Unsupervised clustering of LPS-stimulated CD14+ MPs exposed to distinct cytokine treatments. CD14+ MPs were stimulated in parallel with LPS and exposed after 1 h to 42 individual cytokines (see Table 1 for cytokines used). Antisense RNA obtained 4 and 9 h following LPS stimulation was hybridized to custom-made 17K cDNA arrays. Unsupervised Eisen clustering  was applied to the complete, unfiltered dataset of 98 experiments. Arrowheads represent control samples that did not receive any stimulation and were obtained at different time points to parallel culture conditions during stimulation (0, 4 and 9 h). Light blue and gold represent samples obtained 4 and 9 h after stimulation, respectively and black represents no stimulation. A375 is a melanoma cell line that was used for quality control alternating conventional (Cy5, red) or reciprocal (Cy3, green) labeling every 25 experiments as previously described . Experiments cluster closer together according to time rather than type of stimulation, with samples obtained after 4 h clustering together (4') with the exception of few cytokines (4"). With few exceptions (9"), cytokine treatments at 9 h clustered together with non-stimulated MPs (9').