Figure 6.

UVB does not alter IKKβ phosphorylation via delay of IL-1 receptor internalization. (A) Cells were left untreated or stimulated with IL-1 (10 ng/ml) alone or in combination with UVB (300 J/m²) for the indicated time points. Subsequently, IL-1 receptor expression was analyzed by flow cytometry using an IL-1 receptor specific antibody compared to an isotype control of the secondary antibody (FITC). The mean fluorescence intensity (MnX) of three independently performed experiments of this control was set as 1. Receptor expression levels were determined respectively and the MnX of three independently performed experiments compared to FITC control is presented. Consequently, an MnX of 1 in the experiments represents a completely internalized or degraded receptor. (B) The hypothesis of receptor internalization leads to a considerably inferior fit quality (χ² = 24.77 + 25.35 = 50.12). The model largely diverges from the experimental data for the 30 min value following IL-1 stimulation and systematically underestimates the last 5 data points following IL-1 + UVB stimulation.