Interleukin-12 is reduced in cerebrospinal fluid of patients with Alzheimer's disease and frontotemporal dementia

Interleukin-12 is a heterodimeric cytokine produced by activated blood monocytes, macrophages and glial cells. It enhances differentiation and proliferation of T cells and increases production of proinflammatory cytokines, such as Interferon-γ and Tumor Necrosis Factor-alpha. There is little information about the involvement of IL-12 in the pathophysiology of Alzheimer's disease (AD) and other tauopathies.ObjectivesThe objective of our study was to assess the role of IL-12 as a potential marker of immune reactions in patients with AD and frontotemporal dementia (FTD).Patients and methodsWe measured by immunoassay cerebrospinal fluid (CSF) IL-12 levels in 19 patients with AD and 7 patients with FTD in comparison with CSF IL-12 levels in 30 patients with non-inflammatory neurological diseases served as neurological control patients (NCTRL). IL-12 levels were correlated with age, age of disease onset, disease duration, MMSE score, and rate of dementia progression. Aβ42 and Total tau (τT) levels in CSF were also measured.ResultsPatients with AD had significantly lower CSF IL-12 levels compared with NCTRL patients (p < 0.001). Patients with FTD had also lower CSF IL-12 levels compared with NCTRL patients (p < 0.05). Age, sex, disease duration and MMSE score did not affect IL-12 levels in any of the groups. In AD a significant positive correlation was noted between IL-12 levels and τT levels (Rs = 0.46, p = 0.048).ConclusionsOur findings may suggest a reduced inflammatory reaction during the course of AD and FTD. A neurotrophic role of IL-12 and other proinflammatory cytokines cannot be excluded.