NASAL-ASSOCIATED LYMPHOID-TISSUE IS AN INDUCTIVE SITE FOR RAT TEAR IGA ANTIBODY-RESPONSES

The role of nasal-associated lymphoid tissue (NALT) as a mucosal induc tive site for tear IgA antibody responses was investigated in the rat model. Fluorescent microspheres were shown to access and be taken up b y NALT after intranasal or ocular-topical administration, although few er microspheres were found in the latter case. Tear IgA anti DNP antib ody responses to dinitrophenylated Streptococcus pneumoniae were 6 mu g/ml at day 7, 10 mu g/ml at day 10, and were still detectable on day 21 (5 mu g/ml) following ocular or gastrointestinal immunization. Intr anasal immunization induced tear IgA responses which were 1.7-fold hig her at day 7 (10 mu g/ml), peaked by day 10 (14 mu g/ml) and were stil l 1.6-fold higher (8 mu g/ml) at day 21 than responses of ocular or ga strointestinal groups. These findings suggest that intranasal immuniza tion may be more effective than ocular or gastrointestinal administrat ion in eliciting tear IgA antibody responses and, taken together with the microsphere data, indicate that NALT can serve as Bn inductive sit e for ocular mucosal IgA responses.