To develop a mucosal vaccine strategy for the elderly, we have compared mucosal and systemic immune responses between aged (12-14 months) and young adult (8-12 weeks) mice. Both aged and young mice were immunized weekly with three oral doses of 1 mg of ovalbumin (OVA) and 10 μg of cholera toxin as adjuvant. Although elevated levels of OVA-specific systemic IgG and mucosal IgA Ab responses were seen in young mice, aged mice showed impaired antigen- specific mucosal and systemic immune responses. These results suggest that mucosal immunity is down regulated in aged mice. (C) 2000 Elsevier Science Ltd.