Comparative aspects of mast cell heterogeneity in different species and sites

Mast cell interleukin-10 drives localized tolerance in chronic bladder infection

The lower urinary tract's virtually inevitable exposure to external microbial pathogens warrants efficient tissue-specialized defenses to maintain sterility. The observation that the bladder can become chronically infected in combination with clinical observations that antibody responses after bladder infections are not detectable suggest defects in the formation of adaptive immunity and immunological memory. We have identified a broadly immunosuppressive transcriptional program specific to the bladder, but not the kidney, during infection of the urinary tract that is dependent on tissue-resident mast cells (MCs). This involves localized production of interleukin-10 and results in suppressed humoral and cell-mediated responses and bacterial persistence. Therefore, in addition to the previously described role of MCs orchestrating the early innate immunity during bladder infection, they subsequently play a tissue-specific immunosuppressive role. These findings may explain the prevalent recurrence of bladder infections and suggest the bladder as a site exhibiting an intrinsic degree of MC-maintained immune privilege.

Mast cell regulation of the immune response

Mast cells are well known as principle effector cells of type I hypersensitivity responses. Beyond this role in allergic disease, these cells are now appreciated as playing an important role in many inflammatory conditions. This review summarizes the support for mast cell involvement in resisting bacterial infection, exacerbating autoimmunity and atherosclerosis, and promoting cancer progression. A commonality in these conditions is the ability of mast cells to elicit migration of many cell types, often through the production of inflammatory cytokines such as tumor necrosis factor. However, recent data also demonstrates that mast cells can suppress the immune response through interleukin-10 production. The data encourage those working in this field to expand their view of how mast cells contribute to immune homeostasis.

Differential corticosterone responses to stress in the lung in two strains of Flinders rats

BACKGROUND

Acute stress affects a variety of organs and cellular systems. These include the hypothalamic-pituitary-adrenal (HPA) axis, corticotropin-releasing factor (CRF), mast cells and nerves. Flinders-sensitive (FSL) rat strains have hypercholinergic responses and are more sensitive than Flinders-resistant rats (FRL) to anaphylaxis.

OBJECTIVE

To investigate the effects of acute water avoidance stress (1 h) on FSL and FRL tracheal epithelial tissue.

METHODS

We measured short circuit current (I(sc)) as a measure of tracheal response, and the effect of substance P (SP) on tracheal epithelium in Ussing chambers. Electron microscopy was performed to assess mast cell activation.

RESULTS

Both strains showed increased I(sc) responses to stress, inhibited by prior injection of the CRF receptor 1 and 2 antagonist, alpha-helical CRF-(9-41). No increases in conductance were seen. Stress responses were accompanied by electron microscopic morphologic evidence for mast cell degranulation, which was not completely inhibited by alpha-helical CRF-(9-41) pre-treatment. Stress primed the epithelium for an enhanced response to SP in FSL, but this again was not inhibited by alpha-helical CRF-(9-41). FRL had 2.5 times the corticosterone response of FSL.

CONCLUSION

Acute stress affects the tracheal epithelium, not accompanied by changes in ion permeability, but associated with mast cell degranulation. Because blunted HPA axis responses are associated with vulnerability to inflammation, this may partially explain the findings. These stress effects on the lung have a genetic basis associated with relative corticosterone responses, are complex and only in part mediated by CRF.

Mast cells and nerves tickle in the tummy: implications for inflammatory bowel disease and irritable bowel syndrome

Mast cells are well known as versatile cells capable of releasing and producing a variety of inflammatory mediators upon activation and are often found in close proximity of neurons. In addition, inflammation leads to local activation of neurons resulting in the release neuropeptides, which also play an important immune modulatory role by stimulation of immune cells. In intestinal disorders like inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS), the number of mast cells is known to be much higher than in the normal intestine. Moreover, both these disorders are also reported to be associated with alterations in neuropeptide content and in neural innervation. Mutual association between mast cells and enteric nerves has been demonstrated to be increased in pathophysiological conditions and contribute to spreading and amplification of the response in IBD and IBS. In this review the focus lies on studies appointed to the direct interaction between mast cells and nerves in IBD, IBS, and animal models for these disorders so far.

