Figure 6

Psoriasis lesions from 163 patients can be divided into two subgroups based upon inflammatory gene expression patterns (strong inflammation: 91/163; weak inflammation: 72/163). For each cell population, we identified 250 “signature genes” most specifically expressed in that cell population relative to all other cell types. For each patient, a signature score was calculated as the weighted average of fold-changes (PP/PN) among these 250 signature genes (weighted arithmetic mean). Weighted averages were calculated by assigning greatest weight to the top-ranked gene most specifically expressed in a given cell type, with weights declining between the top-ranked and 250th-ranked gene. Values in the bottom margin indicate the proportion of patients with significantly large (red) or small (blue) signature scores (P < 0.05). Significance was evaluated by comparing fold-changes (PP/PN) of the 250 signature genes to those of all other genes represented on the array (Wilcoxon rank sum test). Patients were clustered according to signature scores using complete linkage and the Euclidean distance metric. Group assignments were made based upon whether a patient’s scores approximated a strong or weak pattern of inflammation (see legend).