IL-33 and IgE stimulate mast cell production of IL-2 and regulatory T cell expansion in allergic dermatitis.

BACKGROUND: We have previously shown that mast cells (MCs) suppress chronic allergic dermatitis in mice. The underlying mechanism involves MC-derived IL-2, which supports regulatory T cell (Treg) response at the site of inflammation. However, it is not clear what are the factors that drive MCs to produce IL-2. OBJECTIVE: To understand the mechanisms that lead to IL-2 production from MCs in chronic allergic dermatitis. METHODS: Isolated murine bone marrow-derived MCs (BMMCs) were incubated with various stimulators, and IL-2 production was assessed by RT-PCR and ELISA. The response of signalling pathways was evaluated by MAPK inhibitors and Western blot analysis. The effect of MC-IL-2 on Tregs was studied by incubation of splenic T cells with conditioned media obtained from activated BMMCs. Dermatitis was elicited by repeated exposures of mouse ears to oxazolone. MCs in mouse and human skin samples were evaluated by immunostaining. RESULTS: BMMCs released IL-2 in response to IL-33, and IL-2 production was further enhanced by concomitant FcεRI activation. The effect of IL-33 was mediated by activation of the MAPK family members. IL-2 in conditioned media from IL-33 and IgE-stimulated BMMCs led to considerable expansion of Tregs in vitro. IL-33 levels were elevated in oxazolone-challenged ears along with increased numbers of IL-2-expressing MCs. Human skin with chronic inflammation also contained IL-2-expressing MCs that colocalized with IL-33 staining in the dermis. CONCLUSIONS: IL-33, in collaboration with IgE, is critical for MC-IL-2 production in allergic skin disease, thus leading to Treg stimulation and suppression of allergic dermatitis.

Oncostatin M in bronchoalveolar lavage correlates with the severity of sarcoidosis.

BACKGROUND: Recent studies have shown that oncostatin M (OSM) might have a role in T cell-mediated inflammatory processes in which mast cells are also involved. Patients with severe sarcoidosis might develop fibrotic changes in the lung. We assessed whether there was a correlation between mast cells expressing OSM in bronchoalveolar lavage (BAL) and the severity of sarcoidosis. PATIENTS AND METHODS: Twelve consecutive patients with new diagnosis of sarcoidosis were eligible for the study. All underwent complete lung function tests, angiotensin converting enzyme (ACE), and bronchoscopy that included BAL and biopsies. Cytospins of BAL were prepared. All samples were incubated with the primary antibody rabbit anti-human c-kit, CD117 and stained for total mast cell count. The mouse anti-human Oncostatin M was applied and activated mast cells were counted. Clinical sarcoidosis parameters including ACE and lung functions were correlated with mast cells in BAL, as well as with OSM positive mast cells. RESULTS: FEV1 % was correlated with the percentage of activated mast cells, as well as with the percentage of OSM positive mast cells (r=0.61, p=0.033, 95% CI: 0.06-0.87; r=0.58, p=0.04, 95% CI: 0.015-0.86, respectively). FVC and FEV1/FVC correlated with activated mast cells (r=0.58, p=0.05; r=0.63, p=0.028, respectively). CONCLUSIONS: Direct correlation was found between clinical parameters including lung function tests (FEV1 and FVC) and OSM secretion from mast cells in patients with sarcoidosis. These findings suggest that mast cells and OSM have a role in sarcoidosis. Further studies to confirm these preliminary results are suggested.

Interleukin-6 and soluble intercellular adhesion molecule-1 in acute brain ischaemia.

Inflammation plays a critical role in the pathogenesis of atherothrombosis. Our aim was to examine the association between plasma concentrations of inflammatory biomarkers and severity and outcome of acute brain ischaemia. Plasma samples were collected within 36 h of symptom onset in patients with acute brain ischaemia, and assessed by conventional ELISA kits for concentration of interleukin-6 (IL-6) and soluble intercellular adhesion molecule-1 (sICAM-1). Patients were assessed serially for stroke severity (National Institute of Health stroke scale) and outcome during follow-up (modified Rankin Scale, mRS; and Stroke Impact Scale-16, SIS). Patients (n = 113, 65% men, mean age 64 +/- 12 years) had a mean IL-6 concentrations of 5.1 +/- 5.0 pg/ml and sICAM-1 of 377 +/- 145 ng/ml. IL-6, but not sICAM-1, concentrations were strongly associated with stroke severity (P < 0.01 at all serial assessments). Ln-transformed IL-6 levels (per 1 SD) were associated with disability (mRS > or = 2, OR = 1.7; 95% CI 1.1-3.0) and poor physical function (SIS < or = 85, OR = 1.7; 95% CI 1.0-2.8). Further adjustment for baseline stroke severity, however, eliminated these associations. Our results suggest that high plasma concentrations of the inflammatory biomarker IL-6 but not sICAM-1 are associated with stroke severity and poorer functional outcome. IL-6 does not add, however, additional prognostic information for stroke outcome beyond that conveyed by the stroke severity.

Human mast cells release Interleukin-8 and induce neutrophil chemotaxis on contact with activated T cells.

BACKGROUND: Mast cells have recently been shown to control neutrophil recruitment during T-cell mediated cutaneous DTH reaction in vivo through TNF-alpha and MIP-2, the functional murine analogue of human IL-8. Although the nature of signals transmitted from T cells which activate mast cells has not yet been defined, we hypothesized that a direct cross-talk (i.e. heterotypic adhesion) between these two cell populations exists, as has previously been reported. AIMS: The present study was aimed at gaining insight into the functional role of mast cell-T cell contact in expression and release of IL-8, and its effect on neutrophil chemotaxis. METHODS: The IL-8 gene expression was identified by Affymetrix GeneChip arrays, validated by RT-PCR and the protein measured by ELISA. Chemotaxis was evaluated by using a modified Boyden chamber assay. RESULTS: Mast cells were found to express and release significantly higher concentrations of IL-8 on incubation with membranes obtained from activated, as compared to resting T cells. Supernatants obtained from these activated mast cells induced significant neutrophil chemotaxis that was inhibited by neutralizing mAb to IL-8. CONCLUSIONS: Thus, activated T cells, on heterotypic adhesion to mast cells, deliver the necessary signals for the latter to release cytokines and chemokines necessary for cell migration to sites of antigen challenge, thereby facilitating T-cell mediated inflammatory processes.

Induction of mast cell interactions with blood vessel wall components by direct contact with intact T cells or T cell membranes in vitro.

BACKGROUND: Mast cells exert profound pleiotropic effects on immune cell reactions at inflammatory sites, where they are most likely influenced not only by the extracellular matrix (ECM) and inflammatory mediators but also by the proximity of activated T lymphocytes. We recently reported that activated T cells induce mast cell degranulation with the release of TNF-alpha, and that this activation pathway is mediated by lymphocyte function-associated antigen-1 (LFA-1)/intercellular adhesion molecule-1 (ICAM-1) binding. OBJECTIVE: To determine how this contact between the two cell types can modulate mast cell behaviour in an inflammatory milieu by examining the adhesion of mast cells to endothelial cells and ECM ligands in an integrin-dependent manner. METHODS: Human mast cells (HMC-1) were co-cultured with resting or activated T cells followed by testing their adhesion to endothelial cell and ECM ligands, stromal derived factor-1alpha (SDF-1alpha)-induced migration, and western blotting. RESULTS: Co-culturing HMC-1 with activated, but not with resting T cells resulted in marked stimulation of mast cell adhesion to vascular cell adhesion molecule-1 and ICAM-1 in a very late antigen-4- and LFA-1-dependent fashion. In addition, activated T cells or T cell membranes promoted HMC-1 adhesion to fibronectin (FN) and laminin. This effect was accompanied by the phosphorylation of extracellular regulated kinase and p38, but not of c-Jun N-terminal kinase. Importantly, the adhesive property of mast cells depended exclusively on the direct contact between the two cell types, since neither supernatants from activated T cells nor separation of the two cell populations with a porous membrane affected mast cell adhesion to FN. Furthermore, similar results were obtained when mast cells were incubated with purified membranes from activated T cells. These results suggest that, in addition to stimulating mast cell degranulation, the proximity of activated T lymphocytes to mast cells can mediate the adhesion of mast cell precursors to the endothelial ligands and ECM. Activated T cells also stimulated SDF-1alpha-induced mast cell migration. CONCLUSION: This symbiotic relationship between the two types of immune cells may serve to direct mast cells to specific sites of inflammation where their effector functions are required.

