CD200R3, Mouse, mAb Ba103

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The monoclonal antibody Ba103 targets mouse CD200 Receptor-like 3 (CD200R3), a protein that appears as a 38 kDa monomer under reducing conditions and a 74 kDa dimer under non-reducing conditions. CD200R3, a single-pass type I membrane protein, likely forms a disulfide-linked dimer on cell surfaces.

Unlike the inhibitory CD200 receptor (CD200R), CD200R3 acts as an activating receptor within the immunoglobulin superfamily. It features a short cytoplasmic tail and a lysine residue in its transmembrane region, suggesting signaling through adaptor proteins like DAP12, DAP10, FcRg, or CD3z.

CD200R3 is predominantly expressed in the uterus and bone marrow-derived mast cells, and is also found in the spleen, lung, and myeloid cells such as dendritic cells, basophils, and mast cells. Its presence in the lungs of N. brasiliensis-infected mice highlights its role in immune responses. While generally weak in brain, testis, lung, and thymus, CD200R3 is most prominent in myeloid lineage cells, particularly mast cells and basophils, which are key players in allergic reactions and pathogen defense.

Ba103-induced basophil depletion underscores the crucial role of basophils in IgE-mediated chronic allergic inflammation. Furthermore, the antibody Ba103 can activate basophils ex vivo, cause systemic anaphylaxis in vivo, and trigger degranulation of MC/9 cells by cross-linking CD200R3. These features make CD200R3 and Ba103 valuable tools for exploring immune responses and allergic disease mechanisms.