Decreased AIRE expression and global thymic hypofunction in Down syndrome.

The Down syndrome (DS) immune phenotype is characterized by thymus hypotrophy, higher propensity to organ-specific autoimmune disorders, and higher susceptibility to infections, among other features. Considering that AIRE (autoimmune regulator) is located on 21q22.3, we analyzed protein and gene expression in surgically removed thymuses from 14 DS patients with congenital heart defects, who were compared with 42 age-matched controls with heart anomaly as an isolated malformation. Immunohistochemistry revealed 70.48 ± 49.59 AIRE-positive cells/mm(2) in DS versus 154.70 ± 61.16 AIRE-positive cells/mm(2) in controls (p < 0.0001), and quantitative PCR as well as DNA microarray data confirmed those results. The number of FOXP3-positive cells/mm(2) was equivalent in both groups. Thymus transcriptome analysis showed 407 genes significantly hypoexpressed in DS, most of which were related, according to network transcriptional analysis (FunNet), to cell division and to immunity. Immune response-related genes included those involved in 1) Ag processing and presentation (HLA-DQB1, HLA-DRB3, CD1A, CD1B, CD1C, ERAP) and 2) thymic T cell differentiation (IL2RG, RAG2, CD3D, CD3E, PRDX2, CDK6) and selection (SH2D1A, CD74). It is noteworthy that relevant AIRE-partner genes, such as TOP2A, LAMNB1, and NUP93, were found hypoexpressed in DNA microarrays and quantitative real-time PCR analyses. These findings on global thymic hypofunction in DS revealed molecular mechanisms underlying DS immune phenotype and strongly suggest that DS immune abnormalities are present since early development, rather than being a consequence of precocious aging, as widely hypothesized. Thus, DS should be considered as a non-monogenic primary immunodeficiency.

IgG from atopic dermatitis patients induces IL-17 and IL-10 production in infant intrathymic TCD4 and TCD8 cells.

INTRODUCTION: Our group recently demonstrated that IgG modulates αßT cell cytokine production during the maturation process in the human thymus. The effects of this modulation are IgG repertoire dependent and can exert a systemic and long-term impact. OBJECTIVE: To investigate whether IgG from atopic dermatitis (AD) patients can modulate cytokine production of infant intrathymic TCD4 and TCD8 cells in vitro. METHODS: Thymic tissues were obtained from newborn children from nonatopic mothers, and thymocytes were cultured for 6 days with purified IgG from AD patients or with intravenous immunoglobulin (IVIG) or mock conditions as controls. Cells were gated as double positive T cells (TDP- CD4+ CD8+ ), TCD4 cells (CD4+ CD8- ), or TCD8 cells (CD4- CD8+ ), and intracellular levels of IL-17A, IFN-γ, TNF-α, IL-4, IL-10, and TGF-ß were evaluated by flow cytometry. RESULTS: Compared to mock and IVIG culture conditions, IgG of AD individuals induced in vitro intracellular production of IL-17 and IL-10 by intrathymic TDP, TCD4, and TCD8 cells of infants. TGF-ß was also detected at a higher frequency in response to AD IgG in TDP and TCD8 cells compared to mock and IVIG cultured conditions. An opposite effect was detected upon IFN-γ production in TCD4 cells, such that AD IgG reduced IFN-γ production compared to production under mock conditions but not under IVIG conditions. CONCLUSION: IgG of AD patients can stimulate cytokine production in infant thymocytes and thus resembles the peripheral profile observed in adults. These findings suggest a novel mechanism that can contribute to AD pathogenesis.

Low doses of IgG from atopic individuals can modulate in vitro IFN-γ production by human intra-thymic TCD4 and TCD8 cells: An IVIg comparative approach.

The regulatory effect of allergic responses induced by IgG antibodies on human intra-thymic cells has not been reported in the literature. The aim of this study was to evaluate the possible differential effect of purified IgG from atopic and non-atopic individuals on human intra-thymic αßT cell cytokine production. Thymic tissues were obtained from 14 patients who were less than 7 d old. Additionally, blood samples were collected from atopic and non-atopic volunteers. Thymocytes and peripheral blood mononuclear cells were cultured with purified atopic or non-atopic IgG, and intracellular cytokine production was assessed. Purified IgG did not influence the frequency or viability of human intra-thymic αßT cells. Purified non-atopic IgG induced greater IFN-γ production by intra-thymic CD4+CD8+ T cells than did the mock treatment and atopic IgG. A similar effect of purified non-atopic IgG on TCD8 cells was observed compared with the mock treatment. Atopic IgG inhibited IFN-γ and TGF-ß production by intra-thymic TCD4 cells. Treatment with intravenous immunoglobulin resulted in intermediate levels of IFN-γ and TGF-ß in intra-thymic TCD4 cells compared with treatment with atopic and non-atopic IgG. Peripheral TCD4 cells from non-atopic individuals produced IFN-γ only in response to atopic IgG. This report describes novel evidence revealing that IgG from atopic individuals may influence intracellular IFN-γ production by intra-thymic αßT cells in a manner that may favor allergy development.

Constitutive expression of genes encoding notch receptors and ligands in developing lymphocytes, nTreg cells and dendritic cells in the human thymus.

The thymus is the site of T cell maturation. Notch receptors (Notch1-4) and ligands (DLL1-3 and Jagged1-2) constitute one of several pathways involved in this process. Our data revealed differential constitutive expression of Notch genes and ligands in T lymphocytes and thymic dendritic cells (tDCs), suggesting their participation in human thymocyte maturation. nTreg analyses indicated that the Notch components function in parallel to promote maturation in the thymus.