LFA-1 Ligation by High-Density ICAM-1 Is Sufficient To Activate IFN-? Release by Innate T Lymphocytes.

ABSTRACT: By binding to its ligand ICAM-1, LFA-1 is known to mediate both adhesion and costimulatory signaling for T cell activation. The constitutively high LFA-1 cell surface expression of invariant NKT (iNKT) cells has been shown to be responsible for their distinctive tissue homing and residency within ICAM-rich endothelial vessels. However, the functional impact of LFA-1 on the activation of iNKT cells and other innate T lymphocyte subsets has remained largely unexplored. In particular, it is not clear whether LFA-1 contributes to innate-like pathways of T cell activation, such as IFN-? secretion in response to IL-12. Using a recombinant ICAM-1-Fc fusion protein to stimulate human iNKT cells in the absence of APCs, we show that LFA-1 engagement enhances their IL-12-driven IFN-? production. Surprisingly, exposure to high densities of ICAM-1 was also sufficient to activate iNKT cell cytokine secretion independently of IL-12 and associated JAK/STAT signaling. LFA-1 engagement induced elevated cytoplasmic Ca2+ and rapid ERK phosphorylation in iNKT cells, and the resulting IFN-? secretion was dependent on both of these pathways. Analysis of freshly isolated human PBMC samples revealed that a fraction of lymphocytes that showed elevated LFA-1 cell surface expression produced IFN-? in response to plate-bound ICAM-1-Fc. A majority of the responding cells were T cells, with the remainder NK cells. The responding T cells included iNKT cells, MAIT cells, and V?2+ ?? T cells. These results delineate a novel integrin-mediated pathway of IFN-? secretion that is a shared feature of innate lymphocytes.

SUBMITTER: Sharma A 

PROVIDER: S-EPMC6179935 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature