In colorectal cancer mast cells contribute to systemic regulatory T-cell dysfunction

T-regulatory cells (Treg) and mast cells (MC) are abundant in colorectal cancer (CRC) tumors. Interaction between the two is known to promote immune suppression or loss of Treg functions and autoimmunity. Here, we demonstrate that in both human CRC and murine polyposis the outcome of this interaction is the generation of potently immune suppressive but proinflammatory Treg (DeltaTreg). These Treg shut down IL10, gain potential to express IL17, and switch from suppressing to promoting MC expansion and degranulation. This change is also brought about by direct coculture of MC and Treg, or culture of Treg in medium containing IL6 and IL2. IL6 deficiency in the bone marrow of mice susceptible to polyposis eliminated IL17 production by the polyp infiltrating Treg, but did not significantly affect the growth of polyps or the generation of proinflammatory Treg. IL6-deficient MC could generate proinflammatory Treg. Thus, MC induce Treg to switch function and escalate inflammation in CRC without losing T-cell-suppressive properties. IL6 and IL17 are not needed in this process.

Oligosaccharide-induced whey-specific CD25(+) regulatory T-cells are involved in the suppression of cow milk allergy in mice

Dietary intervention with a unique prebiotic nondigestible carbohydrate mixture has been shown to reduce the development of allergic disease in infants at risk. In this study, the involvement of CD25(+) regulatory T-cells (Treg) in the carbohydrate-induced effects was investigated in mice orally sensitized with whey using adoptive transfer experiments. Donor mice were sensitized with whey and fed a diet containing short-chain galacto-, long-chain fructo- and acidic-oligosaccharides, or a control diet starting 2 wk before sensitization. The acute allergic skin reaction upon intradermal whey challenge was determined and whey-specific Ig were measured. Splenocytes of the donor mice were transferred to naïve recipient mice after partial ex vivo depletion of CD25(+) Treg. The prebiotic diet clearly diminished the acute allergic skin reaction (P < 0.001). Whey-sensitized recipient mice transferred with splenocytes from whey-sensitized, prebiotic-fed donor mice displayed almost complete prevention of the acute allergic skin reaction compared with mice receiving cells from sham-sensitized, prebiotic-fed donor mice (P < 0.001). Partial depletion of CD25(+) T-cells inhibited these effects (P < 0.001), although IgE sensitization was not prevented. This study indicates the involvement of whey-specific CD25(+) Treg in the suppression of the allergic effector response induced by dietary intervention with prebiotics.

Exploring a regulatory role for mast cells: 'MCregs'?

Regulatory cells can mould the fate of the immune response by direct suppression of specific subsets of effector cells, or by redirecting effectors against invading pathogens and infected or neoplastic cells. These functions have been classically, although not exclusively, ascribed to different subsets of T cells. Recently, mast cells have been shown to regulate physiological and pathological immune responses, and thus to act at the interface between innate and adaptive immunity assuming different functions and behaviors at discrete stages of the immune response. Here, we focus on these poorly defined, and sometimes apparently conflicting, functions of mast cells.

Mast cell and T cell communication; amplification and control of adaptive immunity

Recent advances in understanding the physiological role of mast cells (MCs) point to an important regulatory role for these cells in adaptive immunity. MCs express a diverse array of molecules that can promote their interaction with T cells as well as with other immune cells. New evidence demonstrates that mast cells can directly and indirectly communicate with T cells. They can control both effector and regulatory T cell responses and their activity can in turn be modulated by these interactions. Here we briefly summarize these advances and discuss some of the major challenges in understanding the communication of MCs and T cells.

Mast cell modulation of the immune response

Mast cells are present in nearly all vascularized tissues, but not the blood. They are best known for the prominent role they play in atopic disease. However, our current understanding of their direct and indirect roles in the immune response offers a more nuanced picture of both villain and hero. Although they are implicated in many inflammatory disorders, they also defend us from bacterial pathogens, prevent dangerous overreactions by the immune system, and even protect us from snake venom. Perhaps there is more to these maligned cells than we thought.

