TFH cells, a subset of T helper cells, specialize in helping B cells to become professional antibody producers.46 An increasing amount of evidence indicates the pathogenic role of TFH cells in human lupus; this evidence includes alterations in the phenotype of circulating TFH cells and increases in their population size.47–49 BCL-6, CD40L, ICOS, and IL-21 have been acknowledged as master regulators for the development and function of TFH cells. Here, IL21 is linked to systemic lupus erythematosus.