Small strongyle infection: consequences of larvicidal treatment of horses with fenbendazole and moxidectin

The study was undertaken to evaluate adverse effects of larvicidal treatment in horses naturally infected with cyathostomins. Out of 24 ponies kept on pasture, four animals were housed in September and anthelmintically cured to serve as worm-free controls (group C-0). The others were housed in December. Eight animals each were treated 8 weeks later with 5 x 7.5mg/kg fenbendazole (FBZ) or 1 x 0.4 mg/kg moxidectin (MOX). Four animals remained untreated (group C-i). Two, 4, 6 and 14 days after the end of treatment two animals of each of the treated groups were necropsied together with group C-0 and C-i animals. Infected animals before treatment showed weight loss, eosinophilia, increased plasma protein and globulin contents. Treatment was followed by weight gain and temporal plasma protein and globulin increase. Proportions of CD4+ and CD8+ T lymphocytes in the peripheral blood did not differ between the groups before treatment but dropped significantly temporally after FBZ treatment. Group C-0 was worm-free at necropsy. Group C-i animals contained variable numbers of luminal and tissue cyathostomins. Histological sections showed larval stages in the lamina propria und submucosa surrounded by macrophages. Either treatment was effective against luminal parasites and reduced the number of larvae in the bowel wall beginning 4-6 days after FBZ and 6-14 days after MOX treatment. Histologically, as a first reaction after FBZ application T lymphocytes accumulated around morphologically intact L4 in the submucosa. Subsequently T lymphocytes associated with eosinophils infiltrated the submucosa. Parasites became enclosed by granulomas with eosinophils adhering to and invading the larvae which started to disintegrate on day 4. Later on, particularly on day 14 inflammation extended into the mucosa and was frequently associated with ulcerations. Third stage larvae in general and L4 in the lamina propria, however, seemed not to be affected until day 14 and even then, parasites did usually not generate extensive inflammation. After MOX treatment severe morphologically detectable alterations of tissue larvae could not be observed earlier than day 14. Different from FBZ treatment, larvae disintegrated and were obviously resorbed without causing severe inflammation in the gut wall. In conclusion treatment with either drug was efficacious against tissue larvae of cyathostomins but there may be different clinical consequences: in contrast to MOX effects, killing of larvae due to FBZ was associated with severe tissue damage, which clinically may correspond to reactions caused by synchronous mass emergence of fourth stage larvae, i.e., may mimic larval cyathostominosis.

Mast cells as "tunable" effector and immunoregulatory cells: recent advances

This review focuses on recent progress in our understanding of how mast cells can contribute to the initiation, development, expression, and regulation of acquired immune responses, both those associated with IgE and those that are apparently expressed independently of this class of Ig. We emphasize findings derived from in vivo studies in mice, particularly those employing genetic approaches to influence mast cell numbers and/or to alter or delete components of pathways that can regulate mast cell development, signaling, or function. We advance the hypothesis that mast cells not only can function as proinflammatory effector cells and drivers of tissue remodeling in established acquired immune responses, but also may contribute to the initiation and regulation of such responses. That is, we propose that mast cells can also function as immunoregulatory cells. Finally, we show that the notion that mast cells have primarily two functional configurations, off (or resting) or on (or activated for extensive mediator release), markedly oversimplifies reality. Instead, we propose that mast cells are "tunable," by both genetic and environmental factors, such that, depending on the circumstances, the cell can be positioned phenotypically to express a wide spectrum of variation in the types, kinetics, and/or magnitude of its secretory functions.

Mast-cell responses to pathogens

Mast cells have mainly been studied in the setting of allergic disease, but the importance of mast cells for host defence against several pathogens has now been well established. The location of mast cells, which are found closely associated with blood vessels, allows them to have a crucial sentinel role in host defence. The mast cell has a unique 'armamentarium' of receptor systems and mediators for responding to pathogen-associated signals. Studies of this intriguing immune-effector cell provide important insights into the complex mechanisms by which appropriate innate and acquired immune responses are initiated.