Mast cell degranulation breaks peripheral tolerance

Mast cells (MC) have been shown to mediate regulatory T-cell (T(reg))-dependent, peripheral allograft tolerance in both skin and cardiac transplants. Furthermore, T(reg) have been implicated in mitigating IgE-mediated MC degranulation, establishing a dynamic, reciprocal relationship between MC and T(reg) in controlling inflammation. In an allograft tolerance model, it is now shown that intragraft or systemic MC degranulation results in the transient loss of T(reg) suppressor activities with the acute, T-cell dependent rejection of established, tolerant allografts. Upon degranulation, MC mediators can be found in the skin, T(reg) rapidly leave the graft, MC accumulate in the regional lymph node and the T(reg) are impaired in the expression of suppressor molecules. Such a dramatic reversal of T(reg) function and tissue distribution by MC degranulation underscores how allergy may causes the transient breakdown of peripheral tolerance and episodes of acute T-cell inflammation.

The role of dendritic cells and regulatory T cells in the regulation of allergic asthma

Airways hyperresponsiveness (AHR) is one of the major clinical features of allergic airways disease including allergic asthma, however the immunological mechanisms leading to the induction and regulation of this disorder are not fully understood. In this review we will summarise the evidence of a number of studies, principally in murine models of AHR, suggesting a central role for respiratory tract dendritic cells (RTDC) in the induction of AHR through the generation of lung-homing, allergen-specific effector T cells. We will also summarise the evidence supporting a role for regulatory T cells in the attenuation of AHR and will propose that, as a counterpoint to their capacity to induce AHR, RTDC may also play a role in the attenuation of AHR through the generation of regulatory T cells (T(reg)). A better understanding of the relationship between the physiological and immunological responses to allergen-induced AHR attenuation, and particularly the role of RTDC and T(reg) in this process, will be essential for the development of new treatments and therapies.

Displaying Fel d1 on virus-like particles prevents reactogenicity despite greatly enhanced immunogenicity: a novel therapy for cat allergy

Allergen-specific desensitization is the only disease-modifying therapy currently available for the treatment of allergies. These therapies require application of allergen over several years and some may induce life-threatening anaphylactic reactions. An ideal vaccine for desensitization should be highly immunogenic and should alleviate allergic symptoms upon few injections while being nonreactogenic. We describe such a vaccine for the treatment of cat allergy, consisting of the major cat allergen Fel d1 coupled to bacteriophage Qβ-derived virus-like particles (Qβ–Fel d1). Qβ–Fel d1 was highly immunogenic, and a single vaccination was sufficient to induce protection against type I allergic reactions. Allergen-specific immunoglobulin G antibodies were shown to be the critical effector molecules and alleviated symptoms by two distinct mechanisms. Although allergen-induced systemic basophil degranulation was inhibited in an FcγRIIb-dependent manner, inhibition of local mast cell degranulation in tissues occurred independently of FcγRIIb. In addition, treatment with Qβ–Fel d1 abolished IgE memory responses upon antigen recall. Despite high immunogenicity, the vaccine was essentially nonreactogenic and vaccination induced neither local nor systemic anaphylactic reactions in sensitized mice. Moreover, Qβ–Fel d1 did not induce degranulation of basophils derived from human volunteers with cat allergies. These data suggest that vaccination with Qβ–Fel d1 may be a safe and effective treatment for cat allergy.

