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BackgroundGender-related differences in humans are commonly observed in behaviour, physical activity, disease, and lifespan. However, the notion that age-related changes in the immune system differ between men and women remains controversial. To elucidate the relationship between immunological changes and lifespan, peripheral blood mononuclear cells from healthy Japanese subjects (age range: 20–90 years; N = 356) were analysed by using three-colour flow cytometry. The proliferative activities and cytokine-producing capacities of T cells in response to anti-CD3 monoclonal antibody stimulation were also assessed.ResultsAn age-related decline in the number of T cells, certain subpopulations of T cells (including CD8+ T cells, CD4+CDRA+ T cells, and CD8+CD28+ T cells), and B cells, and in the proliferative capacity of T cells was noted. The rate of decline in these immunological parameters, except for the number of CD8+ T cells, was greater in men than in women (p < 0.05). We observed an age-related increase or increasing trend in the number of CD4+ T cells, CD4+CDRO+ T cells, and natural killer (CD56+CD16+) cells, as well as in the CD4+ T cell/CD8+ T cell ratio. The rate of increase of these immunological parameters was greater in women than in men (p < 0.05). T cell proliferation index (TCPI) was calculated from the T cell proliferative activity and the number of T cells; it showed an age-related decline that was greater in men than in women (p < 0.05). T cell immune score, which was calculated using 5 T cell parameters, also showed an age-related decline that was greater in men than in women (p < 0.05). Moreover, a trend of age-related decreases was observed in IFNγ, IL-2, IL-6, and IL-10 production, when lymphocytes were cultured with anti-CD3 monoclonal antibody stimulation. The rate of decline in IL-6 and IL-10 production was greater in men than in women (p < 0.05).ConclusionAge-related changes in various immunological parameters differ between men and women. Our findings indicate that the slower rate of decline in these immunological parameters in women than that in men is consistent with the fact that women live longer than do men.

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To examine functions of two small heat shock proteins of Escherichia coli, IbpA and IbpB, we constructed His–IbpA and His–IbpB, in which a polyhistidine tag was fused to the N‐terminals. Both purified His–IbpA and His–IbpB formed multimers, which have molecular masses of about 2.0–3.0 MDa and consist of about 100–150 subunits. They suppressed the inactivation of several enzymes including citrate synthase and 6‐phosphogluconate dehydrogenase by heat, potassium superoxide, hydrogen peroxide and freeze‐thawing, but not the inactivation of glyceraldehyde‐3‐phosphate dehydrogenase by hydrogen peroxide. Both His–IbpA and His–IbpB suppressed enzyme inactivation by various treatments and were also found to be associated with their non‐native forms. However, both His–IbpA and His–IbpB were not able to reactivate enzymes inactivated by heat, oxidants or guanidine hydrochloride. When heated to 50 °C, each multimeric form of His–IbpA or His–IbpB was dissociated to form a monomer for His–IbpA, and an oligomer of about one‐quarter size for His–IbpB. These structural changes were reversible, as both heated proteins regained the multimeric structures after incubation at 25 °C. However, when exposed to hydrogen peroxide or potassium superoxide, the large multimeric forms of His–IbpA and His–IbpB were maintained. The results suggest that His–IbpA and His–IbpB suppress the inactivation of enzymes and bind non‐native proteins to protect their structures from heat and oxidants.