To determine the effect of the downregulation of BCL-6 expression on SLE CD4+ T cell function, BCL-6 expression was knocked down in SLE CD4+ T cells, and the mRNA and protein expression levels of CD40L, ICOS, and IL-21 in SLE CD4+ T cells were then detected. The gene discussed is BCL6; the disease is systemic lupus erythematosus.