Immunologically induced histamine release from rat peritoneal mast cells is enhanced by low levels of substance P

Although direct activation of mast cells by high concentrations (>10(-6) M) of substance P is well established, the effect of sub-micromolar concentrations of the neuropeptide on mast cell activation has not been reported. We hence investigated if substance P would modulate immunologic activation of mast cells by studying the effect of the neuropeptide on anti-rat immunologlobulin E antibody (anti-IgE)-induced histamine release from purified rat peritoneal mast cells. We observed that substance P could dose-dependently potentiate anti-IgE-induced histamine release from rat peritoneal mast cells at concentrations (3x10(-9) M to 3x10(-7) M) which alone induced insignificant or low level of histamine release. While the potentiating effect of substance P was not suppressed by any of the non-peptide tachykinin receptor antagonists CP99994 ((2S,3S)-3-(2-methoxybenzylamino)-2-phenylpiperidine), SR48968 ((S)-N-methyl-N-(4-acetylamino-4-phenylpiperidino)-2-(3,4-dichlorophenyl) butyl-benzamide) and SR142801 ((S)-(N)-(1-[3-(1-benzoyl-3(3,4-dichlorophenyl)piperidine-3-yl)propyl]-4-phenylpiperidin-4-yl)-N-methyl-acetamide), it was mimicked by compound 48/80 and suppressed by benzalkonium chloride. Hence, substance P enhanced anti-IgE-induced histamine release through a similar receptor-independent mechanism as the direct mast cell activating action of polybasic compounds. Since high concentrations of substance P required for directly activating mast cells may not be achievable physiologically, the enhancing actions of the neuropeptide on the immunologic activation of mast cells may be more clinically relevant in the pathogenesis of various inflammatory conditions.

Influence of IgE-mediated activation of cultured human mast cells on proliferation and type I collagen production by human dermal fibroblasts

BACKGROUND

Mast cells have been suggested to be involved in fibrotic conditions, but it still remains unknown whether IgE-mediated activation of human mast cells promotes fibrogenesis by human fibroblasts.

OBJECTIVE

The purpose of this study was to determine whether IgE-mediated activation of cultured human mast cells can promote fibrogenesis by cultured human dermal fibroblasts.

METHODS

Mast cells derived from human umbilical cord blood cells were incubated with IgE and then activated by anti-IgE, and histamine release was measured. IgE-sensitized mast cells were cocultured with fibroblasts from normal dermis and activated with anti-IgE to induce histamine release, after which proliferation and type I collagen synthesis by the fibroblasts were determined.

RESULTS

Coculture of subconfluent human dermal fibroblasts with IgE-sensitized mast cells did not affect fibroblast proliferation. However, fibroblast proliferation was increased by activated mast cells, and a significant increase was observed in the presence of 10(5) or 3 x 10(5) mast cells/mL. The promotion of fibroblast proliferation by mast cells (3 x 10(5)/mL) was partly inhibited by ketotifen at a concentration that significantly reduced histamine release from mast cells. On the other hand, IgE-mediated activation of mast cells did not increase type I collagen production by confluent human dermal fibroblasts.

CONCLUSION

IgE-mediated activation of cultured human mast cells could increase the proliferation of human dermal fibroblasts, but did not promote type I collagen production by the fibroblasts under the conditions tested.

Carnoy's fixative reduces the number of chymase-positive cells in immunocytochemical staining of cord-blood-derived human cultured mast cells

KleinJan et al. (Allergy 1996;51:614-20) reported that Carnoy's fixative reduced the number of chymase-positive mast cells in the nasal mucosa. Therefore, in the present study, we investigated whether Carnoy's fixative reduces the number of chymase-positive cells from cord-blood-derived human cultured mast cells when compared with other types of fixatives. Human mast cells were obtained by culturing cord-blood-derived CD34-positive cells in the presence of stem cell factor and interleukin-6. Staining procedures of the cells in fixation with Carnoy's fixative and with other fixatives gave no differences among the number of tryptase-positive cells, whereas fixation with Carnoy's fixative for 15 min gave a significant decrease in the number of chymase-positive cells compared with acetone for 10 min. The number of chymase-positive cells decreased in a time-dependent manner under fixation with Carnoy's fixative, indicating that Carnoy's fixative had a negative effect on the number of chymase-positive cells from cord-blood-derived human cultured mast cells.

