CD8A and type 2 diabetes mellitus: These metabolic changes may be responsible for the observed impairment of lymphocyte function in T2DM.32 A study reported that patients with T2DM showed increased circulating levels of insulin (insulin resistance) and decreased percentages of total lymphocytes, CD8+ T, effector CD4+ T, and B lymphocytes, while Treg cells were reported to be increased in T2DM.33