CD4 and systemic lupus erythematosus: Indeed, the de novo appearance of PsA in patients with acquired immunodeficiency syndrome and advanced depletion of CD4+ T cells during the early stages of the human immunodeficiency virus pandemic suggested different roles of T cells in PsA than those in RA and systemic lupus erythematosus (SLE), which are both ameliorated by a loss of CD4+ T cells [24].