Heatmap display of antibody expression pattern. (A) Hiearchical cluster analysis of all 768 screened antibodies ordered by Euclidean distance measure (unweighted pair-group average with arithmetic mean) for plasma (PL) from all 10 patients, revealing distinguishing expression patterns. The degree of antibody binding is reflected in the color intensity of the heatmap, whereby the more intense the red, the more antibody is bound to a given antigen. Clustering and seriation of both antibody target ID's in rows and individual patient samples in columns segregates the study cohort by antibody expression levels. Two core patient clusters are revealed: lower antibody levels (Patients O1, O3, E1, E2, E3 and P3); and higher antibody levels (Patients O2, P1, P2 and P4) (red in patient sample dendrogram). (B) Levels of the conventional laboratory measures C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are plotted for the study cohort with patients split into two groups defined above in (A) by low or high antibody levels. Error bars represent standard deviation; no significant difference exists between the two groups. (C) Hierarchical cluster analysis of autoantibody levels detected with differences of at least 45% between synovial fluid (SF) and PL. The majority of these antibodies are elevated in plasma relative to synovial fluid.