To investigate ageing‐associated changes in cellular immunity, we recruited three groups of healthy subjects based on SENIEUR protocol criteria. In addition, 10 subjects were randomly selected from each group to isolate their T cells from peripheral blood mononuclear cells; T cell proliferation after phytohemagglutinin (PHA) stimulation was determined by methyl thiazolyl tetrazolium assays. There were no marked differences in the absolute numbers of peripheral blood T cells, NK cells or B cells among the three groups (P > 0.05). Also, no significant differences were noted in the numbers of CD4+ cells, CD8+ cells, or the CD4+/CD8+ ratios (P > 0.05). After PHA stimulation, T cell proliferation was markedly increased, with the highest level in group C and the lowest level in group A (P < 0.05). Cytokine‐induced killer tumouricidal activities were also dramatically increased, with the highest activity in group C and the lowest activity in group A (P < 0.05). Our findings suggest that the number of immune cells remains unchanged with advanced age. However, there is a trend for decreased cellular immunity with an increase in age.
The nasal-associated lymphoid tissues (NALTs), embedded in the submucosa of murine upper respiratory tract, represents an important site of induction for local mucosal immune responses to airborne pathogens and intranasal vaccines. Here, we systematically investigated the mucosal humoral and cellular immune responses of NALTs in mice infected with A/Beijing/501/2009 (BJ501) and A/Puerto Rico/8/1934 (PR8) viruses. Compared with PR8 infection, BJ501 induced a more rapid increase of virus-specific IgA and IgG antibodies in the nasal lavage fluid and a higher ratio of IgG1/IgG2a, indicating a stronger Th2 response to BJ501 in mucosal immunity. In addition, using virus-specific enzyme-linked immunospot assay (ELISpot assay), we observed higher and earlier responses of virus-specific IgA and IgG antibody-secreting cells (ASCs) and IFN-γ and IL-4 cytokine-secreting cells (CSCs) in NALTs of mice intranasally infected with BJ501 virus. In particular, the frequency of BJ501-specific IFN-γ-CSCs significantly correlated with the kinetics of BJ501 virus load in NALTs, suggesting an important role of IFN-γ-CSCs-associated mucosal cellular immune responses in BJ501 virus clearance. Collectively, BJ501 induced a more comprehensive and rapid mucosal immune responses in NALTs of mice, providing further understanding of the immune responses elicited by 2009 pandemic H1N1 virus in upper respiratory tract.
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