Comparison of murine nasal-associated lymphoid tissue and Peyer's patches

The nasal mucosal is the first site of contact with inhaled antigens. However, the nature of local immune responses and the role of nasal-associated lymphoid tissue (NALT) in those responses have rarely been studied. To characterize the cells involved in mucosally derived immune responses, NALT and Peyer's patch (PP) cells from normal mice, and mice immunized intragastrically or intranasally with cholera toxin (CT), were isolated and analyzed. Compared with PP cells, unstimulated NALT cells contained a higher proportion of T-cells. The CD4:CD8 ratio in NALT cell preparations was less than that observed in PP and more closely resembled that seen in spleen. Additionally, the total B-cell frequency in NALT cell isolates was 20% lower than that observed in PP cell preparations. Although NALT and PP cell isolates contained both mature B-cells and cells undergoing activation to express surface IgA, unlike PP, NALT showed no significant frequency of IgA-switched cells. After intranasal immunization with CT, toxin-specific IgA antibody-forming cells (AFCs) were detected in NALT cell preparations. The numbers of these cells correlated with CT-specific IgA in nasal, but not in gut washes or sera, thus suggesting local nasal production of antigen-specific mucosal antibodies. There was no evidence of anti-CT AFCs in NALT or CT-specific antibody in nasal washes after intragastric CT administration. These results support the notion that nasal mucosal antibody production is best achieved via direct stimulation of IgA-committed, NALT-derived B-cells.