Phase-contrast microscopic studies using cinematographic techniques and scanning electron microscopy on IgE-mediated degranulation of cultured human mast cells

BACKGROUND

Isolating human mast cells is a laborious procedure. Recently, cultured human mast cells raised from umbilical cord blood cells have become available. It is necessary to investigate whether IgE-mediated activation of these cells is mediated by exocytosis.

OBJECTIVE

To verify IgE-mediated activation of these cultured human mast cells morphologically.

METHODS

The mast cells were raised from human umbilical cord blood cells in the presence of stem cell factor and interleukin-6. IgE-sensitized cultured human mast cells were activated by anti-IgE, and morphological changes of the cells were examined under phase-contrast microscopy using cinematographic techniques and scanning electron microscopy. Histamine release from the cells was measured with high-performance liquid chromatography.

RESULTS

Under the condition in which a significant histamine release was observed from the mast cells, phase-contrast microscopy showed that the cultured human mast cells became swollen and extruded granules. Scanning electron microscopy disclosed the extrusion of smooth and round bodies from pores formed on the activated mast cell surface.

CONCLUSION

IgE-mediated histamine release from cultured human mast cells is accompanied by exocytosis morphologically, indicating that cultured human mast cells will help in studying the functional properties of human mast cells.

Mast cell-derived histamine and tumour necrosis factor: differences between SJL/J and BALB/c inbred strains of mice

Mast cells cultured from bone marrow of BALB/c and SJL/J inbred strains of mice using IL-3 showed distinct patterns of growth and marked differences in their content of TNF-alpha and histamine. Mast cells derived from SJL/J mice grew and matured at a faster rate than those from BALB/c bone marrow. SJL/J mast cells were found to contain more than twice the amount of histamine and TNF-alpha in their granules than BALB/c-derived cells. In addition, when triggered by anti-DNP IgE antibody and specific antigen (DNP-albumin), mast cells derived from SJL/J mice released more histamine and TNF-alpha than mast cells derived from BALB/c mice. These results confirm previous observations regarding a genetic basis for mouse strain differences in mast cell growth rates, and extend previous observations to document differences in mast cell mediator contents. These results are consistent with the concept that genetically controlled differences in the numbers of central nervous system (CNS)-associated mast cells and their vasogenic mediators may play an important role in modulating oedema and inflammation in CNS trauma and diseases in mice.

Mast cells in normal and pathological specimens of the equine lung

In lungs from 22 horses, the number and type of mast cells in histologically normal specimens were compared with those in specimens with various histological lesions. Tissues fixed in Carnoy's solution were superior to those fixed in formalin for the identification of mast cells. Fixation of lung specimens from eight horses in Carnoy's solution and formalin allowed the identification of two subpopulations of mast cells: formalin-sensitive, which predominated and formalin-resistant. Specimens with mild chronic tracheitis and mild and moderate chronic bronchitis generally had slight increases in mast cell numbers in comparison to histologically normal specimens. An increase in mast cell numbers was also observed around small and large bronchioles with mild, moderate and severe bronchiolitis and in fibrosed pulmonary pleurae in comparison to specimens with no histological lesions. The most striking increase in mast cell numbers was seen in fibrosed alveolar septa; there were approximately four times as many mast cells in these specimens as in specimens with normal histology.

