CD4 and rheumatoid arthritis: Remarkably, in combination with PBMCs from patients diagnosed with RA, APL‐1, an altered peptide ligand originated from human heat‐shock protein 60 with the D19 mutation to L19, stimulates programmed cell death of autoreactive CD4+ CD25+ T cells and enhances IL‐10 production.[123] The potential of APLs to halt disease progression is evaluated using animal studies.