It is remarkable that, in rheumatoid arthritis (RA), a recent study showed that in contrast to healthy T cells, RA CD4 T cells fail to produce as much ATP and lactate due to the insufficient induction of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), a rate-limiting enzyme in the glycolytic pathway.15 Deficient activity of PFKFB3 shunts glucose towards the pentose phosphate pathway and generates increased levels of nicotinamide adenine dinucleotide phosphate (NADPH), which in turn eventually reduces intracellular reactive oxygen species (ROS). The gene discussed is CD4; the disease is rheumatoid arthritis.