Modification of the human allergic immune response by allergen-DNA-transfected dendritic cells in vitro

BACKGROUND: Atopic-allergic diseases are characterized by T(H)2-dominated immune responses, resulting in IgE production. DNA-based immunotherapies have been shown to shift the immune response toward a T(H)1-type response in animal models. OBJECTIVE: The aim of the study was to analyze whether dendritic cells (DCs) transfected with allergen-DNA conjugates are able to stimulate human autologous CD4(+) T cells, CD8(+) T cells, or both from atopic individuals to produce T(H)1 cytokines instead of T(H)2 cytokines. METHODS: For this purpose, human mature DCs from atopic donors were transfected with an adenovirus encoding the allergen Phl p 1. Autologous CD4(+) and CD8(+) T cells were stimulated with these transfected DCs, and proliferation and cytokine production were measured. RESULTS: By using an adenoviral vector, a transfection rate of 92% could be achieved. The proliferative response of CD4(+) T cells stimulated with autologous transfected DCs was concentration dependent and almost as high as that of T cells stimulated with mature allergen-pulsed DCs. The proliferation of CD8(+) T cells stimulated with transfected DCs, however, was higher than that of cells stimulated with allergen-pulsed DCs. The cytokine pattern showed a shift toward a T(H)1 immune response compared with T cells stimulated with allergen-pulsed DCs. CONCLUSIONS: Human DCs can be transfected with allergen-DNA conjugates very efficiently by using an adenoviral vector yielding DCs with high T-cell stimulatory capacities, directing the atopic-allergic immune response from T(H)2 dominance toward T(H)1 dominance.     

Regulatory activity of human CD4 CD25 T cells depends on allergen concentration, type of allergen and atopy status of the donor

Regulatory CD4+ CD25+ FoxP3-positive T cells (Treg) are functional in most atopic patients with allergic rhinitis and are able to inhibit T helper type 1 (Th1) and Th2 cytokine production of CD4+ CD25- T cells. This study was designed to analyse the following additional aspects: influence of allergen concentration, influence of the type of allergen, and influence of the atopy status of the donor on the strength of the regulatory activity. CD4+ CD25- T cells from healthy non-atopic controls or from grass-pollen-allergic or wasp-venom-allergic donors were stimulated alone or in the presence of Treg with autologous mature monocyte-derived dendritic cells which were pulsed with different concentrations of the respective allergens. Treg from grass-pollen-allergic donors failed to inhibit proliferation but not cytokine production of CD4+ CD25- T cells at high antigen doses while Treg from non-atopic donors did not fail at these allergen concentrations. Proliferative responses and cytokine production of CD4+ CD25- T cells from most of the examined wasp-venom-allergic patients were not inhibited at any concentration of wasp venom. The use of wasp venom- or phospholipase A2-pulsed dendritic cells for stimulation of CD4+ CD25- T cells from donors who were not allergic to wasp stings only resulted in an inhibited proliferation and Th2 cytokine production by Treg at 10-fold lower than the optimal concentration, while interferon-gamma production was inhibited at all concentrations investigated. These data demonstrate that in allergic diseases the function of Treg is dependent on the concentration and the type of the respective allergen with different thresholds for individual allergens and patients.     

Comparison of allergen-stimulated dendritic cells from atopic and nonatopic donors dissecting their effect on autologous naive and memory T helper cells of such donors

