Abstract
In this study, we analyzed aging-related changes in the mucosal immune responses of the upper airway to outer membrane protein (OMP) from nontypeable Haemophilus influenzae, focusing on the differentiation of T cells. Mice of different ages (5 weeks, 6 months, and 1 year old) were vaccinated with 10 μg of OMP and 1 μg of cholera toxin for a total of three times seven days apart. On day 7 after immunization, mononuclear cells were collected from the middle ear, nasal mucosa, nasal-associated lymphoid tissue, cervical lymph node, and spleen to analyze T cell differentiation using flow cytometry. Non-immunized mice at each age group served as the controls. An analysis of the lymphocyte region of mononuclear cells using flow cytometry showed that CD3-positive T cells tended to decrease in lymphoid tissues due to aging. In contrast, among CD4-positive T cells, the memory T cell ratio was increased in the upper airway mucosa of young mice after immunization. Similarly, the effector T cell ratio was increased markedly in the lymphoid tissues of young mice after immunization. Therefore, it was suggested that the T cell immune responses against OMPs in the upper airway mucosa and lymphoid tissues may decrease due to aging.
