Follicular Dendritic Cell Secreted Peptide (FDCSP)

FDCSP is expressed by follicular dendritic cells (FDCs) and activated leukocytes during ongoing immune responses. The  protein is 45% identical to the mouse protein and contains an N-terminal signal peptide, followed by a conserved highly charged sequence and a moderately proline-rich central region. Northern blot analysis revealed abundant expression of a 0.5-kb transcript in tonsil, lymph node, and trachea, strong expression in prostate, and lower expression in thyroid, stomach, and colon, with weak or no expression in spleen, peripheral blood leukocytes, and bone marrow. No expression was detected in other tissues or in lymphoid cell lines. In situ hybridization and RT-PCR analysis showed strongest expression in the FDC-rich light zone of tonsillar germinal centers, but no expression in dark zone B cell-rich areas.