Beyond polarization: a receptor-centered framework for macrophage function and therapy in skin diseases

Macrophages are key regulators of cutaneous immunity, but the traditional M1/M2 polarization model cannot fully explain their functional diversity across skin diseases. In this narrative review, we use selected skin diseases to discuss a receptor-centered view of macrophage function and to illustrate a modular "receptor-pathway-effector" framework. This perspective places macrophage receptors at the upstream sensing level, where microbial products, tissue damage signals, cytokines, immune complexes, stromal cues, and tumor-derived signals are translated into inflammatory, reparative, fibrotic, or immunosuppressive programs. We summarize representative receptor modules, including pattern-recognition receptors, cytokine and chemokine receptors, Fc and complement receptors, scavenger and efferocytosis receptors, and inhibitory checkpoint receptors. Across psoriasis, atopic dermatitis, autoimmune blistering diseases, lupus, systemic sclerosis, sarcoidosis, leprosy, melanoma, cutaneous T-cell lymphoma, diabetic wounds, and radiation-induced skin injury, these modules help explain macrophage involvement in inflammation, remodeling, host defense, impaired repair, and tumor immune escape. We also discuss selected biomarker and therapeutic examples, while distinguishing clinically explored approaches from preclinical or emerging concepts. This receptor-centered perspective may complement existing views of macrophage heterogeneity and provide a clearer way to link receptor signals with disease-related macrophage functions.