Evidence for altered mast cell proliferation and apoptosis in cutaneous mastocytosis.

BACKGROUND: Mastocytosis presents as a focal or generalized increase of mast cells, particularly in the skin, but also in other organs. Activating mutations of KIT (formerly c-kit), the receptor of the mast cell growth factor stem cell factor (SCF), appear to play a key role in the pathogenesis of sporadic adult onset mastocytosis. However, these mutations are not present in childhood-onset and familial mastocytosis and also fail to explain the heterogeneity of adult-onset disease. Other factors such as prolonged survival of mast cells may therefore participate in causing and modulating the pathological increase of mast cells in mastocytosis. OBJECTIVES: To examine the expression of proliferation and apoptosis markers in the mast cells of cutaneous mastocytosis lesions in order to gain further insight into the pathogenesis of mastocytosis. METHODS: Lesional cutaneous biopsies from eight infants with solitary mastocytomas, five children with multiple mastocytomas, 11 children with generalized urticaria pigmentosa, 12 adults with urticaria pigmentosa, and skin from seven normal controls were used in this study. Serial sections were stained with toluidine blue to quantify mast cell numbers and with antibodies against the proliferation marker Ki67 protein, the tumour suppressor protein p53, and the inhibitor of cyclins and cyclin-dependent kinases p21WAF1/CIP1, using the alkaline phosphatase antialkaline phosphatase technique. The terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labelling (TUNEL) method was used to assess apoptosis. RESULTS: Cutaneous mast cell counts were significantly increased in all patient sections, particularly in childhood lesions, and similarly, a small but significant increase of proliferation was found in the lesional mast cells of all patients. Enhanced mast cell numbers and proliferation was associated with a significant decrease of TUNEL staining, particularly in mastocytomas. p53 expression was highly variable, with an overall significant increase in all patient skin mast cells, whereas p21 expression was barely observed at all. CONCLUSIONS: These findings further support the concept that an imbalance of mast cell proliferation and apoptosis is prevalent in mastocytosis lesions that may account in part for the increased focal mast cell accumulation in this condition.

Rheumatoid neutrophilic dermatitis: an initial dermatological manifestation of seronegative rheumatoid arthritis.

Rheumatoid neutrophilic dermatitis (RND) is an uncommon, but distinctive manifestation of rheumatoid arthritis (RA). We describe the case of a 35-year-old female who developed RND as an early stage of seronegative RA. Clinically, the lesions were presented by erythematous, slightly tender, papules, 5-10 mm in diameter, on the extensor surface of the left arm. The histopathological findings revealed a dense, dermal, mainly neutrophilic infiltrate, with prominent leucocytoclasia, but without any features of vasculitis. There was fibrinoid degeneration of collagen, resembling the collagen changes present in rheumatoid nodules in a miniaturized form. RND can be a reliable, early clinical sign of RA, as seen in our patient. Furthermore, this case demonstrates that RND may be associated not only with seropositive RA, as described in the literature, but also with seronegative RA, never before reported. The histological findings in our case are remarkable because of the fibrinoid collagen degeneration, which is described here for the first time in RND. Thus, RND may, in fact, be the initial phase of a spectrum that begins with a neutrophilic reaction and mild fibrinoid collagen degeneration, and evolves into rheumatoid nodules at the final stage.

Human mast cells release metalloproteinase-9 on contact with activated T cells: juxtacrine regulation by TNF-alpha.