BACKGROUND: Because of their production of IL-12, mature dendritic cells (DC) are potent inducers of T(H)1 responses. However, recent reports have demonstrated that DCs can also induce T(H)2 differentiation. OBJECTIVE: In the current study we investigated which immune response is induced by DCs in naive CD45RA(+) or memory CD45R0(+) CD4(+) T cells from atopic individuals (patients with grass pollen, birch pollen, or house dust mite allergy) compared with nonatopic control subjects. METHODS: Immature DCs, generated from peripheral blood monocytes from atopic and nonatopic donors, were pulsed with the respective allergen and fully matured. Then the mature DCs were cocultured in vitro with autologous naive (CD45RA(+)) and memory (CD45R0(+)) CD4(+) T cells and cytokine and IgE production were measured by ELISA. RESULTS: After the second restimulation with allergen-pulsed DCs, naive as well as memory autologous CD4(+) T cells from atopic but not from nonatopic donors showed an enhanced production of the T(H)2-type cytokines IL-4, IL-5, and IL-10, resulting in an increased IgE production, whereas IFN-gamma production and proliferation were not different. IL-12 production and surface marker expression of DCs derived from atopic and nonatopic donors did not differ and addition of neutralizing anti-IL-12 mAbs did not increase IL-4 but diminished IFN-gamma production. CONCLUSION: These data indicate that mature DCs are able to induce naive and activate allergen-specific T helper cells to produce T(H)2 cytokines if the T cells are derived from atopic donors. This phenomenon is not due to diminished IL-12 production by DCs of atopic donors.     

Inhibition of human allergic T-helper type 2 immune responses by induced regulatory T cells requires the combination of interleukin-10-treated dendritic cells and transforming growth factor-β for their induction

BACKGROUND: In grass pollen-allergic individuals, T cell anergy can be induced by IL-10-treated dendritic cells (IL-10-DC) resulting in the suppression of T helper type 1 (Th1) as well as Th2 cells. This study was performed to analyse whether such IL-10-DC-treated T cells are able to act as regulatory T cells (Treg) suppressing the function of other T cells in the periphery. As transforming growth factor (TGF)-beta is also a potential inducer of Treg, we additionally analysed the inhibitory capacity of TGF-beta-treated T cells in this system. MATERIALS AND METHODS: Freshly isolated CD4+ or CD4+ CD25- T cells from grass pollen-allergic donors were stimulated with autologous mature monocyte-derived allergen-pulsed DC in the presence or absence of T cells previously cultured with IL-10-DC- and/or TGF-beta. RESULTS: Anergic T cells induced by allergen-pulsed IL-10-treated DC or allergen-pulsed DC and TGF-beta enhanced IL-10 production and strongly inhibited IFN-gamma production of freshly prepared peripheral CD4+ or CD4+ CD25- T cells while proliferation and Th2 cytokine production were only slightly reduced. The combination of allergen-pulsed IL-10-treated DC and TGF-beta had an additional effect leading to a significant suppression also of Th2 cytokine production and proliferation. Suppression was not antigen-specific and was mainly mediated by cell-to-cell contact and by the molecule-programmed death-1 and only partially by CTLA-4, TGF-beta and IL-10. CONCLUSION: These data demonstrate that regulatory T cells that also suppress Th2 cytokine production are induced by two signals: TGF-beta and IL-10-DC. This is of importance for the regulation of allergic immune responses and might be exploited for future therapeutic strategies for allergic diseases.     

Treatment of autoimmune diseases in MRL/lpr mice by allogenic bone marrow transplantation plus adult thymus transplantation

CD1d-restricted invariant natural killer T (iNK T) cells activated by their experimental ligand alpha-galactosylceramide (alpha-GC) can produce both T helper 1 (Th1) and Th2 cytokines and display regulatory functions. Recent studies identified CD4(+) and CD4(-) CD8(-) double-negative (DN) iNK T cells as the two major components of the human population and suggest that they display a Th2 and a Th1 profile, respectively. We compared the Th2-promoting activity of freshly isolated human CD4(+) and DN iNK T cells in terms of their capacity to induce Ig production by autologous B cells. Secretion of IgG and IgE but not IgM was enhanced by the CD4(+) T cell subset (including iNK T cells) but not by its DN counterpart. iNK T cells were directly responsible for this pro-Th2 effect, as demonstrated by the requirement for both alpha-GC stimulation and CD1d presentation, as well as by its disappearance upon iNK T cell depletion. Interaction with iNK T cells led to progressive accumulation of isotype-switched and activated B cells. Myeloid dendritic cells (DC) completely block the induction of Ig production in co-culture. This dominant inhibitory effect of myeloid DC was concomitant with a specific loss of interleukin (IL)-4 production by CD4(+) iNK T but not by conventional T cells. These data support the conclusion that, conversely to the interferon (IFN)-gamma-producing DN human iNK T cell population, interleukin (IL)-4-producing CD4(+) iNK T cells can activate and help B cells to produce both IgG and IgE through a CD1d-dependent mechanism, in keeping with a functional Th1/Th2 dichotomy between these subsets.     

