Effects of a single intranasal (i.n.), subcutaneous (s.c.) or intravenous (i.v.) vaccination and their combined vaccination of priming and boosting on a primary and a secondary IgA antibody forming cell (AFC) response were examined in the nasal associated lymphoid tissue (NALT), spleen and popliteal lymph nodes (pLNs) of BALB/c mice. Mice were primed with the vaccine prepared from A/Yamagata/120/86 (H1N1) together with a cholera toxin-adjuvant and boosted with the same vaccine 3 weeks later Three days after boosting, IgA-AFC responses in each lymphoid tissue were measured as an index of the immunological memory that mediates a secondary IgA-AFC response. Single i.n. vaccination induced a greater primary IgA-AFC response in the NALT not only than that in the spleen or pLNs, but also than that induced by single iv or sc. vaccination. The combination of in, priming and in. boosting afforded a greater anamnestic IgA-AFC response in the NALT not only than that in the spleen or pLNs, but also than that induced by any other combinations of priming and boosting (in.-i.v, i.n.-s.c., s.c.-i.n., s.c.-i.v., and s.c.-s.c.). These results showed that in. priming induced a greater primary IgA-AFC response in the NALT and simultaneously induced the immunological memory that mediated a greater secondary-type AFC response following i.n. boosting in the NALI: (C) 1998 Elsevier Science Ltd. All rights resented.