CD4 and rheumatoid arthritis: Acthar® Gel (repository corticotropin injection) is a complex mixture of adrenocorticotropic hormone (ACTH) analogs and other pituitary peptides that is approved by the US Food and Drug Administration (FDA) to treat several inflammatory and autoimmune diseases involving activated CD4+ and CD8+ cells, including RA, MS, and sarcoidosis (Mallinckrodt Pharmaceuticals, 2021).