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     Black line: Control Antigen (100 ng);Purple line: Antigen (10ng); Blue line: Antigen (50 ng); Red line:Antigen (100 ng)    

  
  

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     Flow cytometric analysis of HL-60 cells using CD307A mouse mAb (green) and negative control (red).    

  
  

CD307a, also known as FCRL5 (Fc receptor-like 5), is a transmembrane protein belonging to the Fc receptor-like family, predominantly expressed on B lymphocytes. It features extracellular immunoglobulin-like domains and cytoplasmic signaling motifs, enabling interactions with B-cell receptor (BCR) complexes. CD307a plays a dual role in immune regulation, modulating B-cell activation and tolerance through both activating and inhibitory signals. Its cytoplasmic region contains immunoreceptor tyrosine-based activation motifs (ITAMs) and inhibitory motifs (ITIMs), suggesting context-dependent regulatory functions.

This receptor is implicated in autoimmune diseases, such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), where dysregulated expression correlates with pathogenic autoantibody production. In malignancies like chronic lymphocytic leukemia (CLL) and lymphoma, CD307a may serve as a biomarker or therapeutic target due to its aberrant expression on malignant B cells. Research highlights its potential in immunotherapy, with anti-CD307a antibodies explored for targeting B-cell malignancies or modulating autoimmune responses. Additionally, CD307a's involvement in humoral immunity and germinal center reactions underscores its broader relevance in vaccine development and infection models. Ongoing studies aim to clarify its signaling mechanisms and therapeutic applications in precision medicine.