Guido Heine

1,25-dihydroxyvitamin D3 promotes IL-10 production in human B cells

1,25‐dihydroxyvitamin D3 (calcitriol) regulates immune responses, e.g., inhibits expression of IgE by B cells and enhances expression of IL‐10 by dendritic cells and T cells. We report here that activation of human B cells by B cell receptor, CD40 and IL‐4 signals induces expression of the gene for 25‐hydroxyvitamin‐D3–1α‐hydroxylase (CYP1α). Accordingly, these B cells generate and secrete significant amounts of calcitriol. In activated B cells calcitriol induces expression of the genes Cyp24, encoding a vitamin D hydroxylase, and Trpv6, encoding a calcium selective channel protein. Calcitriol enhances IL‐10 expression of activated B cells more than threefold, both by recruiting the vitamin D receptor to the promoter of Il‐10, and to lesser extent by modulation of calcium‐dependent signaling. The molecular link in activated B cells between vitamin D signaling, expression of IgE and IL‐10, and their ability to produce calcitriol from its precursor, suggest that pro‐vitamin D (25‐hydroxyvitamin D3) can be used as a modulator of allergic immune responses.

Frequency of contact allergy in German children and adolescents patch tested between 1995 and 2002: results from the Information Network of Departments of Dermatology and the German Contact Dermatitis Research Group

Allergic contact dermatitis (ACD) affects approximately 7% of the general population. To evaluate the frequency of ACD in children, we analysed patch test results collected by the Information Network of Departments of Dermatology between 1995 and 2002. Data of 285 children (6–12 year) and 2175 adolescent patients (13–18 year) were analysed to determine the frequency of sensitization to the 30 most common contact allergens, adjusting for age and sex. As control group, we defined adult patients (60–66 year, n = 7904). The top allergens in children were thimerosal, gentamicin sulphate, nickel‐II‐sulphate, ammoniated mercury, cobalt‐II‐chloride, fragrance mix, bufexamac, Compositae mix, propylene glycol and turpentine. The overall proportion of sensitized patients according to the patch test results was 52.6% in the children group compared to 49.7% in the adolescent group. These findings were similar in the adult group at 52.2%. The detailed analysis regarding sex, occupation, atopy, site of eczema and age showed distinct patterns in each group indicating age‐specific exposures. Atopy‐related diseases were more common in children compared to adults. On the basis of the data of this study, the relationship between atopy and the risk of development of ACD, at least in children, needs further investigation.

Targeting the vitamin D receptor inhibits the B cell-dependent allergic immune response

To cite this article: Hartmann B, Heine G, Babina M, Steinmeyer A, Zügel U, Radbruch A, Worm M. Targeting the vitamin D receptor inhibits the B cell‐dependent allergic immune response. Allergy 2011; 66: 540–548.

Association of the toll-like receptor 2 A-16934T promoter polymorphism with severe atopic dermatitis.

Background:  Atopic dermatitis (AD) is a chronic inflammatory skin disease with a multifactorial pathogenesis and increasing incidence in the Western world. A genetically determined defective function of pattern recognition receptors such as toll‐like receptors (TLRs) has been proposed as a candidate mechanism in the pathogenesis of AD.

Type-IV sensitization profile of individuals with atopic eczema: results from the Information Network of Departments of Dermatology (IVDK) and the German Contact Dermatitis Research Group (DKG)

The role of atopic eczema (AE) as risk factor for the development of allergic contact dermatitis is discussed controversially, as well as its influence on patch test results due to increased irritability. In this study, we analysed the pattern of positive patch test results to most frequent contact allergens in patients with AE (n = 9020) and age matched nonatopic (n = 15 263) individuals. The pattern and the frequencies of the observed sensitizations did not differ greatly from nonatopic individuals. Bufexamac is an exception: in AE patients sensitization is observed three times more often. For the other substances tested only minor differences were detected. Moreover, the frequencies of single, double or polyvalent sensitizations were nearly identical between the two groups. The analysis of the anatomical sites of dermatitis shows differences between the groups: in AE patients, the face (7.2%) and hand dermatitis (6.6%) was more common, and leg dermatitis (4.0%) less common. Analysis of occupation, suspected allergen source, and accompanying factors revealed no major differences between the both groups. Conclusion: The chronic and long‐term exposure to external drugs and emollients presumably carries a risk for sensitization against specific contact allergens in AE patients. However, the sensitization of contact allergens differs surprisingly little between patients with or without AE.

Measurement of Proliferative Responses of Cultured Lymphocytes

Measurement of proliferative responses of human lymphocytes is a fundamental technique for the assessment of their biological responses to various stimuli. Most simply, this involves measurement of the number of cells present in a culture before and after the addition of a stimulating agent. This unit contains several different prototype protocols to induce proliferation in lymphocytes following exposure to mitogens, antigens, allogeneic or autologous cells, or soluble factors. Each of these protocols can be used in conjunction with an accompanying protocol, which contains methods to determine cell proliferation by incorporation of [3H]thymidine into DNA by nonradioactive methods, e.g., reduction of tetrazolium salts (MTT or WST‐1). These protocols provide an estimate of cell proliferation indirectly by measuring DNA synthesis, and cell metabolic activity in an entire cell population, but no data on individual cells is obtained. A protocol for CFSE labeling allows direct detection of single proliferating cells and facilitates the quantification of cell divisions by flow cytometry according to the respective CFSE‐dilution, and following costaining with fluorescent labeled antibodies, the characterization of subpopulations in the cell culture. Curr. Protoc. Immunol. 94:7.10.1‐7.10.26.