Mast cells down-regulate CD4+CD25+ T regulatory cell suppressor function via histamine H1 receptor interaction

Mast cells promote both innate and acquired immune responses, but little is known about the effect of mast cells on T regulatory (T(reg)) cell function. In this study, we show for the first time that the capacity of murine CD4(+)CD25(+) T(reg) cells to suppress in vitro proliferation by CD4(+)CD25(-) T responder (T(resp)) cells in response to anti-CD3/anti-CD28 mAb-coated beads was reduced in the presence of syngeneic bone marrow-derived mast cells (BMMC) activated by FcepsilonR cross-linking. Activated BMMC culture supernatants or exogenous histamine also inhibited T(reg) cell suppressor function while the histamine H1 receptor-specific antagonist loratadine, but not the H2 receptor-specific antagonist famotidine, restored T(reg) cell suppressor function in the presence of activated BMMC or activated BMMC culture supernatants. Moreover, treatment of T(reg) cells with loratadine, but not famotidine, rescued T(reg) cell suppressor function in the presence of exogenous histamine. In addition, the H1 receptor-specific agonist 2-pyridylethylamine dihydrochloride inhibited T(reg) cell suppressor function to an extent that was comparable to histamine, whereas the H2 receptor-specific agonist amthamine dihydrobromide was without effect. Both T(reg) cells and T(resp) cells expressed H1 receptors. Exposure to histamine caused T(reg) cells to express lower levels of CD25 and the T(reg) cell-specific transcription factor Foxp3. Taken together, these data indicate that BMMC-elaborated histamine inhibited T(reg) cell suppressor function by signaling through the H1 receptor. We suggest that histamine released as a result of mast cell activation by microbial products might cause a transient decrease in T(reg) cell suppressor function, thereby enhancing the development of protective immunity.

The enigmatic role of mast cells in dominant tolerance

PURPOSE OF REVIEW

The role of regulatory T cells (Treg) in peripheral tolerance has been studied extensively in transplantation research. Recently, mast cells have been shown to play an indispensable role in allograft tolerance. The purpose of this review is to inform the reader on the current standings of the role of mast cells in dominant tolerance with an emphasis on the interaction of mast cells with Treg.

RECENT FINDINGS

Mast cells are required to sustain peripheral tolerance via Treg. Treg can stabilize mast cells degranulation by contact-dependent mechanisms through the interaction of OX40 and its ligand OX40L, and by production of soluble factors, such as interleukin-10 and transforming growth factor-beta. Conversely, the activation and subsequent degranulation of mast cells break peripheral tolerance.

SUMMARY

Both mast cells and Treg are needed to create a local immunosuppressive environment in the transplant. Treg are not only necessary to suppress effector T-cell responses but also to stabilize mast cells. Mast cells in return could contribute to the immunosuppressive state by release of transforming growth factor-beta, interleukin-10 and specific proteases. However, the molecular basis for mast cells control of Treg suppression in organ transplantation is still unresolved.

Mast cells counteract regulatory T-cell suppression through interleukin-6 and OX40/OX40L axis toward Th17-cell differentiation

The development of inflammatory diseases implies inactivation of regulatory T (Treg) cells through mechanisms that still are largely unknown. Here we showed that mast cells (MCs), an early source of inflammatory mediators, are able to counteract Treg inhibition over effector T cells. To gain insight into the molecules involved in their interplay, we set up an in vitro system in which all 3 cellular components were put in contact. Reversal of Treg suppression required T cell-derived interleukin-6 (IL-6) and the OX40/OX40L axis. In the presence of activated MCs, concomitant abundance of IL-6 and paucity of Th1/Th2 cytokines skewed Tregs and effector T cells into IL-17-producing T cells (Th17). In vivo analysis of lymph nodes hosting T-cell priming in experimental autoimmune encephalomyelitis revealed activated MCs, Tregs, and Th17 cells displaying tight spatial interactions, further supporting the occurrence of an MC-mediated inhibition of Treg suppression in the establishment of Th17-mediated inflammatory responses.

