CTLA4 and systemic lupus erythematosus: It is important to note that CD4+ CTLA4+ co-expression in lymphocytes did not solely indicate Tregs, as all mononuclear cells express CD4 protein [51], and monocytes, macrophages, and dendritic cells also express CTLA-4 protein [37], which suggested that these cells play a role in the pathogenesis of SLE and influence the severity of the disease.