Interleukin-15 enhances proliferation and chemokine secretion of human follicular dendritic cells.

The germinal centre (GC) is a specialized microenvironment where high-affinity antibodies are produced through hypermutation and isotype switching. Follicular dendritic cells (FDCs) are the stromal cells of the GC. The timely expansion and establishment of an FDC network is essential for a protective GC reaction; however, only a few factors modulating FDC development have been recognized. In this study, we report that interleukin-15 (IL-15) enhances human primary FDC proliferation and regulates cytokine secretion. The FDCs express IL-15 receptor complexes for IL-15 signal transduction as well as for specific binding. Moreover, the secretion of chemokines CCL-2, CCL-5, CXCL-5 and CXCL-8 was reduced by blocking IL-15 signalling while the secretion of other cytokines, and the expression of CD14, CD44, CD54 (ICAM-1) and CD106 (VCAM-1) proteins remained unchanged. These results suggest that IL-15 plays a crucial role in the development of FDC networks during GC reaction, offering a new target for immune modulation.