Cow milk allergy symptoms are reduced in mice fed dietary synbiotics during oral sensitization with whey

Cow milk allergy is the most common food allergy in children. So far, no effective treatment is available to prevent or cure food allergy. The purpose of this study was to compare effects of dietary supplementation with a prebiotic mixture (Immunofortis), a probiotic strain [Bifidobacterium breve M-16V], or a synbiotic diet combining both on the outcome of the allergic response when provided during oral sensitization with whey in mice. Mice were fed diets containing 2% (wt:wt) Immunofortis and/or the B. breve M-16V (n = 6/group). The acute allergic skin response was determined by measuring ear swelling. Antigen-induced anaphylaxis was scored. Furthermore, whey-specific serum immunoglobulins and mouse mast cell protease-1 (mMCP-1) were determined. In mice fed the synbiotic mixture, the allergic skin response and the anaphylactic reaction were strongly reduced compared with whey-sensitized mice fed the control diet (P < 0.01). Immunofortis or B. breve M-16V alone were significantly less effective in reducing the allergic skin response than the synbiotic diet and did not reduce the anaphylactic reaction. The whey-specific IgE and IgG(1) responses were not affected; however, IgG(2a) was greater in all treated groups than in the control group (P < 0.05). Serum mMCP-1 concentrations, reflecting mucosal mast cell degranulation, were lower in mice fed synbiotics compared with those fed the control diet (P < 0.01). Dietary supplementation with Immunofortis, B. breve M-16V, and particularly the synbiotic mixture, provided during sensitization, reduces the allergic effector response in a murine model of IgE-mediated hypersensitivity that mimics the human route of sensitization. This model shows the potential for dietary intervention with synbiotics in reducing the allergic response to food allergens.

Combination of peritumoral mast cells and T-regulatory cells predicts prognosis of hepatocellular carcinoma

The peritumoral inflammatory environment is critical for the progression of intrahepatic recurrence of hepatocellular carcinoma (HCC) after curative resections. Here, we investigated the relevance of peritumoral mast cells (MCs) to HCC outcomes. Peritumoral tryptase(+) MCs in addition to Foxp3(+) T-regulatory cells (Tregs) were evaluated using immunohistochemistry enumeration in tissue microarrays containing 207 randomly selected HCC patients. Clinicopathological factors and postoperative outcomes were compared between high and low subgroups of MCs or Tregs. Compared to low denstiy, higher peritumoral MCs were associated with poorer clinical outcomes, and independently related to elevated 5-year recurrence incidence (54.1%vs 39.2%, P = 0.026). High-dense MCs were especially related to increased probability of early recurrence (within 2 years) (P = 0.004). We also found that peritumoral Tregs were positively correlated with MCs in density (r = 0.353, P < 0.001) and reversely related to HCC outcomes. Notably, MCs in combination with Tregs displayed better prognostic performances than MCs alone (area under curve [AUC](survival) = 0.629 vs 0.589, AUC(recurrence) = 0.632 vs 0.591). Moreover, MCs were positively correlated to alanine aminotransferase, a serum inflammatory marker (P = 0.014). Therefore, peritumoral MCs are promising prognostic parameters for HCC mainly through inflammation response-related mechanisms, and we propose that MCs and Tregs may cooperate with each other and result in poorer prognosis.

T regulatory cells and their counterparts: masters of immune regulation

The interaction of environmental and genetic factors with the immune system can lead to the development of allergic diseases. The essential step in this progress is the generation of allergen-specific CD4(+) T-helper (Th) type 2 cells that mediate several effector functions. The influence of Th2 cytokines leads to the production of allergen-specific IgE antibodies by B cells, development and recruitment of eosinophils, mucus production and bronchial hyperreactivity, as well as tissue homing of other Th2 cells and eosinophils. Meanwhile, Th1 cells may contribute to chronicity and the effector phases. T cells termed T regulatory (Treg) cells, which have immunosuppressive functions and cytokine profiles distinct from that of either Th1 or Th2 cells, have been intensely investigated during the last 13 years. Treg cell response is characterized by an abolished allergen-specific T cell proliferation and the suppressed secretion of Th1 and Th2-type cytokines. Treg cells are able to inhibit the development of allergen-specific Th2 and Th1 cell responses and therefore play an important role in a healthy immune response to allergens. In addition, Treg cells potently suppress IgE production and directly or indirectly suppress the activity of effector cells of allergic inflammation, such as eosinophils, basophils and mast cells. Currently, Treg cells represent an exciting area of research, where understanding the mechanisms of peripheral tolerance to allergens may soon lead to more rational and safer approaches for the prevention and cure of allergic diseases.

