Figure 5

NK cell surface molecules involved in the cell-cell interaction that promotes TNF production by monocytes. (a) The effect of IL-15 on the expression of cell surface molecules by natural killer (NK) cells. NK cells were cultured with IL-15 at 50 ng/ml or medium alone for 24 hours, and the expression of different surface molecules was then assessed by flow cytometry. Grey-filled histograms represent the expression of each molecule on resting NK cells, the grey-line histograms represent the expression on IL-15 activated NK cells, and the dotted-line histograms represent the negative control. One representative experiment is shown. (b) Effect of different antibodies against NK cell surface molecules on TNF production in co-cultures of NK and THP-1 cells. IL-15-stimulated NK cells were co-cultured with THP-1 cells at a 10:1 cell ratio for 24 hours in the presence of different monoclonal antibodies (see the Materials and methods section for further information). The TNF concentration in cell-free supernatants was quantified with an enzyme immunoassay. The results show the percentage TNF production and are expressed as means ± SEM for eight independent experiments (see the Materials and methods section for definition). Staistical significance:*p < 0.01; ^§p < 0.05; analysis-of-variance test. (c) Expression of CD244 and CD48 on monocytes and THP-1 cells. The solid-line histogram represents the expression of each molecule and the grey histogram the negative control.