Allergological implication of the quaternary hexameric structure of the cockroach allergen Per a 3

Background Cockroach allergens play a very important role in allergic diseases, especially asthma. The major allergen of the American cockroach (Periplaneta americana), Per a 3, naturally occurs as isoforms of hexamers. Objective The aim of this study was to investigate whether the hexameric structures of Per a 3 influence their allergenicity and immunogenicity. Methods Therefore, we compared the different effects of native hexamers and dissociated monomers of cockroach haemolymph (HL), containing almost only Per a 3 proteins (HL‐Per a 3), on proliferation and T‐helper type 1 (Th1)/Th2 cytokine production of human CD4⁺ T cells in co‐culture with allergen‐pulsed monocyte‐derived autologous dendritic cells (DC) as well as the leukotriene release of basophils. Results In P. americana‐sensitized and non‐sensitized donors the HL‐Per a 3 monomers were internalized faster by immature DC and induced higher proliferation and IFN‐γ production than the hexamers. While in non‐sensitized donors IL‐4 and IL‐5 as well as IL‐10 production were also increased after stimulation with monomeric HL‐Per a 3‐pulsed DC, Th2 cytokine and IL‐10 production were only enhanced in P. americana‐sensitized donors using hexameric HL‐Per a 3‐pulsed DC. Furthermore, in the leukotriene release assay the monomers were less effective than the hexamers. Conclusion Our data indicate that the quaternary structure can influence both allergenicity and immunogenicity, also depending on the sensitization status. The monomeric variant of Per a 3 allergens could be a possible candidate for a specific immunotherapy because the IgE‐mediated allergic reaction and the Th2‐inducing capacity are diminished while the Th1‐inducing capacity is retained.     

Allergen-specific immune deviation from a TH2 to a TH1 response induced by dendritic cells and collagen type I.

BACKGROUND: Atopy and IgE production are associated with enhanced allergen-specific T(H)2 responses. Therefore a causative treatment may result from the deviation of this T(H)2-dominated immune response toward a T(H)1 response. OBJECTIVE: This study was carried out to analyze whether dendritic cells, the most potent antigen-presenting cells that are also known to induce antigen-specific T(H)1 responses, are suitable for therapy of atopic diseases by shifting the allergen-specific T(H)2 response toward a T(H)1 response. METHODS: Monocyte-derived dendritic cells were used to present allergens in vitro to autologous CD4(+) T cells of allergic persons. Because collagen type I activates dendritic cells and enhances the secretion of IL-12, we performed allergen presentation assays also in the presence of collagen type I. RESULTS: After stimulation with allergen-pulsed dendritic cells the production of IFN-gamma as well as that of IL-4 and IL-5 by CD4(+) T cells was enhanced. In the presence of collagen type I, however, a significant shift toward a T(H)1 response with increased production of IFN-gamma and a decreased production of IL-5 could be observed. When T cells were stimulated directly with anti-CD3 and anti-CD28 in the absence of antigen-presenting cells, it was demonstrated that collagen type I also exerted a direct effect on T cells, increasing their IFN-gamma production. CONCLUSION: These data indicate that collagen type I influences dendritic cells as well as T cells in a way that a shift in cytokine production results in a T(H)1 response even in already-sensitized atopic individuals.     