CD40L expression permits CD8+ T cells to execute immunologic helper functions

CD8(+) T cells play an essential role in immunity against intracellular pathogens, with cytotoxicity being considered their major effector mechanism. However, we here demonstrate that a major part of central and effector memory CD8(+) T cells expresses CD40L, one key molecule for CD4(+) T-cell-mediated help. CD40L(+) CD8(+) T cells are detectable among human antigen-specific immune responses, including pathogens such as influenza and yellow fever virus. CD40L(+) CD8(+) T cells display potent helper functions in vitro and in vivo, such as activation of antigen-presenting cells, and exhibit a cytokine expression signature similar to CD4(+) T cells and unrelated to cytotoxic CD8(+) T cells. The broad occurrence of CD40L(+) CD8(+) T cells in cellular immunity implicates that helper functions are not only executed by major histocompatibility complex (MHC) class II-restricted CD4(+) helper T cells but are also a common feature of MHC class I-restricted CD8(+) T cell responses. Due to their versatile functional capacities, human CD40L(+) CD8(+) T cells are promising candidate cells for immune therapies, particularly when CD4(+) T-cell help or pathogen-associated molecular pattern signals are limited.

Liver X Receptors Control IgE Expression in B Cells

B lymphocytes play a fundamental role in the development of IgE-dependent allergic immune reactions. Upon appropriate activation, IgE class switch recombination is initiated in B cells, followed by terminal differentiation to IgE-secreting plasmablasts. This process is controlled by different nuclear receptors, including receptors for vitamin D, retinoids, and peroxisome proliferator-activated receptor-γ ligands. In this study, we show constitutive expression of the nuclear liver X receptor (LXR)α and LXRβ in peripheral human B cells. Activation of LXRs reduced secreted IgE (−68% ± 11) in CD40 and IL-4 activated B cells. The production of other isotypes, including IgG, IgM, IgA and B cell homeostatic parameters were not significantly altered by LXR activation. We identified inhibitory action of LXR activation on IgE production involving reduced phosphorylation of JNK and increased membrane CD23 expression (38% ± 11). The biological significance of our findings was validated by showing that systemic treatment of type I-sensitized BALB/c mice with LXR ligands reduced the serum concentrations of Ag-specific IgE in a dose-dependent manner (maximum, −52% ± 14). Thus, our data indicates that LXRs are involved in the control of IgE secretion by differentiating B cells.

Vitamin D receptor binds to the ε germline gene promoter and exhibits transrepressive activity

BACKGROUND Recently, an increased incidence of allergic diseases has been associated with vitamin D deficiency. We demonstrated previously that calcitriol, the active form of vitamin D, inhibits ε germline transcription, a prerequisite for IgE production. However, the underlying mechanisms remain unexplored. OBJECTIVE We sought to investigate whether the ε germline gene promoter (Iε) represents a primary vitamin D receptor (VDR) target. Therefore we investigated VDR binding to Iε, analyzed VDR-complex composition in more detail, and delineated its functional consequences. METHODS The VDR binding to Iε in human B cells, the composition of the VDR-recruited complex, and the acetylation pattern were investigated by means of chromatin immunoprecipitation. The calcitriol-mediated action on Iε was analyzed by using a reporter gene assay. RESULTS We demonstrate that Iε is a possible VDR target. Calcitriol-activated VDR binds together with retinoid X receptor α to the Iε region. The heterodimer interacts with silencing mediator for retinoid and thyroid hormone receptors, which recruits histone deacetylase (HDAC) 1 and HDAC3. The inhibition of silencing mediator for retinoid and thyroid hormone receptors or HDACs reversed the site-specific deacetylation of histones 3 and 4 and the calcitriol-driven inhibition of the ε germline transcription. The VDR-complex transrepressive actions on Iε were confirmed in a reporter assay. CONCLUSION We show here that inhibition of IgE production by calcitriol is mediated by its transrepressive activity through the VDR-corepressor complex affecting chromatin compacting around the Iε region. Our findings shed new light on mechanisms of VDR transrepression and understanding of IgE regulation.

Autocrine IL-10 promotes human B-cell differentiation into IgM- or IgG-secreting plasmablasts

B‐cell‐derived interleukin‐10 (IL‐10) is known to act in a paracrine fashion to suppress inflammation. Here, we show that IL‐10 also acts in an autocrine manner to regulate the differentiation of activated human B cells. We report that IL‐10 expression is not restricted to a dedicated B‐cell subset, but is induced transiently in peripheral human naïve, memory, and CD5+ B cells alike upon activation. Global transcriptome comparison of activated human B cells, secreting IL‐10 or not, identified 138 differentially regulated genes, most of which were associated with differentiation into antibody‐secreting cells and reflecting autocrine IL‐10 signaling. We monitored the differentiation of IL‐10‐secreting B cells and determined the effect of IL‐10‐blocking antibodies against its autocrine and paracrine signaling. IL‐10 signaling promoted the differentiation of activated IL‐10‐secreting B cells into IgM‐ or IgG‐secreting cells, but was dispensable for IgA secretion. Our data imply that B‐cell‐derived IL‐10 not only suppresses immune reactions via paracrine mechanisms, but can also contribute to the differentiation of IL‐10‐secreting B cells into IgM‐ and IgG‐secreting plasmablasts through both autocrine and paracrine signaling.