To downregulate the expression of miR-21 in lupus CD4+ T cells and evaluate the effect on Tfh cell differentiation, we isolated CD4+ T cells from peripheral blood of patients with SLE and transfected them with Antagomir-21 and then stimulated them with anti-CD3/CD28 antibodies for two days. The gene discussed is CD28; the disease is systemic lupus erythematosus.