Dendritic cells from Chlamydia-infected mice show altered Toll-like receptor expression and play a crucial role in inhibition of allergic responses to ovalbumin

Our previous study has shown that Chlamydia lung infection can inhibit local eosinophilic inflammation induced by allergen sensitization and challenge, which is correlated with altered cytokine production. In the present study, we examined the role played by dendritic cells (DC) in chlamydial infection-mediated modulation of allergic responses. The results showed that DC freshly isolated from Chlamydia-infected mice (iIDC), unlike those from naive control mice (iNDC), could efficiently modulate immune responses to ovalbumin in vitro and in vivo. Co-culture of freshly isolated DC with naive CD4 cells from T cell receptor transgenic mice (DO11.10) showed that iIDC directed Th1-dominant, while iNDC directed Th2-dominant, allergen-specific CD4 T cell responses. Moreover, adoptive transfer of iIDC, but not iNDC, could inhibit systemic and local eosinophilia induced by allergen exposure. The reduction of eosinophilia was associated with a decrease in IL-5 receptor expression on bone marrow cells and the production of IL-5 and IL-13 by T lymphocytes. Analysis of the DC showed that iIDC expressed significantly higher levels of mRNA for Toll-like receptor 9 and produced more IL-12 compared to iNDC. The data demonstrate a critical role played by DC in infection-mediated inhibition of allergic responses.     

Augmented Phl p 5-specific Th2 response after exposure of dendritic cells to allergen in complex with specific IgE compared to IgG1 and IgG4

In this study we have elucidated the effects of allergen-specific antibodies on human DCs and T-cells. Monocyte-derived DCs from allergic patients were exposed to Phl p 5 alone or in complex with Phl p 5-specific human IgG1, IgG4 or IgE and further co-cultured with autologous memory CD4(+) T-cells. We demonstrate that DCs treated with Phl p 5/IgE-complexes secrete higher levels of IL-1alpha, IL-6, VEGF and MCP-3 compared to Phl p 5 alone. Furthermore, we show that the ability of DCs to present allergen to memory CD4(+) T-cells and induce a Th2 cytokine profile is significantly augmented when the uptake is mediated by specific IgE antibodies, whereas IgG1 and IgG4 have no such effect. The differences in cytokine profiles depending on the antibody subtype could partly explain the ability of allergic individuals to amplify allergen-specific immune response and could thus be involved in the etiology of allergic responses.     

Dendritic cells are decreased in blood and accumulated in granuloma in tuberculosis

Immunity against tuberculosis consists of innate and adaptive immune responses. In this study, we investigated the dynamics of dendritic cells (DC), which are known to elicit a variety of immune responses, in patients with tuberculosis. CD11c(+) peripheral blood DC were decreased in patients with tuberculosis. Immunohistochemical analyses demonstrated that a number of fascin(+), CD11c(+), HLA-DR(+) DC were infiltrating the lymphocyte areas of the tuberculous granulomas (tubercles). Immunohistochemical analyses also demonstrated that interferon-gamma-producing Th1 cells were increased in the tubercles of the patients, indicating the presence of Th1 polarization at least in the context of inflammatory tissues. In vitro coculture of autologous naive T cells with CD11c(+) or CD11c(-) DC pretreated with Bacillus Calmette Guérin augmented the production of Th1 cells. These findings suggested that the trafficking of DC from the peripheral blood into the tubercles causes a dominant Th1 balance and thus plays an essential role in the immunity against tuberculosis.     

gammadelta T cells contribute to the systemic immunoglobulin E response and local B-cell reactivity in allergic eosinophilic airway inflammation

Allergic airway inflammation induced in mice is T-cell dependent and recruitment of eosinophils to airspaces requires both alphabeta and gammadelta T cells. From previous studies it is evident that alphabeta T cells are essential for the allergic T helper type 2 (Th2)-like response, while the mechanistic contribution of gammadelta T cells is still unclear. In this study, we have investigated the role of gammadelta T cells in allergic airway eosinophilia induced by ovalbumin hypersensitivity. By comparing the responsiveness to sensitizing allergen of wild-type mice with that of T-cell receptor gammadelta knockout mice (TCRgammadelta KO) we demonstrated that mice lacking gammadelta T cells are defective in the systemic ovalbumin-specific immunoglobulin E (IgE) response. Furthermore, after aerosol challenge with allergen, gammadelta T-cell deficient mice exhibited a significantly decreased migration of B cells and natural killer cells to airways and reduced levels of allergen-specific IgG and IgA in bronchoalveolar lavage fluid. The role for B cells in the airway inflammation was indicated by the impaired ability of mice lacking functional B cells to evoke an eosinophilic response. The diminished eosinophilia in TCRgammadelta KO mice could not be explained by a defective Th2 activation since these mice displayed a normal IgG response in serum and an unaffected IG2b/IgG1 ratio in airways. Analysis of immunoregulatory cytokines in isolated lung tissue, thoracic lymph nodes and spleen further supported the notion that these mice are able to evoke a sufficient activation of T helper cells and that gammadelta T cells are not required for maintaining the Th2 profile. These results indicate that gammadelta T cells contribute to allergic airway inflammation by pathways separate from classical Th2 immune activation.     

