Myeloid dendritic cells are decreased in peripheral blood of Alzheimer's disease patients in association with disease progression and severity of depressive symptoms.

BACKGROUND: Dendritic cells (DCs) are major orchestrators of immune responses and inflammation. They are migratory cells, which may play a role in Alzheimer's disease (AD), as suggested by prior in vitro studies. With the intent to investigate the clinical relevance of DC modifications in vivo, the present study was aimed to evaluate the levels of blood DCs in AD patients, in relation to the progression of the disease, the severity of its symptoms, and the treatment with acetylcholinesterase inhibitors (AChEIs), a class of drugs used to improve cognitive functioning in people with dementia. METHODS: The two main subpopulations of immature blood DCs, namely myeloid (mDCs) and plasmacytoid (pDCs) cells, were evaluated by flow cytometry analysis in 106 AD patients, in comparison with the same cells from 65 individuals with mild cognitive impairment (MCI) and 73 healthy control subjects (HC). The relationship between blood DC levels and symptom severity was also assessed in AD patients, and their blood DC frequency was considered both in the absence or presence of treatment with AChEIs. RESULTS: A significant depletion in blood mDCs was observed in AD patients, as compared to HC and MCI subjects. At variance, pDC levels were comparable among the three groups of subjects. The mDC decrease was evident only after the emergence of AD clinical symptoms, as confirmed by the follow-up analysis of a subgroup of MCI subjects who exhibited a significant decline in mDCs after their conversion to AD. Notably, the mDC decline was inversely correlated in AD patients with the frequency and severity of depressive symptoms. Eventually, the mDC depletion was not observable in patients treated with AChEIs. CONCLUSIONS: Our results provide the first evidence that blood mDC levels are dysregulated in AD. This phenomenon appears mainly linked to AD progression, associated with stronger severity of AD-related symptoms, and influenced by AChEI treatment. Taken all together, these data suggest that blood mDCs may serve as a cell source to test disease-induced and treatment-related changes and support the innovative notion that DCs play a role in AD, as ultimate evidence of the immune system participation in disease progression.

Blood dendritic cell frequency declines in idiopathic Parkinson's disease and is associated with motor symptom severity.

The role of inflammation in Parkinson's Disease (PD) is well appreciated, but its underlying mechanisms are still unclear. Our objective was to determine whether dendritic cells (DC), a unique type of migratory immune cells that regulate immunological response and inflammation have an impact on PD. In a case-control study including 80 PD patients and 80 age- and gender-matched healthy control subjects, the two main blood subsets of plasmacytoid and myeloid DC were defined by flow cytometry analysis. Clinical evaluation of subjects consisting of cognition and depression assessment was performed using the Mini Mental State Examination and the Beck Depression Inventory. The severity of motor symptoms was measured using the Unified Parkinson's Disease Rating Scale-Part III. Comparison between patient and control DC measures and their relationships with clinical assessments were evaluated.The following main results were obtained: 1) the level of circulating DC (mainly the myeloid subset) was significantly reduced in PD patients in comparison with healthy controls; 2) after controlling for depressive and cognitive characteristics, the frequency of myeloid DC was confirmed as one of the independent determinants of PD; 3) the number of both myeloid and plasmacytoid DC was negatively associated with motor symptom severity. Overall, the decline of blood DC, perhaps due to the recruitment of immune cells to the site of disease-specific lesions, can be considered a clue of the immune alteration that characterizes PD, suggesting innovative exploitations of DC monitoring as a clinically significant tool for PD treatment. Indeed, this study suggests that reduced peripheral blood DC are a pathologically-relevant factor of PD and also displays the urgency to better understand DC role in PD for unraveling the immune system contribution to disease progression and thus favoring the development of innovative therapies ideally based on immunomodulation.

The stimulation of dendritic cells by amyloid beta 1-42 reduces BDNF production in Alzheimer's disease patients.

Dendritic cells (DCs), the main actors of immune responses and inflammation, may play a role in Alzheimer's disease (AD). Recent studies demonstrate that monocyte-derived DCs (MDDCs), generated in vitro in the presence of amyloid ß1-42 peptide (Aß1-42), show a functional alteration and an increased production of inflammatory molecules. Accordingly, MDDCs from AD patients show a more pronounced pro-inflammatory profile than DCs obtained from control subjects. In this study, we aimed at further investigating DC role in AD. Thus, we analyzed the in vitro effect of Aß1-42 treatment on already differentiated DCs from AD patients, as compared to control subjects. We found that Aß1-42 significantly decreases the expression of brain-derived neurotrophic factor (BDNF) in DCs derived from AD patients but not from control subjects. Thus, possibly due to their Aß-induced reduction of neurotrophic support to neurons, DCs from AD patients might contribute to brain damage by playing a part in Aß-dependent neuronal toxicity.

