The activation of monocyte and T cell networks in patients with bipolar disorder
Highlights
► This manuscript describes the newest T lymphocyte subsets in patients with bipolar disorder and relate these to the classical subsets of the T cell network and to the monocyte inflammatory state.
Introduction
There is accumulating evidence that activation of the immune system plays an important role in the pathogenesis of bipolar disorder (BD). In support of this view we recently described a higher expression of a coherent set of 34 inflammatory genes, an inflammatory gene expression “signature”, in the circulating monocytes of 60–70% of BD patients (Drexhage et al., 2010a, Padmos et al., 2008). Apart from cells of the monocyte lineage, T cells are important contributors to the immune response, but literature on T cell numbers and cytokines in BD is scarce and the aim of the present study is to evaluate T cell related inflammatory networks in relation to monocyte activation state in patients with BD.
Previously we reported on higher numbers of CD25+ and CD71+ (“activated”) T cells in the circulation of BD patients (Breunis et al., 2003), but at present there are no data on the circulating numbers of the various CD4+T helper cell subsets in BD, such as CD4+T helper(h)1 and Th2 cells, though there are data on the serum levels of IFN-γ and IL-4, the hallmark cytokines of these two T cell subsets (Brietzke et al., 2009, Drexhage et al., 2010a, Ortiz-Dominguez et al., 2007). Both higher and unaltered levels of the cytokines have been described.
In recent years a new T helper subset has been discovered, the so-called CD4+ “Th17 cells”, which produce the pro-inflammatory cytokine IL-17 (Bettelli et al., 2008). Th17 cells protect the host against bacteria and fungi by activating macrophages via the production of IL-17 (but also IL-21 and IL-22). In addition Th17 cells play a role in the pathogenesis of autoimmune diseases such as psoriasis and rheumatoid arthritis (Bettelli et al., 2008). Functions of Th17 cells are thus very similar to those of Th1 cells. The inflammation inducing effects of Th1 cells, Th17 cells and of monocytes and macrophages are controlled by a special class of T cells, the regulatory CD4+CD25highFoxP3+ T cells (Hori et al., 2003, Wing and Sakaguchi, 2010). The main function of these natural, inborn, thymus-derived regulatory T cells is tempering the inflammatory response thereby maintaining homeostasis and tolerance to self-antigens. The cytokines involved in this anti-inflammatory action are thought to be TGF-β and IL-10 (though these cytokines are also produced by monocytes/macrophages). Patients lacking CD4+CD25highFoxP3+ natural T regulatory (reg) cells due to a genetic mutation in the gene coding for FoxP3, suffer from a severe and rapidly lethal poly-endocrine auto-immune syndrome (IPEX, Immune dysregulation, Polyendocrinopathy, Enteropathy X-linked syndrome) (Wildin et al., 2002).
Since BD patients have a higher risk to develop endocrine autoimmune diseases, including autoimmune thyroid disease (AITD) (Kupka et al., 2002, Padmos et al., 2004), we had as second aim of this study to investigate whether BD patients with AITD have an imbalanced interplay between inflammation-prone monocytes and an abnormal tuned T cell system, notably abnormal numbers of natural T reg cells.
For this study we were able to use deep frozen leukocytes of 38 BD patients of the previously reported series of 56 BD patients tested for monocyte gene expression (Drexhage et al., 2010b, Padmos et al., 2008, van der Heul-Nieuwenhuijsen et al., 2010) and 22 age and gender matched healthy controls. This enabled us to relate the T cell state to the pro-inflammatory state of the monocytes of the BD patients. TPO-Abs were positive in 11 of the 38 cases (29%).
We determined the percentages of IFN-γ+Th1, IL-4+Th2, IL-17A+Th17 and of CD4+CD25highFoxP3+ regulatory T cells using FACS analysis. Next to these cellular analyses we evaluated the serum levels of the monocyte cytokines PTX3, CCL2, TNF-α, IL-1β IL-6, IL-8, and IL-10, of the shed sCD25 (the IL-2 Receptor, highly expressed on CD4+CD25highFoxP3+ regulatory T cells) and of the T cell cytokines IFN-γ, IL-4, IL-5, IL-17A and IL-22.
Section snippets
Patients with bipolar disorder and controls
The 38 BD subjects tested were the index cases of twin-pairs, which we had used in a previous study, aged 18–60 years, suffering from bipolar I or bipolar II disorder according to DSM-IV criteria (Padmos et al., 2009) (we tested these index BD cases, since we had frozen samples left in store of only these individuals). Material of the co-twins was not used in this study. The recruitment procedure and inclusion criteria have previously been described in (Vonk et al., 2007). In short the BD
Th1. (CD4+IFNγ+), Th2 (CD4+IL4+) and Th17 (CD4+IL17A+) cells in BD patients and HC
We first analyzed by forward and side scatter in FACS (for gating strategy, see Fig. 1) the percentages of total lymphocytes and monocytes in the PBMC preparations of the BD patients and healthy controls (HC). There were no differences in the percentages of monocytes and lymphocytes between BD and HC (data not shown).
Subsequently, we quantified after stimulation with PMA and ionomycin for 4 h (a procedure to activate lymphocytes) the percentages of the Th1, Th2 and Th17 cells. There were no
Discussion
This study shows significantly higher levels of sCD25 and higher percentages of circulating CD4+CD25highFoxP3+ regulatory T cells in the circulation of BD patients, the latter only in BD patients less than 40 years of age and in BD patients without signs of AITD.
The BD patients with AITD lacked the increase in CD4+CD25highFoxP3+ regulatory T cells and were additionally characterized by high circulating percentages of Th1 cells (though the latter not significant). Although in this relatively
Conflict of interest
H.A. Drexhage has received grants from the Netherlands Organisation for Health Research and Development, the European Union, the Stanley Medical Research Institute, the Dutch Diabetic Foundation and the JDRF; he has received speaker’s fees from Astra Zenica and he serves/has served in advisory boards of the Netherlands Organisation for Health Research and Development, the European Union and the JDRF.
W.A. Nolen has received grants from the Netherlands Organisation for Health Research and
Acknowledgments
We thank Alberto Mantovani for providing the PTX3 ELISA, Harm de Wit and Annemarie Wijkhuijs for their excellent technical assistance, Caspar Looman for statistical advice and Sandra de Bruin for help with designing the figures.
References (30)
- et al.
High numbers of circulating activated T cells and raised levels of serum IL-2 receptor in bipolar disorder
Biol. Psychiatry
(2003) - et al.
Comparison of cytokine levels in depressed, manic and euthymic patients with bipolar disorder
J Affect Disord.
(2009) - et al.
Are regulatory T-cells linked with aging?
Exp. Gerontol.
(2006) - et al.
Cytokines in schizophrenia and the effects of antipsychotic drugs
Brain Behav. Immun.
(2006) - et al.
Cytokine levels in euthymic bipolar patients
J Affect Disord.
(2010) - et al.
Monocyte-derived dendritic cells in bipolar disorder
Biol. Psychiatry
(2006) - et al.
High rate of autoimmune thyroiditis in bipolar disorder: lack of association with lithium exposure
Biol. Psychiatry
(2002) - et al.
Immunologic variables in acute mania of bipolar disorder
J. Neuroimmunol.
(2004) - et al.
A high prevalence of organ-specific autoimmunity in patients with bipolar disorder
Biol. Psychiatry
(2004) - et al.
Effects of antipsychotic drugs on cytokine networks
J. Psychiatr. Res.
(2000)