Allergen extract-induced interleukin-10 in human memory B cells inhibits immunoglobulin E production

Background Elevated specific IgE antibody levels are common in atopic individuals, caused by T-helper type 2-dominated B cell activation. The induction of antigen-specific IL-10 secreting T cells is discussed as an important mechanism during specific immunotherapy. By contrast the presence and function of B cell-derived IL-10 is not well defined yet.
Objective We investigated whether type-I allergen extracts induce IL-10 expression in human B cells and analysed its functional role on IgE production.
Methods Human peripheral B cells were stimulated with grass pollen, house dust mite (HDM) ( Dermatophagoides pteronyssimus ; Der p) and dog allergen extract. Expression of IL-10 by activated human B cells was determined by flow cytometric analysis and ELISA. Functional analysis considering immunoglobulin production was assayed by ELISA.
Results The allergen extracts studied induced IL-10 expression in B cells. However, the ability to induce IL-10 differed between the allergen extracts. The most potent allergen extract was dog (169±28 pg/mL), followed by grass pollen (141±10 pg/mL) and HDM allergen (125±11 pg/mL). Upon allergen extract stimulation only CD27 expressing memory B cells produced IL-10 and co-expressed the very early activation antigen CD69. The addition of allergen extracts to B cells activated by anti-CD40 and IL-4 selectively inhibited IgE which was dependent on allergen extract-induced IL-10. By contrast the other immunoglobulin subclasses like IgA, IgG or IgM were not altered upon allergen extract challenge.
Conclusion Our data indicate that allergen-activated memory B cells can modulate IgE production through secretion of IL-10.     

Der p 1-pulsed myeloid and plasmacytoid dendritic cells from house dust mite-sensitized allergic patients dysregulate the T cell response

Although reports suggest that dendritic cells (DC) are involved in the allergic reaction characterized by a T helper cell type 2 (Th2) profile, the role of myeloid (M-DC) and plasmacytoid DC (P-DC), controlling the balance Th1/Th2, remains unknown. Here, we showed that in Dermatophagoides pteronyssinus (Dpt)-sensitized allergic patients and in healthy donors, M-DC displayed a higher capacity to capture Der p 1, a major allergen of Dpt, than did P-DC. However, Der p 1-pulsed M-DC from healthy subjects overexpressed CD80 and secreted interleukin (IL)-10, whereas M-DC from allergic patients did not. In contrast, with Der p 1-pulsed P-DC from both groups, no increase in human leukocyte antigen-DR, CD80, and CD86 and no IL-10 secretion were detected. When cocultured with allogeneic naive CD4(+) T cells from healthy donors, Der p 1-pulsed M-DC from allergic patients favored a Th1 profile [interferon (IFN)-gamma(high)/IL-4(low)] and Der p 1-pulsed P-DC, a Th2 profile (IFN-gamma(low)/IL-4(high)). In healthy donors, no T cell polarization (IFN-gamma(low)/IL-4(low)) was induced by Der p 1-pulsed M-DC or P-DC, but in response to Der p 1-pulsed M-DC, T cells secreted IL-10. The neutralization of IL-10 produced by Der p 1-pulsed M-DC from healthy donors led to an inhibition of IL-10 production by T cells and a polarization toward a type 1. Thus, IL-10 produced by M-DC might be an essential mediator controlling the balance between tolerance and allergic status. In addition, P-DC could contribute to the steady state in healthy donors or to the development of a Th2 response in allergic donors.     

