Follicular dendritic cell secretory protein(FDC-SP) is a protein generated by a follicular dendritic cell. FDCSP can bind to the surface of B cells whose gene lies on chromosome 4q13 adjacent to the clusters of proline-rich salivary peptides. Cysteine-X-Cysteine chemokine, which is adjacent to chromosome 4 open reading frame 7, not only regulates the antibody response and B cell chemotaxis but is also involved in the innate immune response. FDC-SP is expressed in the light zone of germinal-center leukocyte-infiltrated tonsil crypts by lipopolysaccharide(LPS), Staphylococcus aureus Cowan strain 1-activated leukocytes, or junctional epithelium in the oral cavity. FDC-SP is therefore significant in oral innate immunity. In addition, FDC-SP positively affects the proliferation of periodontal ligament cells and inhibits their differentiation into the mineralized tissue cells of fibroblasts through the epidermal growth factor receptor signal transduction pathway. As a specific biomarker of junctional epithelium in oral innate immunity, the expression of FDCSP is closely related to LPS level. Reports suggest that the periodontal health status and progress of periodontitis can be determined by the location or quantification of FDC-SP.
