miR-21 regulates aberrant T cell responses through control of PDCD4 expression in human systemic lupus erythematosus [36], suggesting that miR-21 induction enables T cells to elude apoptosis and enhance the secretion of pro-inflammatory cytokines such as interferon-γ and interleukin-17 by repressing PDCD4 expression [37]. Here, PDCD4 is linked to systemic lupus erythematosus.