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

Abstract

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. Objectives The 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 methods We 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 ( τ T) levels in CSF were also measured. Results Patients 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 τ T levels ( Rs = 0.46, p = 0.048). Conclusions Our 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.