PIK3CD and B-cell chronic lymphocytic leukemia: Adoro et al. reported that miR-29 is required for IL-21-induced anti-viral effects in CD4+ T cells [33]; Rasmussen et al. found that miR-155a is required for IL-21-mediated STAT3 phosphorylation in CD4+ T cells from systemic lupus erythematosus (SLE) patients [34]; using microarray analysis, De Cecco et al. found IL-21 regulates CCL17, CD40, DDR1, and PIK3CD expression through miR-663b in chronic lymphocytic leukemia [35].