Figure 3 Frequencies of memory B cells expressing recombination‐activating genes 1 and 2 (RAG1 and RAG2) mRNA isolated from children with oligoarticular juvenile idiopathic arthritis (o‐JIA). Individual peripheral B cells isolated from three children with o‐JIA and three age‐matched healthy children bearing the indicated phenotype (CD19+ CD27+ CD5+ or CD19+ CD27+ CD5−) were sorted by fluorescence‐activated cell sorter. Only β‐actin‐positive (n) B cells were analysed. The frequency of cells expressing RAG1 mRNA in the total cohort was determined by single‐cell polymerase chain reaction and is indicated on the y axis. The bars indicate the range among individual patients.