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Figure 4 | Arthritis Research & Therapy

Figure 4

From: Interleukin-15 and interferon-γ participate in the cross-talk between natural killer and monocytic cells required for tumour necrosis factor production

Figure 4

Reciprocal activation between NK and THP-1 cells, the role of IL-15 and IFN-γ. (a) IL-15 and β2 integrins are involved in the intercellular contact with THP-1 cells that induces the expression of CD69 in natural killer (NK) cells. Peripheral blood lymphocytes (PBL) were co-cultured with THP-1 cells (10:1 ratio of PBL to THP-1) for 24 hours in medium alone or in the presence of an anti-β2 integrin mAb (Lia3/2) or an anti-IL-15 mAb (MAB647). As a control, both cell lines were separated by a 0.4 μm pore transwell. A representative experiment of the five performed is shown. The histograms represent the CD69 expression in CD56+ cells in the medium (grey histogram in all panels) or under the different conditions (solid black line in each panel); a negative control is also shown (dotted histogram in all panels). (b) Intercellular contact between THP-1 and NK cells induces IFN-γ production. NK cells were cultured in the presence of 50 ng/ml IL-15 for 24 hours, or in medium alone, and the NK cells were then washed and incubated together with THP-1 cells. In some conditions the cells were separated by a 0.4 μm pore transwell and after 24 hours the supernatants were harvested to measure the IFN-γ content with the use of an enzyme immunoassay. The data show the IFN-γ concentrations and are expressed as means ± SEM from six independent experiments. One-way analysis-of-variance model with Bonferroni multiple-comparison correction was used to determine statistical significance. (c) IFN-γ increases IL-15 membrane expression in THP-1 cells. Cells were incubated with IFN-γ (100 ng/ml), TNF (100 ng/ml) or IL-1 (100 ng/ml) for 24 hours and then the membrane-bound IL-15 (mIL-15) was measured by indirect immunofluorescence and flow cytometry. A representative experiment of the five performed is shown. Grey histograms represent mIL-15 on stimulated THP-1 cells, solid-line histograms represent basal mIL-15 expression, and the dotted-line histogram is the negative control.

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