The jejunal secretion of histamine is increased in active Crohn's disease

Previous studies of mast-cell density and histamine content in biopsy specimens in patients with Crohn's disease have yielded conflicting results. In this in vivo study we have measured the jejunal secretion rate of histamine in patients with Crohn's disease (n = 15) of the terminal small bowel and in healthy controls (n = 24). The secretion studies were performed using a recently developed segmental jejunal perfusion system with a two-balloon, six-channel small tube. The histamine secretion rate was 152 +/- 29 (SEM) ng/cm small intestine per h in patients with Crohn's disease, which meant a significant increase (p less than 0.01) compared with the secretion rate in controls (71 +/- 11 ng/cm per h). Moreover, the secretion of histamine was related to the disease activity. Patients with active disease (n = 8) (i.e., Crohn's disease activity index greater than 150) had a mean histamine secretion rate of 193 +/- 47 ng/cm per h, while patients with inactive disease (Crohn's disease activity index less than 150) had a secretion rate not significantly increased compared with controls (105 +/- 24 ng/cm per h). The present data indicate increased mast-cell involvement of the small intestine in active Crohn's disease of the distal ileum. This finding might reflect the systemic nature of the disease process.

Study of the effect of some neuropeptides and endogenous opioid peptides on in vitro histamine release from human lung mast cells and peripheral blood basophils

In the present study we investigated the effect of substance P, bombesin, beta lipotropin, alpha and gamma endorphins, and metionin and leucin enkephalins on in vitro histamine release from partially purified human lung mast cells and peripheral blood basophils. In the concentration range of 10-100 microM, these neuropeptides and endogenous opioid peptides neither elicited a significant histamine secretions from human lung mast cells and blood basophils, nor influenced the anti-IgE-induced histamine release. These data indicate that human lung mast cells and blood basophils are resistant to the activity of substance P, bombesin, beta lipotropin, alpha and gamma endorphins, and metionin and leucin enkephalins, and confirm the functional heterogeneity of mast cells, depending on the species and the tissue origin.

Enhanced bronchoalveolar lavage mast cells histamine releasability in allergic dogs with and without airway hyperresponsiveness

To determine if mast cells from the airway lumen of Basenji-greyhound (BG) dogs differ functionally from mast cells of control dogs, we compared spontaneous release and A 23187-induced and C5-induced histamine release from bronchoalveolar lavage (BAL) fluid of 14 BG and five allergic and five nonallergic control dogs. No dog received antigen, agonist, or therapeutic aerosols for 4 weeks before BAL. The fluid recovered was centrifuged, and the number of mast cells was quantitated. Aliquots containing equal numbers of mast cells were incubated with A 23187 or C5 for 30 minutes, and histamine release was measured by an automated fluorometric method. Spontaneous release, A 23187-induced release, C5-induced release, and total histamine content per mast cell were calculated. The total amount of histamine per mast cell was not significantly different in BGs and allergic and nonallergic control dogs. Mast cells obtained by BAL released histamine to A 23187 and C5 in a dose-related manner. Spontaneous histamine release and A 23187-induced histamine release was significantly greater in BGs and allergic control dogs compared to nonallergic control dogs. C5-induced histamine release was significantly greater in BGs than in allergic as well as nonallergic control dogs. These data suggest that BAL mast cell histamine releasability must be defined with respect to each stimulus and that mast cells obtained from BAL from control dogs differ with respect to histamine releasability from mast cells of allergic dogs with and without airway hyperresponsiveness. This study suggests that mast cells obtained from BAL can be used to study mast cell function in the control and the allergic state.

Separation and Characterization of Leukocytes from the Intestine

This chapter discusses the methods for the separation and characterization of leukocytes from the intestine. Intestinal immune mechanisms must be studied directly and incorporated into models based on the observations made using intestinal cells and not just systemic cells. Numerous reports in the literature compare and contrast mucosal and systemic responses; however, despite their tissue-specific variations, the different tissues do interact. The procedures used to isolate cells from gut-associated lymphoid tissue (GALT) are traumatic or include enzyme digestion. A technique should be selected that is efficient yet gentle enough to provide viable and functional cells. Moreover, the cells contaminating leukocyte preparations can affect the functional assays. This necessitates that positive controls are put through the procedure or even added to intestinal pieces before isolation. If these cells demonstrate a positive response following this handling, then one is more confident of negative results observed in the isolated intestinal cells.