Increased expression of interleukin-18 receptor in blood cells of subjects with mild cognitive impairment and Alzheimer's disease.

Inflammation has been proposed as a leading force in neurodegeneration and Interleukin (IL)-18 is a pro-inflammatory cytokine which is suggested to be implicated in Alzheimer's disease (AD). However, the meaning of the IL-18 participation in this disease is still unclear. Since IL-18 activity is mediated by its heterodimeric receptor complex IL-18Rα/ß, we evaluated the presence of both IL-18R chains on peripheral blood cells of AD patients, as well as in individuals with Mild Cognitive Impairment (MCI), at increased risk to develop AD. More specifically, we compared the levels of CD14(+) monocytes and CD3(+) T-lymphocytes bearing IL-18Rα and ß chains in the two groups of patients with those in healthy control subjects, both before and after in vitro cell treatment with lipopolysaccharide (LPS). While no differences in the levels of monocytes and T-lymphocytes bearing IL-18Rα chain were found among the three groups, either in untreated and LPS-treated conditions, the IL-18Rß chain expression appeared differently regulated in MCI and AD patients, as compared to controls. In particular, the amount of IL-18Rß-bearing monocytes was similar among the three groups at unstimulated conditions, while after LPS treatment it was increased in MCI vs. controls. A significant increase of IL-18Rß-bearing T-lymphocytes was also observed in MCI and AD vs. controls, both in untreated and LPS-stimulated conditions. Our findings indicate that the expression of IL-18R complex on blood cells is perturbed in AD and even more markedly in its preclinical state of MCI, confirming that an increased peripheral activity of IL-18 may be involved in the early phase of AD pathophysiology.

Effect of age on surface molecules and cytokine expression in human dendritic cells.

Dendritic cells (DCs) are central in regulating both innate and acquired immunity, but their possible age-related functional modifications are still unclear. Here we have analyzed the effect of age on LPS-treated monocyte-derived DCs (MDDCs). A negative correlation between age and cell expression of ICAM-1, CD25 and IL-10 was observed in a group of healthy donors. This has been confirmed by a significantly reduced expression of the same molecules in cells of subgrouped elderly versus younger individuals. On the contrary, a positive correlation between age and cell expression of IL-6 and IL-18 has been reported in all the subjects and further supported by a significant increase of the two pro-inflammatory cytokines in cells of elderly versus young subjects. Our data indicate that aging can impair the expression of ICAM-1 and CD25 and skew the production of cytokines, including IL-18, which concur to make a pro-inflammatory milieu. Altogether, the present results point to additional molecules whose role might be relevant in immunosenescence of human DCs, confirming that these cells undergo functional changes during aging.

Increased pro-inflammatory response by dendritic cells from patients with Alzheimer's disease.

Alzheimer's disease (AD) is characterized by abnormal accumulation of amyloid-beta peptide (Abeta) into extracellular fibrillar deposits, paralleled by chronic neuroinflammatory processes. Although Abeta seems to be causative in AD brain damage, the role of the immune system and its mechanisms still remain to be clarified. We have recently shown that normal monocyte-derived dendritic cells (MDDCs), when differentiated in the presence of Abeta1-42, acquire an inflammatory phenotype and a reduced antigen presenting ability. Here we studied MDDCs derived from AD patients in comparison with MDDCs obtained from healthy control subjects (HC). MDDCs from AD patients, at variance with HC-derived cells, were characterized by an augmented cell recovery, a consistent increase in the expression of the pro-inflammatory ICAM-1 molecule, a decrease in the expression of the co-stimulatory CD40 molecule, and an impaired ability to induce T cell proliferation. Furthermore, MDDCs from AD produced higher amounts of IL-6 than HC-derived cells, confirming the more pronounced pro-inflammatory features of these cells in AD patients. Consistent results have been also obtained with monocytes, the MDDC precursors. In fact, while unstimulated monocytes do not appear to be different in AD and HC, after stimulation with lipopolysaccharide, AD monocytes overexpressed ICAM-1 with respect to controls, suggesting that common pathways of monocyte activation and MDDC differentiation are altered in AD. Overall, these findings show that AD-linked dysregulated immune mechanisms exist, which lead to dendritic cell-mediated over-activation of inflammation and impaired antigen presentation, thus supporting the view that immune cell activation could play an important role in AD pathogenesis.

Detection of human papillomavirus and adenovirus in benign and malignant lesions of the larynx.

