PFKFB3 and rheumatoid arthritis: Furthermore, in RA, studies have shown increased NADPH oxidase/Nox2 in circulating leukocytes and synovium26, altered expression of 6-phosphofructo-2-kinase/fructose-2, 6-bisphosphatase 3 (PFKFB3) in naive CD4 T cells27, and synovial deficiency of cytochrome C oxidase which is the most commonly recognised respiratory chain defect24.