Neely GG, Epelman S, Ma LL, Colarusso P, Howlett CJ, Amankwah EK, McIntyre AC, Robbins SM, Mody CH. Monocyte surface-bound IL-15 can function as an activating receptor and participate in reverse signaling.
J Immunol 2004;
172:4225-34. [PMID:
15034035 DOI:
10.4049/jimmunol.172.7.4225]
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Abstract
IL-15 is a short chain, four-alpha helix cytokine that shares some biological function with IL-2. One striking difference between IL-2 and IL-15 is the ability of monocytes to express IL-15 on their cell surface after activation. In the current study we have investigated the ability of human monocyte cell surface IL-15 to participate in reverse signaling. Cross-linking anti-IL-15 Abs were used as a surrogate ligand for surface IL-15 engagement. Ligation of cell surface-expressed IL-15 induced monocyte adhesion that required the activity of small m.w. GTPases. Reverse signals through surface IL-15 activated the Rho-GTPase Rac3. In addition, engagement of cell surface IL-15 was found to activate a number of signaling pathways, including both extracellular signal-regulated kinase 1/2 and p38, and resulted in the secretion of IL-8. IL-8 production required mitogen-activated protein kinase activity. Thus, the current study has established that cell surface IL-15 is more than just a ligand; it can function as a receptor and participate in reverse signaling that results in cellular adhesion and production of inflammatory cytokines.
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