IL21 and systemic lupus erythematosus: IL-21 implication in human SLE remains to be moreextensively investigated since in several murine models of SLE, IL-21 has been eitherdirectly or indirectly shown to be a contributing factor to disease (51,53).Recently, Dolff et al. (80) published the firststudy demonstrating increased proportions of circulating IL-21+ T-cells in SLE patients.Elevated plasma IL-21 in SLE is probably a result of Tfh cell activity in the formationof germinal centers (17).