Decline of immune responsiveness: a pathogenetic factor in Alzheimer's disease?

The involvement of immunological alterations in the pathogenesis of Alzheimer's disease (AD) is widely discussed. Hitherto, findings on systemic immunological alterations are inconsistent. We measured the concentrations of the pro-inflammatory cytokines IL-1beta, IL-2, IL-6, and TNF-alpha, and of the soluble receptors sIL-2r, sIL-6r, and sTNF-alphar, in cerebrospinal fluid (CSF) and serum of 20 Alzheimer patients and 21 controls. Moreover, we studied levels of the pro-inflammatory IL-6, Il-12, IFN-gamma, and TNF-alpha, and of the anti-inflammatory IL-5 and IL-13 in stimulated blood cell cultures from 27 AD patients and 25 controls. The levels in CSF and serum were diminished in AD or under detection limit. In mitogen-stimulated blood cultures we found a significant decrease of pro- and anti-inflammatory cytokines in the AD group. Our data suggest a general decline of immune responsiveness in AD. Based on the recent research, an impaired immune response may be considered as a pathogenetically relevant factor in AD. With respect to the putative role of ageing in AD, we assume a premature immunosenescence contributing to the Alzheimer's pathology.