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Immunosurveillance requires the migration of lymphocytes and their activation to induce proliferation and effector function. Effective immunity requires an optimal supply of nutrients to lymphocytes. Cells contain nutrient sensing apparatus such as adenosine 5′-monophosphate-activated protein kinase (AMPK) that surveys intracellular ATP levels. Immunity declines during ageing and one possibility is that the energy balance may be altered in old lymphocytes. This paper summarizes recent data identifying a convergence of senescence and nutrient signalling pathways in lymphocytes that inhibit both T cell and natural killer (NK) cell function during ageing. Significantly, these pathways can be inhibited to enhance the activity of these cells. [ABSTRACT FROM AUTHOR]

Previously, we described a system allowing the study of murine T cell-dependent proliferative responses to Trypanosoma brucei antigens. It was observed that T. brucei-specific T cells could be demonstrated in the regional lymph nodes of primed mice for only 2 to 3 weeks following priming. The results of the present study indicate that this inability to demonstrate a long-lived memory response is due to an immunosuppressive effect of the resulting T. brucei infection. The exact mechanism of the suppression is not known, and appears to function in the absence of demonstrable suppressor cells. Since the T cell responses are strictly dependent on the presence of macrophages, we have investigated whether the loss in responsiveness is due to a defect in the T cell population, or to a loss of macrophage function. Our results show that T cells taken from mice 3 weeks after priming with T. brucei are unable to mount a proliferative response in the presence of a normal macrophage population, and conversely that macrophages taken 3 weeks after infection with T. brucei are unable to elicit a normal proliferative response using a competent primed T cell population. Thus these results indicate that both populations are affected by the parasite infection. [ABSTRACT FROM AUTHOR]