 in a C3aR-dependent manner. These findings reveal that C3 modulates trained immunity in AMs through C3aR signaling and highlight a novel role for C3 in trained immunity.

immunology↗

bioRxiv2022

Lung epithelial cell-derived C3 protects against pneumonia-induced lung injury

The complement component C3 is a fundamental plasma protein for host defense. However, recent work has demonstrated the critical importance of local C3 expression in cell survival. Here we analyzed the effects of local versus peripheral sources of C3 expression in a model of bacterial pneumonia. While mice with global C3 deficiency had severe pneumonia-induced lung injury, those deficient in liver-deficient C3 remain protected, comparable to wildtype mice. Human lung transcriptome analysis showed secretory epithelial cells are a major source of C3. Mice with a C3 gene ablation from lung epithelial cells had worse pulmonary injury compared to wild type, despite maintaining normal circulating C3 levels. Finally, in human cellular and mouse pneumonia models, we show that C3 reduces epithelial cell death mediated through the alternative pathway component Factor B. Thus, our findings suggest that a locally-derived C3-Factor B pathway protects the lung mucosal barrier. One Sentence SummaryLung-derived C3 mitigates severe bacterial pneumonia suggesting a novel cytoprotective role at mucosal barrier surfaces independent of circulating C3.

immunology↗