Cluster analysis of cytokines concentration in SF from RA patients. Hierarchical Cluster analysis of cytokines expression profiles obtained for 30 RA patients (Spearman rank correlation and single linkage algorithm). Dendrogram resulting from clustering the RA SFs (rows) identified four principal groups of patients (C1-C4). The most intense red blocks represent highly over-expressed cytokines and most intense green blocks represent the cytokines with greatest degree of under-expression. Black indicates cytokines whose expression is similar in the AR and OA reference samples. At the right side C3A and C3B denote two subclusters of cluster 3 showing different levels of IL-15Ralpha expression. RF+ indicates patients which are positive to Rheumatoid factor.