It has been proposed that CD28 absence in T lymphocytes is associated with two biological events: cell senescence31, 32 and extended exposure to antigens.33 However, there are controversial studies showing that there is no correlation between aging and the expression levels of CD8 + CD28 − T‐cell population.34 In this respect, we do not find a significant correlation between the CD3 + CD8 + T cells positive for CD28 and the age of RA patients (data not shown). Here, CD28 is linked to rheumatoid arthritis.