IL-12 as well as IL-2 upregulates CCR5 expression on T cell receptor-triggered human CD4(+) and CD8(+) T cells

The expression of chemokine receptors on leukocytes is related to their act ivation state. However, the exact mechanism underlying the induction of eac h chemokine receptor is poorly understood. Here, we investigated how CCR5, a chemokine receptor implicated in T cell trafficking and HIV infection, is induced in human T cells. CCR5 was marginally detected on a freshly prepar ed human peripheral blood mononuclear cell (PBMC) population. Long-term (8- day) stimulation of PBMC with IL-2 resulted in high levels of CCR5 expressi on on T cells. IL-12 failed to induce CCR5 on T cells in such a directly st imulated PBMC population. Stimulation of PBMC T cells with anti-CDS plus an ti-CD28 induced detectable albeit very low levels of CCR5 along with the in duction of IL-12 receptor. However, these TCR-triggered T cells expressed m uch higher levels of CCR5 when stimulated with IL-12. Although IL-2 also in duced CCR5 expression, CCR5 expression was more potent in IL-12 than IL-2 s timulation. These results indicate that, in addition to IL-2, IL-12 plays a n important role in the induction of CCR5 expression on T cells, particular ly TCR-triggered T cells.