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Graham G Neely, Stephen M Robbins, Ernest K Amankwah, Slava Epelman, Howard Wong, Jason C L Spurrell, Kiran K Jandu, Weibin Zhu, Darin K Fogg, Christopher B Brown, Christopher H Mody, Lipopolysaccharide-Stimulated or Granulocyte-Macrophage Colony-Stimulating Factor-Stimulated Monocytes Rapidly Express Biologically Active IL-15 on Their Cell Surface Independent of New Protein Synthesis, The Journal of Immunology, Volume 167, Issue 9, November 2001, Pages 5011–5017, https://doi.org/10.4049/jimmunol.167.9.5011
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Abstract
Although IL-15 shares many of the biological activities of IL-2, IL-2 expression is primarily under transcriptional regulation, while the mechanisms involved in the regulation of IL-15 are complex and not completely understood. In the current study, we found that CD14+ monocytes constitutively exhibit both IL-15 mRNA and protein. IL-15 protein was found stored intracellularly and stimulation of CD14+ monocytes with either LPS or GM-CSF resulted in mobilization of IL-15 stores to the plasma membrane. This rapidly induced surface expression was the result of a translocation of preformed stores, confirming that posttranslational regulatory stages limit IL-15, because it was not accompanied by an increase in IL-15 mRNA and occurred independent of de novo protein synthesis. After fixation, activated monocytes, but not resting monocytes, were found to support T cell proliferation, and this effect was abrogated by the addition of an IL-15-neutralizing Ab. The presence of preformed IL-15 stores and the ability of stimulated monocytes to mobilize these stores to their surface in an active form is a novel mechanism of regulation for IL-15.