Adoptive transfer of dendritic cells from allergic mice induces specific immunoglobulin E antibody in naïve recipients in absence of antigen challenge without altering the T helper 1/T helper 2 balance

Dendritic cells (DCs) are important in the regulation of immune responses and it has been proposed that these cells play an important role in asthma; however, their role in food allergy is still largely unknown. Our aim was to study specific immunoglobulin E (IgE) and immunoglobulin G (IgG) responses in naïve recipients following adoptive transfer of myeloid DCs from allergic and control mice. The phenotypic features and lymphokine production of DCs were also investigated. CD11c ^{+ /hi} B220^? DCs isolated from spleen and Peyer's patches (PP) of cow's milk (CM) allergic and control mice were transferred intravenously (i.v.) into naïve syngeneic recipients, and IgE‐ and IgG‐specific responses were evaluated. Experiments were also carried out to determine the levels of interferon‐γ (IFN‐γ) and interleukin (IL)‐4 produced by splenocytes from naïve recipients following the adoptive transfer, and CD40 ligand (CD40L)‐mediated IL‐10 production by DCs from allergic and control mice. DCs isolated from spleen and PP of allergic mice, but not control groups, induced CM‐specific IgG and IgE antibody production in naïve recipients in the absence of previous immunization, but did not modify the T helper 1 (Th1) and T helper 2 (Th2) balance. Furthermore, although no difference was observed in the expression of canonical DC surface markers, PP DCs from allergic mice produced less IL‐10 than DCs from controls. We interpret these data as showing that DCs play a pivotal role in allergen‐specific IgE responses and that a Th2‐skewed response may not be involved in the early phase of allergic responses. The identification of the mechanisms underlying these events may help to design novel strategies of therapeutic intervention in food allergy.     

Interleukin-10-treated dendritic cells do not inhibit Th2 immune responses in ovalbumin/alum-sensitized mice

BACKGROUND: It is well known that the immunoregulatory cytokine interleukin (IL)-10 inhibits the accessory function of human dendritic cells (DC) in vitro. Recently, we have shown that these IL-10 DC inhibit the production of T helper cell 1 (Th1) and T helper cell 2 (Th2) cytokines by T cells from atopic individuals in vitro. The current study was set out to analyze whether IL-10 DC also exert inhibitory effects in vivo in a murine model of allergy to ovalbumin adsorbed to the adjuvant aluminium hydroxide (OVA/alum). METHODS: OVA-pulsed or unpulsed bone marrow-derived DC, treated with IL-10 or left untreated during generation, were injected intravenously into BALB/c mice prior to and during OVA/alum sensitization, and sera and immune responses of mesenterial lymph node cells were analyzed. Additionally, bronchoalveolar lavage was performed after intranasal challenge with OVA. RESULTS: Treatment of BALB/c mice with OVA-pulsed DC led to a significantly enhanced proliferation as well as Th2 (IL-4, IL-5), Th1 (interferon-gamma) and IL-10 cytokine production after restimulation of lymph node cells with OVA in vitro compared with OVA immunization alone. In contrast, using OVA-pulsed IL-10 DC for transfer, proliferation and cytokine production by lymph node cells were not enhanced. OVA-specific immunoglobulin G1 (IgG1) and IgG2a production were significantly increased after transfer of OVA-pulsed DC and OVA-pulsed IL-10 DC, respectively, whereas anti-OVA IgE production and airway eosinophilia remained unchanged. CONCLUSIONS: Our data indicate that IL-10 treatment of DC decreases the Th1 and Th2 stimulatory capacity of DC but does not actually inhibit systemic (IgE) and local (airway inflammation) allergen-specific immune responses in a murine model of allergy.     