Mast cells, essential effector cells in allergic inflammation, have been found to be activated in T cell-mediated inflammatory processes in accordance with their residence in close physical proximity to T cells. We have recently reported that mast cells release granule-associated mediators and TNF-alpha upon direct contact with activated T cells. This data suggested an unrecognized activation pathway, where mast cells may be activated during T cell-mediated inflammation. Herein, we show that this cell-cell contact results in the release of matrix metalloproteinase (MMP)-9 and the MMP inhibitor tissue inhibitor of metalloproteinase 1 from HMC-1 human mast cells or from mature peripheral blood-derived human mast cells. The expression and release of these mediators, as well as of beta-hexosaminidase and several cytokines, were also induced when mast cells were incubated with cell membranes isolated from activated, but not resting, T cells. Subcellular fractionation revealed that the mature form of MMP-9 cofractionated with histamine and tryptase, indicating its localization within the secretory granules. MMP-9 release was first detected at 6 h and peaked at 22 h of incubation with activated T cell membranes, while TNF-alpha release peaked after only 6 h. Anti-TNF-alpha mAb inhibited the T cell membrane-induced MMP-9 release, indicating a possible autocrine regulation of MMP release by mast cell TNF-alpha. This cascade of events, whereby mast cells are activated by T cells to release cytokines and MMP-9, which are known to be essential for leukocyte extravasation and recruitment to affected sites, points to an important immunoregulatory function of mast cells within the context of T cell-mediated inflammatory processes.

Human mast cell apoptosis is regulated through Bcl-2 and Bcl-XL.

It is well established that human mast cell proliferation and maturation are regulated by kit ligand (stem cell factor). Little is known, however, about how these two processes are negatively regulated and thus, how mast cell number is controlled in normal and pathologic conditions. We therefore first hypothesized that SCF-dependent human mast cells would undergo programmed cell death (apoptosis) on removal of SCF as has been shown for growth factor-dependent rodent mast cells. We then examined whether SCF acts as a survival factor through the regulation of the bcl-2 family of apoptosis-regulatory genes. As hypothesized, elimination of SCF from primary peripheral blood-derived human mast cell cultures resulted in a significant apoptotic process. During apoptosis, down-regulation of the two apoptosis-regulatory proteins Bcl-2 and Bcl-XL was observed. Moreover, a deregulated expression of these two proteins was found in two human mast cell lines which are SCF-independent. Thus, SCF functions as a survival factor by repressing apoptosis of human mast cells through Bcl-2 and Bcl-XL. Deregulated expression of these antiapoptotic proteins may contribute to proliferation and accumulation of mast cells in certain forms of systemic mast cell disorders.

Synaptotagmin regulates mast cell functions.

Synaptotagmin(s) (Syts), are products of a gene family implicated in the control of Ca2+-dependent exocytosis. Mast cells, specialized secretory cells that release mediators of inflammatory and allergic reactions in a process of regulated exocytosis, express Syt homologues and SNAREs (Soluble NSF Attachment proteins Receptors), which together with Syt constitute the core complex which mediates exocytotic vesicle docking and fusion. Rat basophilic leukemia cells (RBL-2H3), a tumor analogue of mucosal mast cells, express the Syt homologues Syt II, Syt III and Syt V Expression of Syt I, the neuronal Ca2+ sensor, in the RBL cells, resulted in its targeting to secretory granules and in prominent potentiation and acceleration of Ca2+-dependent exocytosis. Syt II is localized to an amine-free lysosomal compartment, which is also subjected to regulated exocytosis. Lysosomal exocytosis is negatively regulated by Syt II: overexpression of Syt II inhibited Ca2+-triggered exocytosis of lysosomes, while suppression of Syt II expression markedly potentiated this release. These findings implicate Syt homologues as key regulators of mast cell function.

Lupus-like syndrome with submassive hepatic necrosis associated with hepatitis A.

Hepatitis A is a common self-limited liver disease. However, 15% of patients may have some complications. Autoimmune hepatitis that is triggered by viral hepatitis has been reported. We hereby describe an unrecognized association of hepatitis A with a full blown lupus-like syndrome manifested by the appearance of arthralgia, exudative pleural effusion with the presence of lupus erythematosus cells and autoantibodies. All these findings disappeared after a short course of steroid treatment. The case is presented and the literature is reviewed.

Lymphoid tissues and the immune system in mastocytosis.

