Abstract
Background: Peripheral inflammation has been suggested to influence the
development of Alzheimer’s disease (AD). Elevated levels of pro-inflammatory markers in
the plasma of patients with AD indicate that a systemic pro-inflammatory status occurs
concomitantly with inflammatory changes in the brain.
Objective: To investigate whether allergy influences the levels of
immunoglobulins (Ig) and of pro- and anti-inflammatory cytokines in the serum and
cerebrospinal fluid (CSF) from patients with AD, mild cognitive impairment (MCI), and
subjective cognitive impairment (SCI).
Methods: IgA, IgG, and its subclasses, IgM, and cytokines were analyzed in
CSF and serum from patients with SCI, MCI, and AD, with or without allergy. The relation
between allergy and Mini-Mental State Examination (MMSE) scores, and between allergy and
CSF biomarkers for AD (phosphorylated (p)-tau, total (t)-tau, amyloid-β 42
(Aβ42), were analyzed.
Results: In MCI, the CSF levels of IgG2 were lower in allergic patients, and
in AD, the levels of IgA and the IgG1/total IgG ratio were lower in allergic patients,
compared to patients without allergy. MCI subjects with allergy had higher serum IgM
levels compared to those without allergy. CSF levels of Aβ42 were lower and
MMSE scores were higher in AD patients with allergy than in those without allergy.
Conclusions: The presence of allergy was associated with seemingly beneficial
effects on AD as suggested by higher Aβ42 levels in CSF, and higher MMSE
scores. Higher IgM levels and lower other Ig classes suggest that allergy may influence
senescence of the immune response.
