Cutting edge:: Stromal cell-derived factor-1 is a costimulator for CD4+ T cell activation

Stromal cell-derived factor (SDF)-1 is a chemoattractant for T cells, precursor B cells, monocytes, and neutrophils. SDF-1 alpha was also found to up-regulate expression of early activation markers (CD69, CD25, and CD154) by anti-CD3-activated CD4(+) T cells. In addition, SDF-1 alpha costimulated proliferation of CD4(+) T cells and production of IL-2, IFN-gamma, IL-4, and IL-10, Stimulation with SDF-1 alpha alone did not induce activation marker expression, proliferation, or cytokine production by the CD4(+) T cells. SDF-1 alpha-mediated costimulation was blocked by anti-CXC chemokine receptor-4 mAb, RANTES also increased activation marker expression by anti-CD3-stimulated peripheral CD4(+) T cells, but less effectively than SDF-1 alpha did, and did not up-regulate IL-2 production and proliferation. These results indicate that SDF-1 and CXC chemokine receptor-4 interactions not only play a role in T cell migration but also provide potent costimulatory signals to Ag-stimulated T cells.