Activation of human eosinophils through leukocyte immunoglobulin-like receptor 7 - PubMed (original) (raw)

Activation of human eosinophils through leukocyte immunoglobulin-like receptor 7

Nicodemus Tedla et al. Proc Natl Acad Sci U S A. 2003.

Abstract

Eosinophils are implicated prominently in allergic diseases and the host response to parasitic infections. Eosinophils may be activated in vitro by diverse classes of agonists such as immunoglobulins, lipid mediators, and cytokines. The leukocyte Ig-like receptors (LIRs) comprise a family of inhibitory and activating cell-surface receptors. Inhibitory LIRs down-regulate cellular responses through cytoplasmic immunoreceptor tyrosine-based inhibitory motifs. There are limited data on the action of the activating LIRs, which are thought to signal through the Fc receptor gamma chain, which contains an immunoreceptor tyrosine-based activation motif. We now demonstrate the expression of LIR1 (inhibitory), LIR2 (inhibitory), LIR3 (inhibitory), and LIR7 (activating) on eosinophils from 4, 4, 12, and 11, respectively, of 12 healthy donors. Cross-linking of LIR7 with plate-bound antibody elicited the dose- and time-dependent release of eosinophil-derived neurotoxin and leukotriene C(4). Eosinophils activated with antibodies to LIR7 embedded in gel-phase EliCell preparations showed leukotriene C(4) generation at the nuclear envelope and the release of IL-12 but not IL-4 by vesicular transport. Thus, LIR7 is an activating receptor for eosinophils that elicited the release of cytotoxic granule proteins, de novo lipid mediator generation, and cytokine release through vesicular transport.

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Figures

Figure 1

Figure 1

Flow-cytometric analysis of LIR expression. Cell-surface expression of LIRs on eosinophils, neutrophils (polymorphonuclear leukocytes, PMN), and monocytes was analyzed as described in Materials and Methods. mAbs directed to CD9, CD16, and CD14 were used as markers for eosinophils, polymorphonuclear leukocytes, and monocytes, respectively. Representative histograms are shown.

Figure 2

Figure 2

Time course of release of EDN. Purified eosinophils were stimulated with plate-bound mAb (5 μg/ml) to LIR7 (filled circles), to CD9 (open circles), or to MHC class I (filled triangles) as described in Materials and Methods (n = 3). Results are means ± SE.

Figure 3

Figure 3

LTC4 generation by eosinophils. Agarose-embedded eosinophils were stimulated with recombinant eotaxin (12 nM), with A23187 (0.1 μM), with mAbs to CD9 (2.5 μg/ml), LIR7 (10 μg/ml), or MHC class I (10 μg/ml), or with irrelevant mouse IgG1 control (10 μg/ml) for 1 h. Cells were fixed and stained with Alexa 488-labeled anti-cysteinyl LT mAb. The data are expressed as the percentages of cells containing immunodetectable LTC4. *, P < 0.05 compared with medium alone or control IgG1 (n = 3).

Figure 4

Figure 4

Intracellular localization of LTC4 biosynthesis. Agarose-embedded eosinophils were stimulated with 12 nM eotaxin (A), 2.5 μg/ml mAb to CD9 (B), or 10 μg/ml mAb to LIR7 (C) for 1 h. Cells then were fixed and stained with Alexa 488-labeled anti-cysteinyl LT mAb. To facilitate intracellular localization, anti-LTC4 immunoreactive sites (green staining) were overlaid on phase-contrast images. (Bar, 5 μm.) The figure is illustrative of three independent experiments.

Figure 5

Figure 5

IL-12 and IL-4 release by eosinophils. Agarose-embedded eosinophils were stimulated with eotaxin (6 nM), A23187 (0.5 μM), mAb to CD9 (2.5 μg/ml), mAb to LIR7 (10 μg/ml), mAb to MHC class I (10 μg/ml), or mouse IgG1 control (10 μg/ml). IL-12 and IL-4 release was determined by using the EliCell assay. The data are reported as the percentage of cells with detectable cytokine release. Shown is release of IL-12 (A) and IL-4 (B) in response to each stimulus at 1 h. The data are expressed as percentage of cells releasing each cytokine. *, P < 0.05 compared with medium alone or control IgG1 (n = 3–5).

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