Using senescence-accelerated mouse (SAM) strains and aged C57/BL/6 mice, we examined the senescence-related changes of mucosal immune responses.

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The obtained findings are as follows:1. Mitogenic responses of the splenic B cells from senescence-prone (SAM-P) mice were significantly lower than those of senescence-resistant (SAM-R) mice, although the kinetics was not altered2. The polyclonal B cell activation induced by Porp/iyromonas gingivalis LPS in SAM-P mice was also diminished. However, the alteration in SAM-P mice occurred rehitively earlier than the reduction of mitogenic responses in SAM-P mice.3. Analysis of ovalbumin (OVA)-specific antibody-forming B cell responses in aged (12-month-old and 24-month-old) mice immunized orally with OVA and mucosal adjuvant (cholera toxin) revealed the significant reductions in mucosal immune responses (antigen-specific IgA antibody-forming B cell responses) in Peyer's patches and in lamina propria, as well as systemic immune responses in spleen.4. However, development of the senescence-related alterations could occur earlier in mucosal immune system than in the systemic immune compartment.5. Flow cytometric analysis of T cell phenotypes indicated that the percentage of the T cell subset with extrathymic properties in SAM-P mice was significantly higher than that in SAM-R mice.Taken together, these findings indicated that both the reduction of B cell responses and the alteration in T cell subsets could occur in aged mice, which may reflect a senescence-related down-regulation in mucosal immune responses in aged mice.