CD8+ immunoregulatory cells in the graft-versus-host reaction: CD8 T cells activate dendritic cells to secrete interleukin-12/interleukin-18 and induce T helper 1 autoantibody

Initiation of cell-mediated immunity or autoimmunity requires secretion of interleukin (IL)-12 from dendritic cells (DC), which drives the generation of T helper 1 (Th1) effector cells in synergy with IL-18. Induction of IL-12 can be triggered by microbial stimuli but also requires signals from activated T cells. We investigated interactions between alloreactive CD4 and CD8 T cells in mixed lymphocyte reactions (MLR) in vitro and in the graft-versus-host reaction (GVHR) in vivo. In a parent-into-F1 model of GVHR, donor CD8 cells were found to suppress the hyper-immunoglobulin E (IgE) syndrome, anti-DNA immunoglobulin G1 (IgG1) autoantibodies and donor CD4-cell expansion, but were essential for Th1-dependent immunoglobulin G2a (IgG2a) autoantibody production and release of serum IL-12 p40. In vitro, addition of alloreactive CD8 cells to CD4 cells and mature DC enhanced Th1 development. CD4 and CD8 T cells induced IL-18 from DC and primed for IL-12 p70 secretion via interferon-gamma (IFN-gamma) or tumour necrosis factor-alpha (TNF-alpha). However CD8 T cells, but not CD4 cells, released IFN-gamma/TNF-alpha after primary stimulation. The data suggest that rapid release of inflammatory cytokines from central memory-type CD8 cells early in immunity is critical for induction of Th1 cells via DC activation and IL-12 production. This pathway could provide a means for amplification of cell-mediated autoimmunity in the absence of microbial stimuli.     

Adjuvant effects of aluminium hydroxide‐adsorbed allergens and allergoids – differences in vivo and in vitro

Allergen‐specific immunotherapy (SIT) is a clinically effective therapy for immunoglobulin (Ig)E‐mediated allergic diseases. To reduce the risk of IgE‐mediated side effects, chemically modified allergoids have been introduced. Furthermore, adsorbance of allergens to aluminium hydroxide (alum) is widely used to enhance the immune response. The mechanisms behind the adjuvant effect of alum are still not completely understood. In the present study we analysed the effects of alum‐adsorbed allergens and allergoids on their immunogenicity in vitro and in vivo and their ability to activate basophils of allergic donors. Human monocyte derived dendritic cells (DC) were incubated with native Phleum pratense or Betula verrucosa allergen extract or formaldehyde‐ or glutaraldehyde‐modified allergoids, adsorbed or unadsorbed to alum. After maturation, DC were co‐cultivated with autologous CD4⁺ T cells. Allergenicity was tested by leukotriene and histamine release of human basophils. Finally, in‐vivo immunogenicity was analysed by IgG production of immunized mice. T cell proliferation as well as interleukin (IL)‐4, IL‐13, IL‐10 and interferon (IFN)‐γ production were strongly decreased using glutaraldehyde‐modified allergoids, but did not differ between alum‐adsorbed allergens or allergoids and the corresponding unadsorbed preparations. Glutaraldehyde modification also led to a decreased leukotriene and histamine release compared to native allergens, being further decreased by adsorption to alum. In vivo, immunogenicity was reduced for allergoids which could be partly restored by adsorption to alum. Our results suggest that adsorption of native allergens or modified allergoids to alum had no consistent adjuvant effect but led to a reduced allergenicity in vitro, while we observed an adjuvant effect regarding IgG production in vivo.     

NK cell regulation of T cell-mediated responses

NK cells promote adaptive immune responses through their production of type 1 and type 2 cytokines or chemokines. Secretion of these factors by activated NK cells influences the differentiation of B and T lymphocytes. Increasing evidence indicates that NK cells are also directly involved in dendritic cell (DC) maturation. By contrast, a potential role for direct cell-cell interactions between NK and T lymphocytes, in particular CD4(+) T cells, has not been explored. We provide evidence that activated human NK cells are able of promoting TcR-dependent proliferation of resting autologous peripheral blood CD4(+) T cells by a process that involves costimulatory molecules of the immunoglobulin (Ig) and tumor necrosis factor (TNF) superfamilies. These findings suggest a novel link between natural and adaptative immune responses.