Cytokine levels and phagocytic activity in patients with Alzheimer's disease

Background: Clinical observations indicate that patients with Alzheimer's disease show a greater susceptibility to infections. One possible explanation is that this predisposition is due to alterations in their immune system. Objective: To investigate this assumption, pro- and anti-inflammatory cytokines, as well as the phagocytic activity and superoxide anion generation was examined in aged individuals with and without Alzheimer's disease. Methods: The production of IL-1β, IL-2, IL-6, TNFα and IL-10 by peripheral blood mononuclear cells from 12 patients with Alzheimer's disease was compared with that of 12 age-matched individuals without any signs of dementia and 12 middle-aged healthy volunteers who served as an additional control. The engulfing capacity of the phagocytic cells was detected by counting cells containing latex beads and the number of particles internalized by each individual cell. Results: The secretion of IL-2 was markedly low in the demented patients, compared with both elderly and middle-aged subjects. IL-1β and TNF production was similar in the individuals of the 3 groups. The production of IL-6 and IL-10 was significantly lower when compared to that of the middle-aged, but did not differ between the elderly patients with and without dementia. The phagocytic function of both polymorphonuclear cells and monocytes was decreased in individuals of the elderly groups with a low number of engulfed latex particles by each individual polymorphonuclear cell. The production of superoxide anions was increased only by monocytes from the elderly groups. Conclusions: The results suggest that although the impaired immune function in patients with Alzheimer's disease is related to the aging process, the significant low IL-2 production in these patients may play a role in their increased susceptibility to infections.