To establish whether Treg cells from patients with asthma are functionally competent, we investigated the expressions of Neuropilin-1 (Nrp-1), cytotoxic T lymphocyte-associated antigen-4 (CTLA-4), and glucocorticoid-induced tumor necrosis factor receptor (GITR), which are related to the suppressive function of Treg cells. Here, CTLA4 is linked to asthma.