Comitogenic effect of CD26 on CD3-dependent proliferation of CBTCs compared with PBTCs, CD45RA⁺ PBTCs, and CD45RO⁺ PBTCs. (A) Proliferation assays were performed as described in “Materials and methods” with PBTCs and CBTCs incubated in the presence of submitogenic doses of solid-phase immobilized anti-CD3 (OKT-3) and solid-phase immobilized anti-CD26 (1F7) at the doses indicated or anti-CD3 and anti-CD28 (4B10). (B) Proliferation assays data of CBTCs compared with PBTCs expressing CD45RA⁺ or CD45RO⁺. The data are expressed as mean ± standard error for 10 different donors.