Distinct IL-1 Receptor Signatures Separate Allergic and Autoimmune Inflammation
Interleukin-1 sits near the center of inflammatory biology, but its effects depend on more than the cytokine itself. Cellular responses are shaped by the balance between IL-1R1, the signaling receptor that drives pro-inflammatory cascades, and IL-1R2, the decoy receptor that binds ligand without transmitting a signal. In this study, that balance did not look the same in allergic and autoimmune disease. Peripheral blood immune cells from patients with bronchial asthma and rheumatoid arthritis showed disease-specific remodeling of IL-1 receptor co-expression, suggesting that the same cytokine family can leave very different cellular fingerprints depending on the inflammatory setting.
The cohort included 80 participants: 20 healthy donors, 23 patients with bronchial asthma, and 37 patients with rheumatoid arthritis. Fresh whole blood was analyzed by multicolor flow cytometry, allowing investigators to quantify receptor expression on 12 peripheral immune cell populations without first isolating mononuclear cells. That design preserved the circulating immune context and made it possible to examine receptor density, not just the presence or absence of a marker. Receptor abundance was measured as antibody-binding capacity per cell, a more granular readout than routine positivity alone.
A single theme ran through the data. The receptor landscape was not uniform across disease groups, and the differences were cell-subset specific rather than global in the simplistic sense.
Asthma Shifted Toward Receptor Loss and Double-Negative Cells
Bronchial asthma showed the most striking departure from the healthy pattern. Across most immune populations, the phenotype shifted toward cells that lacked both IL-1 receptors, with a profound reduction in decoy receptor expression. In practical terms, many circulating cells appeared to lose the inhibitory brake normally provided by IL-1R2, while also falling into a double-negative state on flow cytometric profiling. At the same time, naive T cells stood out for an opposite pattern: a striking predominance of the double-positive phenotype.
That combination is biologically interesting because allergic airway inflammation does not behave like a single-cell linear disorder. The airway immune response is shaped by chronic antigen exposure, repeated epithelial injury, and cytokine-driven recruitment of effector cells. A loss of IL-1R2 across several compartments could leave circulating cells more exposed to IL-1 signaling when ligand is present, while the double-positive naive T-cell signal suggests that early lymphocyte compartments may remain primed for intense cytokine responsiveness. In asthma, then, the IL-1 pathway appears redistributed rather than simply amplified or silenced.
The cohort also reflected clinically established disease heterogeneity. Patients with asthma were predominantly female, and the group included mild, moderate, and severe disease according to FEV1-based classification. Many were already receiving inhaled corticosteroid and bronchodilator therapy, and a substantial fraction had required corticosteroids during inpatient treatment. Even in that treated population, receptor remodeling remained detectable.
Rheumatoid Arthritis Showed a Different Pattern of Inflammatory Rewiring
Rheumatoid arthritis produced a separate signature. The shift toward double-negative cells was present, but less pronounced than in asthma. Decoy receptor loss was more selective, with monocytes showing the clearest reduction in IL-1R2. Cytotoxic T-cell compartments were mixed, yet signaling-competent phenotypes were preserved rather than globally erased.
This pattern fits the biology of autoimmune synovitis more closely than a diffuse allergic response would. In rheumatoid arthritis, persistent antigenic stimulation and myeloid activation dominate the inflammatory circuit, and monocytes are a plausible site for altered IL-1 sensing because they sit at the interface of innate activation and downstream tissue injury. Reduced decoy receptor expression on monocytes may permit stronger responsiveness to IL-1 family signals and help sustain the cytokine loops that feed joint inflammation, erosive disease, and systemic manifestations. The study population reflected that burden: most patients had erosive arthritis, and many had moderate to high disease activity by clinical grading and DAS-28 classification.
Naive T Cells, Monocytes, and Cytotoxic Compartments Did Not Behave Alike
The value of the analysis lies in its subset resolution. Naive T cells, monocytes, regulatory T cells, helper T cells, and cytotoxic T cells did not move in lockstep. Instead, each disease reorganized receptor co-expression in a way that matched its broader pathophysiology. Allergic inflammation favored a wider loss of decoy receptor expression across multiple compartments, while autoimmune inflammation produced a narrower but still meaningful shift centered on monocytes and selected T-cell populations.
This matters because IL-1 biology is controlled at several layers at once. Ligand processing, receptor signaling, receptor antagonism, and decoy sequestration all shape the final inflammatory output. When IL-1R1 and IL-1R2 are expressed together, absent together, or selectively lost, the immune cell’s threshold for activation changes. The clinical implication is not that one disease is simply “more inflammatory” than the other. It is that the route into inflammation differs, and the receptor architecture on circulating cells appears to reflect that divergence.
Exploratory Biomarker Models Pointed to Diagnostic Potential in RA
The investigators also tested whether receptor parameters could help separate disease groups from healthy controls. Unsupervised clustering and logistic regression suggested that the three cohorts could be distinguished by their IL-1 receptor profiles. For rheumatoid arthritis, a model using three parameters showed high discrimination in this case-control cohort, and its apparent and cross-validated performance remained robust within the study dataset.
That result is promising, but it remains exploratory. The study was not built as a clinical validation trial, and the model requires external testing before any use in practice. Even so, the data show that receptor co-expression carries more information than a single marker measured in isolation. A composite signature may capture disease state more faithfully because it reflects how inflammatory circuits are actually wired across immune subsets.
Why the IL-1 Pathway Looks Different in Allergic and Autoimmune Disease
The biologic explanation is plausible. Allergic asthma and rheumatoid arthritis both involve chronic inflammation, but they are not driven by the same dominant immune logic. Asthma is shaped by airway-centered allergic inflammation, repeated mucosal stimulation, and eosinophilic or mixed inflammatory activity. Rheumatoid arthritis is driven by synovial autoimmunity, myeloid activation, and persistent joint damage. IL-1 can participate in both, yet the cells that express its receptors and the way those receptors are balanced may depend on the inflammatory ecosystem surrounding them.
Age and treatment also deserve attention. Healthy donors in prior work showed age-related differences in IL-1 receptor expression, and many patients in this study were receiving anti-inflammatory or disease-modifying therapy. Those factors could influence receptor density, although the current analysis was not designed to disentangle each effect fully. The study still offers a useful map of what peripheral IL-1 receptor remodeling looks like in two clinically distinct chronic inflammatory diseases.
The most immediate limitation is straightforward: the cohort was small, single-center, and exploratory. External validation is still needed, and the receptor patterns observed here should be treated as candidate biomarkers rather than ready-made diagnostics. Even so, the cellular signal is clear enough to justify further study of how IL-1R1 and IL-1R2 shape chronic inflammation at the bedside and in future mechanistic work.