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

Stromal cell-derived factor (SDF)-1 is a chemoattractant for T cells, precu rsor 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 pr oliferation 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. SD F-1 alpha-mediated costimulation was blocked by anti-CXC chemokine receptor -4 mAb, RANTES also increased activation marker expression by anti-CD3-stim ulated 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 t o Ag-stimulated T cells.