OBJECTIVE: To investigate the role of human papillomavirus (HPV) and adenovirus (AdV) infections in the oncogenesis of squamous cell carcinomas of the larynx and of laryngeal dysplasia. STUDY DESIGN: Cross-sectional study with planned data collection. SETTING: Department of Otorhinolaryngology G. Ferreri and Department of Experimental Medicine and Pathology-Section of Virology, Sapienza University of Rome. SUBJECTS AND METHODS: Biopsy samples were taken from 68 patients with benign and malignant lesions of the larynx. All tissue samples were analyzed by means of polymerase chain reaction with two groups of primers for HPV and with a pair of primers for AdV. RESULTS: All cases of carcinomas and dysplasia as well as all control cases were negative for both viruses. Four of the five cases of laryngeal papillomas were positive for only HPV, confirming the role of these viral types in the origin of papillomas. CONCLUSION: The absence of viral genomes in laryngeal carcinomas as in the other cases studied suggests the existence of other factors that play a more important role than viral infection in the carcinogenesis of these lesions.

Disease outcome, alexithymia and depression are differently associated with serum IL-18 levels in acute stroke.

Stroke has been shown to lead to depressive disorders, anxiety disorders and other emotional consequences. Although the cause of these disorders is a subject of debate, stroke has clearly been shown to lead to the production of pro-inflammatory cytokines, which we hypothesized to play a role in the production of post-stroke emotional disorders. Thus we investigated here whether acute stroke might be associated with changes in the normal serum levels of IL-18 and if these changes were related to stroke severity, as well as to the presence and severity of alexithymia and depression. Thirty patients with a first-ever symptomatic ischemic stroke were included. Alexithymia (Toronto Alexithymia Scale; TAS-20), depression (Hamilton Depression Rating Scale; HDRS-17) and serum IL-18 were assessed. Stroke patients showed serum levels of IL-18 significantly related to stroke severity. Furthermore, a strong positive correlation was observed between IL-18 levels and severity of alexithymia, particularly among patients with right-hemisphere lesions. Specifically, circulating concentrations of IL-18 were significantly increased in patients with categorical alexithymia (TAS-20 score 61), as compared with both non alexithymic patients and control subjects. In addition, stroke was more severe in alexithymic patients, as compared to non alexithymic patients. Following multivariate regression, serum IL-18 levels appeared to be specifically associated with alexithymia rather than with stroke severity in patients with right-hemisphere lesions only. These results suggest that IL-18 might be specifically implicated in the pathogenesis of post-stroke alexithymia, ultimately contributing to impaired recovery from stroke.

Amyloid beta peptide promotes differentiation of pro-inflammatory human myeloid dendritic cells.

A key event of Alzheimer's disease (AD) pathogenesis is the production of amyloid beta peptides (A beta), which are hypothesized to lead to neurodegeneration by still unclear mechanisms, including a chronic inflammatory response characterized by innate immune cell activation and pro-inflammatory molecule release. Since dendritic cells (DCs) are central players of innate immune response and brain dendritic-like cells may have a crucial role in AD pathogenesis, this study investigates the effects of A beta on human DC functions. Myeloid DCs differentiated in the presence of A beta 42 showed an increase in survival and soluble antigen uptake, a reduction in HLA molecule expression and in IL-10 and IL-12 production. Accordingly, A beta 42-treated DCs were impaired in inducing T cell proliferation and IL-2 production. On the other hand, A beta 42 treatment provided DCs with the ability to release higher levels of IL-1 beta, IL-6 and IL-18, than control DCs. These results demonstrate that A beta 42 can modulate the immune system by inducing pro-inflammatory DC differentiation, thus gaining new insights into AD pathogenesis and immune-based therapeutic intervention.

Interleukin-18 produced by peripheral blood cells is increased in Alzheimer's disease and correlates with cognitive impairment.

A body of evidence indicates that inflammation plays a pivotal role in AD pathogenesis. IL-18 is a pro-inflammatory cytokine produced in the brain, emerging to be implicated in AD. Although no differences in circulating IL-18 levels were measured between AD patients and controls, a significant increased production of IL-18 was obtained from stimulated blood mononuclear cells of AD patients. This was true particularly in AD subjects carrying the C/C genotype at the -607 position of IL-18 gene promoter. Furthermore, a significant correlation between IL-18 production and cognitive decline was observed in AD patients. Overall, these data indicate that IL-18-related inflammatory pathways, probably also in virtue of polymorphic IL-18 gene influence, are exacerbated in AD patients, and that this cytokine may indeed participate in pathogenic processes leading to dementia.

Isoniazid prophylaxis differently modulates T-cell responses to RD1-epitopes in contacts recently exposed to Mycobacterium tuberculosis: a pilot study.