The association of mast cells and lymphoid tissues may reflect either regional overproduction of growth factors for mast cells or a predisposition for mast cells at certain sites within the body, particularly the liver, lymph nodes, and spleen. The significant increase in mast cell number associated with mastocytosis is not sufficient to generate a change in either T-cell or B-cell functions, as evaluated by analyzing cytokine phenotype or immunoglobulin production, respectively, nor to expose these patients to infections or allergic diseases. Mast cells in mastocytosis cannot be said with certainty to be "normal" in all respects, however, and the failure to identify an effect of mast cells on either B-cell Ig production or T-cell cytokine profiles cannot be taken as absolute evidence that mast cell products have no influence on lymphocyte function, particularly at the local tissue level.

[Thallium scan and pulmonary carcinoma].

A 70-year-old man was admitted for exacerbation of congestive heart failure. In his assessment thallium scan of the heart was performed. An incidental finding was a focus of absorption in the right lung. The lesion was later diagnosed as adenocarcinoma based on the cytological findings.

Diminished chemokine and cytokine-induced adhesion of CD4+ T cells to extracellular matrix ligands in patients with end-stage renal failure.

BACKGROUND: Cell-mediated immunity is impaired in uremia. Cell-matrix interactions of immune cells such as CD4+ T lymphocytes with extracellular matrix are an important requirement for an intact immune response. The adherence of CD4+ T cells of healthy subjects (normal T cells) to ECM components is inhibited in the presence of uremic serum. Such decreased adhesive capacity is also found in T cells of dialysis patients. Various chemokines and cytokines affect the attachment of CD4+ T cells to ECM. OBJECTIVE: To evaluate chemokine (MIP-1 beta and RANTES) and tumor necrosis factor-alpha-induced adhesion of CD4+ T cells to ECM in a uremic milieu. METHODS: We examined adhesion of normal CD4+ T cells (resting and activated) to intact ECM in response to soluble or bound chemokines (MIP-1 beta and RANTES) and to TNF-alpha following incubation in uremic versus normal serum. Thereafter, we evaluated the adhesion of resting CD4+ T cells from dialysis patients in a similar fashion and compared it to that obtained from a healthy control group. RESULTS: Addition of uremic serum diminished soluble and anchored chemokine-induced attachment of normal resting and activated CD4+ T cells to ECM compared to a normal milieu (a peak response of 10-11% vs. 24-29% for soluble chemokines, P < 0.001; 12-13% vs. 37-39% for bound chemokines on resting cells, P < 0.01; and 18-20% vs. 45-47% for bound chemokines on activated cells, P < 0.02). The same pattern of response was noted following stimulation with immobilized TNF-alpha (7 vs. 12% for resting cells, P < 0.05; 17 vs. 51% for activated cells, P < 0.01). Adherence of dialysis patients' cells to ECM following stimulation with both bound chemokines was reduced compared to control T cells (15-17% vs. 25-32%, P < 0.0000). In contrast, adherence following stimulation by TNF-alpha was of equal magnitude. CONCLUSIONS: Abnormal adhesive capacity of T lymphocytes to ECM in uremia may, in part, be related to a diminished response to MIP-1 beta, RANTES and TNF-alpha. However, whereas reduced adhesion to chemokines was present in both normal CD4+ T cells in a uremic environment and in dialysis patients' T cells, TNF-alpha-induced adhesion was found to be inhibited only in normal cells in a uremic milieu.

Mast cells in innate immunity.

Mast cells are known to be the main effector cells in the elicitation of the IgE-mediated allergic response. The specific location of mast cells within tissues that interface the external environment, and the extent of their functional capacity, including the ability to phagocytose and to produce and secrete a wide spectrum of mediators, have led investigators to propose a potential role for mast cells in innate immune responses. Certain microorganisms have been found to interact either directly or indirectly with mast cells. This interaction results in mast cell activation and mediator release which elicit an inflammatory response or direct killing leading to bacterial clearance. The in vivo relevance of these in vitro observations has been demonstrated by the use of complement-deficient and/or mast cell-deficient and mast cell-reconstituted mice. In thus has been shown that both C3 and mast cell- and tumor necrosis factor-alpha-dependent recruitment of circulating leukocytes with bactericidal properties are crucial to a full response in certain models of acute infection. Modulation of mast cell numbers in vivo was also found to affect the host response against bacterial infection. Thus, mast cells do have a role in innate immunity in defined animal models of bacterial infection. Whether mast cells participate in innate immune responses in the protection of the human host against bacteria remains to be determined.