M2-type markers

M2-type markers refer to molecular and cellular markers associated with the M2 phenotype of macrophages or microglia, which are key components of the immune system. These markers are used to identify macrophages that have adopted an anti-inflammatory, pro-repair, and pro-tumoral phenotype, as opposed to the M1 phenotype, which is pro-inflammatory and cytotoxic.

Overview of M2 Macrophages M2 macrophages are involved in tissue repair, angiogenesis, immune suppression, and tumor progression. Typically induced by cytokines such as IL-4, IL-10, and IL-13. Exhibit a protumoral role in the tumor microenvironment by suppressing immune responses and promoting tumor growth and metastasis. Key M2-Type Markers Surface Markers:

CD163: Hemoglobin scavenger receptor, highly expressed in M2 macrophages. CD206 (mannose receptor, MRC1): Involved in phagocytosis and endocytosis, commonly used to identify M2 macrophages. CD204 (scavenger receptor A): Plays a role in lipid metabolism and immune suppression. Cytokines and Chemokines:

IL-10: Anti-inflammatory cytokine secreted by M2 macrophages. CCL17 and CCL22: Chemokines that attract regulatory T cells (Tregs), promoting an immunosuppressive environment. TGF-β: Key cytokine for tissue remodeling and immune suppression. Transcription Factors:

STAT6: Activated downstream of IL-4/IL-13 signaling, crucial for M2 polarization. PPARγ: Regulates lipid metabolism and supports the M2 phenotype. Enzymes and Metabolic Markers:

Arginase-1 (ARG1): Converts L-arginine to ornithine, supporting tissue repair and suppressing NO production. Chitinase-like proteins (e.g., YKL-40/CHI3L1): Associated with tissue remodeling and repair. F13A1 (Coagulation Factor XIII A1): Linked to extracellular matrix stabilization and wound healing. Others:

VEGF: Promotes angiogenesis. MRC2 (Clever-1/Stabilin-1): Involved in extracellular matrix remodeling. Clinical and Research Relevance Cancer:

M2 macrophages contribute to an immunosuppressive tumor microenvironment, promoting tumor growth and metastasis. Strategies targeting M2 markers, such as CD206 or ARG1, are being investigated for cancer therapy. Chronic Inflammation and Fibrosis:

In diseases like liver fibrosis, M2 macrophages promote tissue scarring. M2 markers like CD163 and TGF-β are potential therapeutic targets. Neuroinflammation:

In brain disorders, M2-polarized microglia are involved in repair processes but can also contribute to neurodegeneration. Diagnostics:

M2 markers are used to characterize immune states in tissue samples, especially in tumors or inflammatory conditions.