RATIONALE: Existing data on the effect of treatment of latent tuberculosis infection (LTBI) on T-cell responses to Mycobacterium tuberculosis (MTB)-specific antigens are contradictory. Differences in technical aspects of the assays used to detect this response and populations studied might explain some of these discrepancies. In an attempt to find surrogate markers of the effect of LTBI treatment, it would be important to determine whether, among contacts of patients with contagious tuberculosis, therapy for LTBI could cause changes in MTB-specific immune responses to a variety of RD1-antigens. METHODS AND RESULTS: In a longitudinal study, 44 tuberculin skin test+ recent contacts were followed over a 6-month period and divided according to previous exposure to MTB and LTBI treatment. The following tests which evaluate IFN-gamma responses to RD1 antigens were performed: QuantiFERON TB Gold, RD1 intact protein- and selected peptide-based assays. Among the 24 contacts without previous exposure that completed therapy, we showed a significant decrease of IFN-gamma response in all tests employed. The response to RD1 selected peptides was found to be more markedly decreased compared to that to other RD1 antigens. Conversely, no significant changes in the response to RD1 reagents were found in 9 treated subjects with a known previous exposure to MTB and in 11 untreated controls. CONCLUSION: These data suggest that the effect of INH prophylaxis on RD1-specific T-cell responses may be different based on the population of subjects enrolled (recent infection versus re-infection) and, to a minor extent, on the reagents used.

Region of difference 1 antigen-specific CD4+ memory T cells correlate with a favorable outcome of tuberculosis.

BACKGROUND: Interferon (IFN)-gamma response to region of difference (RD) 1 proteins (culture filtrate 10 and early secreted antigenic target 6) or overlapping peptides is a novel diagnostic marker of tuberculosis (TB) infection. Because we have recently shown that the response to certain peptides selected from RD1 allows discrimination between active TB (A-TB) and successfully treated TB (T-TB), we analyzed here the effector memory T cell profile and RD1-specific responses under the same clinical conditions. METHODS: T cell responses to RD1 antigens were analyzed in patients with either severe or mild A-TB (classified on the basis of radiological lesions) and in 2 sets of healthy control subjects--those who had been successfully treated (the T-TB control subjects) and those whose tuberculin skin test (TST) results were negative (the TST-negative control subjects). IFN-gamma -producing CD4+ effector T cells were monitored by flow-cytometric analysis and ex vivo enzyme-linked immunospot (ELISPOT) assay, whereas a "cultured" ELISPOT assay was used to determine the frequency of memory T cells. RESULTS: In the patients with severe A-TB, both CD4-mediated effector memory and central memory responses to the selected RD1 peptides were almost absent, whereas these responses were found in the majority of the patients with mild A-TB. In contrast, recognition of the selected RD1 peptides was detected in the T-TB control subjects only by expanding the central memory T cell pool. CONCLUSIONS: These data suggest a protective role for RD1 peptide-specific CD4+ effector T cells, which undergo clonal expansion during Mycobacterium tuberculosis replication and then a contraction phase after disease resolution, culminating in the generation of CD4+ memory T cells.

Selected RD1 peptides for active tuberculosis diagnosis: comparison of a gamma interferon whole-blood enzyme-linked immunosorbent assay and an enzyme-linked immunospot assay.

We recently set up a gamma interferon (IFN-gamma) enzyme-linked immunospot assay (ELISPOT), using selected early secreted antigenic target 6 (ESAT-6) peptides, that appears specific for active tuberculosis (A-TB). However, ELISPOT is difficult to automate. Thus, the objective of this study was to determine if the same selected peptides may be used in a technique more suitable for routine work in clinical laboratories, such as whole-blood enzyme-linked immunosorbent assay (WBE). For this purpose, 27 patients with A-TB and 41 control patients were enrolled. Our WBE, using the already described selected peptides from ESAT-6 plus three new ones from culture filtrate protein 10, was performed, and data were compared with those obtained by ELISPOT. Using our selected peptides, IFN-gamma production, evaluated by both WBE and ELISPOT, was significantly higher in patients with A-TB than in controls (P < 0.0001). Statistical analysis showed a good correlation between the results obtained by WBE and ELISPOT (r = 0.80, P < 0.001). To substantiate our data, we compared our WBE results with those obtained by QuantiFERON-TB Gold, a whole-blood assay based on region of difference 1 (RD1) overlapping peptides approved for TB infection diagnosis. We observed a slightly higher sensitivity with QuantiFERON-TB Gold than with our WBE (89% versus 81%); however, our test provided a better specificity result (90% versus 68%). In conclusion, results obtained by WBE based on selected RD1 peptides significantly correlate with those generated by ELISPOT. Moreover, our assay appears more specific for A-TB diagnosis than QuantiFERON-TB Gold, and thus it may represent a complementary tool for A-TB diagnosis for routine use in clinical laboratories.