Phenotype of peripheral blood (PB) and synovial fluid (SF) T cells from patients with juvenile idiopathic arthritis. (a) Expression of activation markers. (b) Expression of differentiation markers. Bars represent median expression on paired PB and SF samples. Because of variation in cell numbers isolated from each sample, not all samples could be stained for every antibody available. Each datum point represents an individual sample (n = number of samples studied). MFI = median fluorescence intensity.