CD209 antigen-like protein B (SIGN-R1) (SIGN-R1)

CD209 antigen-like protein B, commonly known as SIGN-R1, is a type II transmembrane C-type lectin receptor primarily expressed on the surface of splenic marginal zone macrophages and lymph node medullary macrophages in mice [8, 11, 15]. It serves as a critical pattern recognition receptor (PRR) in the innate immune system, specialized in the recognition and capture of encapsulated pathogens such as Streptococcus pneumoniae and influenza viruses [3, 14]. Beyond its role in host defense, SIGN-R1 is a key mediator of the anti-inflammatory effects of high-dose intravenous immunoglobulin (IVIG) [1, 2]. It specifically binds to the alpha2,6-sialylated Fc fragments of IgG, initiating a regulatory signaling cascade that involves the release of IL-33 and IL-4, ultimately leading to the upregulation of inhibitory Fc receptors on effector cells [1, 2, 4]. Additionally, SIGN-R1 facilitates the systemic clearance of apoptotic cells by interacting with the complement component C1q, which is essential for maintaining immune tolerance and preventing autoimmunity [16, 18]. As a result, SIGN-R1 is a significant target for therapeutic strategies aimed at modulating inflammatory responses and enhancing pathogen clearance [1, 3].

Other names

CD209bOtB7DC-SIGN-related protein 1Specific ICAM-3 grabbing non-integrin-related 1

SIGN-R1 mediates the anti-inflammatory activity of intravenous immunoglobulin (IVIG) by binding to sialylated Fc regions, which triggers a regulatory cascade involving IL-33 and IL-4 that upregulates inhibitory FcgammaRIIB on effector macrophages [1, 2]. It also acts as a pattern recognition receptor for the clearance of encapsulated pathogens and apoptotic cells [3, 14, 16].