Phosphoantigen-activated V gamma 2V delta 2 T cells antagonize IL-2-induced CD4+CD25+Foxp3+ T regulatory cells in mycobacterial infection

Although Foxp3(+) T regulatory cells (Tregs) are well documented for their ability to suppress various immune cells, T-cell subsets capable of counteracting Tregs have not been demonstrated. Here, we assessed phosphoantigen-activated Vgamma2Vdelta2 T cells for the ability to interplay with Tregs in the context of mycobacterial infection. A short-term IL-2 treatment regimen induced marked expansion of CD4(+)CD25(+)Foxp3(+) T cells and subsequent suppression of mycobacterium-driven increases in numbers of Vgamma2Vdelta2 T cells. Surprisingly, activation of Vgamma2Vdelta2 T cells by adding phosphoantigen Picostim to the IL-2 treatment regimen down-regulated IL-2-induced expansion of CD4(+)CD25(+)Foxp3(+) T cells. Consistently, in vitro activation of Vgamma2Vdelta2 T cells by phosphoantigen plus IL-2 down-regulated IL-2-induced expansion of CD4(+)CD25(+)Foxp3(+) T cells. Interestingly, anti-IFN-gamma-neutralizing antibody, not anti-TGF-beta or anti-IL-4, reduced the ability of activated Vgamma2Vdelta2 T cells to down-regulate Tregs, suggesting that autocrine IFN-gamma and its network contributed to Vgamma2Vdelta2 T cells' antagonizing effects. Furthermore, activation of Vgamma2Vdelta2 T cells by Picostim plus IL-2 treatment appeared to reverse Treg-driven suppression of immune responses of phosphoantigen-specific IFNgamma(+) or perforin(+) Vgamma2Vdelta2 T cells and PPD-specific IFNgamma(+)alphabeta T cells. Thus, phos-phoantigen activation of Vgamma2Vdelta2 T cells antagonizes IL-2-induced expansion of Tregs and subsequent suppression of Ag-specific antimicrobial T-cell responses in mycobacterial infection.

IgE receptor and signal transduction in mast cells and basophils

There are many aspects of mast cell and basophil biology that are being explored today. Notably, there is a wide variety of studies of the roles these two cell types play in the development of a multitude of diseases and the role they play in the general immune response. But the original reasons for studying these two cells types--because they are considered crucial to immediate hypersensitivity reactions--remain a driving force for research. These two cell types express the complete high affinity IgE receptor and aggregation of this receptor results in the secretion of multiple potent mediators that cause many of the signs and symptoms of an allergic reaction. Understanding more about the biology of the receptor and the signaling that it initiates remains important to the development of new therapeutic approaches to inhibit this reaction.

Therapeutic immunomodulators from nematode parasites

There has been an alarming increase in the incidence of autoimmune and allergic diseases in Western countries in the past few decades. However, in countries endemic for parasitic helminth infections, such diseases remain relatively rare. Hence, it has been hypothesised that helminths may protect against the development of autoimmunity and allergy. This article reviews the evidence supporting this idea with respect to helminths of the phylum Nematoda (nematodes), considering data from human studies and animal models of inflammatory disease. The nature and mode of action of nematode-derived molecules with immunomodulatory properties are considered, and their therapeutic efficacy in models of autoimmunity and allergy described. The recent and future use of nematodes and their products in treating human disease are also discussed.