In this study, we examined the antigen specific immunoglobulin (Ig) contents in nasopharyngeal lavage fluid and antigen specific Ig production by NALT lymphocytes in rats immunized by various routes. OA specific IgG SFC in NALT lymphocytes was higher than that in spleen lymphocytes in locally immunized rats, whereas the inverse relationship was noted in generally immunized rats. These OA-specific IgG SFC were remarkably increased in NALT, but not so increased in spleen following nasal booster challenge. However, the number of OA specific IgA SFC in freshly obtained lymphocytes was very low in both NALT and spleen even after topical antigen challenge. A significant increase of antigen-specific IgA and IgG levels was noted in the naso-pharyngeal lavage fluid of immunized animals, whereas these Ab levels were not changed 48 h after topical antigen challenge. OA specific IgA SFC were revealed to be increased after in vitro stimulation with lipopolysaccaride (LPS). A preliminary study showed that further increase of antigen-specific IgA as well as IgG production by NALT lymphocytes occurred in the presence of TGF-beta and IL-5.