CD19 and juvenile idiopathic arthritis: No significant differences were observed in the frequencies of transitional B cells (CD19+IgD+CD38++), naïve B cells (CD19+IgD+CD27-), pre-switch memory (pre-SM, CD19+IgD+CD27+), post-switch memory (post-SM, CD19+IgD-CD27+) and double negative (DN, CD19+IgD-CD27-) B cells between both groups of paediatric JIA patients (persistent oligo JIA and extended oligo+poly JIA) in comparison to controls (figure 1B).