In situ detection of the mast cell proteases chymase and tryptase in human lung tissue using light and electron microscopy

Initial investigation of molecular phenotypes of airway mast cells and cytokine profiles in equine asthma

Equine asthma is a naturally occurring lung disease characterized by chronic, partially reversible airway obstruction, pulmonary remodeling, and lower airway inflammation. Asthma is currently divided into two major groups, mild to moderate asthma (mEA) and severe asthma (sEA), but further subtyping by phenotype (i.e., clinical presentation) and/or endotype (i.e., cellular mechanisms) may be warranted. For this study, we were interested in further investigation of cellular and inflammatory characteristics of EA, including airway mast cells. The purpose of this study was to: (1) compare mast cell protease mRNA expression between healthy and asthmatic horses, (2) analyze the cytokine profile present in BALF of currently defined equine asthma groups, and (3) use these data to evaluate potential biomarkers of defined asthma groups. We hypothesized that there would be significant differences in the cellular mast cell phenotypes (i.e., mucosal vs. connective tissue) and cytokine profiles in the BALF of asthmatic vs. healthy horses and across asthma groups. We assert these characteristics may inform additional subtypes of equine asthma. Adult horses were recruited from the institution's teaching herd and clinical caseload. Mast cell protease gene expression of the BALF cellular component and multiplex bead immunoassay for cytokine concentrations in the BALF supernatant were investigated. Airway mast cells primarily expressed tryptase, with low levels of chymase. No significant changes in protease expression were detected across groups. Horses with severe asthma had increased TNF-α, CXCL-8, and IFN-γ concentrations in BALF supernatant. Multidimensional analysis demonstrated healthy and mEA horses have overlapping characteristics, with sEA separating from the other groups. This difference was primarily due to BALF neutrophil and lymphocyte concentrations. These study results further inform understanding of EA immunopathology, and future studies designed to investigate asthma phenotypes and endotypes. Ultimately, a better understanding of these groups could help identify novel therapeutic strategies.

Modern Imaging Technologies of Mast Cells for Biology and Medicine (Review)

Mast cells play an important role in the body defense against allergens, pathogens, and parasites by participating in inflammation development. However, there is evidence for their contributing to the pathogenesis of a number of atopic, autoimmune, as well as cardiovascular, oncologic, neurologic, and other diseases (allergy, asthma, eczema, rhinitis, anaphylaxis, mastocytosis, multiple sclerosis, rheumatoid arthritis, inflammatory gastrointestinal and pulmonary diseases, migraine, etc.). The diagnosis of many diseases and the study of mast cell functions in health and disease require their identification; so, the knowledge on adequate imaging techniques for mast cells in humans and different species of animals is of particular importance. The present review summarizes the data on major methods of mast cell imaging: enzyme histochemistry, immunohistochemistry, as well as histochemistry using histological stains. The main histological stains bind to heparin and other acidic mucopolysaccharides contained in mast cells and stain them metachromatically. Among these are toluidine blue, methylene blue (including that contained in May-Grünwald-Giemsa stain), thionin, pinacyanol, and others. Safranin and fluorescent dyes: berberine and avidin - also bind to heparin. Longer staining with histological dyes or alcian blue staining is needed to label mucosal and immature mast cells. Advanced techniques - enzyme histochemistry and especially immunohistochemistry - enable to detect mast cells high-selectively using a reaction to tryptases and chymases (specific proteases of these cells). In the immunohistochemical study of tryptases and chymases, species-specific differences in the distribution of the proteases in mast cells of humans and animals should be taken into account for their adequate detection. The immunohistochemical reaction to immunoglobulin E receptor (FcεRI) and c-kit receptor is not specific to mast cells, although the latter is important to demonstrate their proliferation in normal and malignant growth. Correct fixation of biological material is also discussed in the review as it is of great significance for histochemical and immunohistochemical mast cell detection. Fluorescent methods of immunohistochemistry and a multimarker analysis in combination with confocal microscopy are reported to be new technological approaches currently used to study various mast cell populations.

Fluorogenic probes for disease-relevant enzymes

Traditional biochemical methods for enzyme detection are mainly based on antibody-based immunoassays, which lack the ability to monitor the spatiotemporal distribution and, in particular, the in situ activity of enzymes in live cells and in vivo. In this review, we comprehensively summarize recent progress that has been made in the development of small-molecule as well as material-based fluorogenic probes for sensitive detection of the activities of enzymes that are related to a number of human diseases. The principles utilized to design these probes as well as their applications are reviewed. Specific attention is given to fluorogenic probes that have been developed for analysis of the activities of enzymes including oxidases and reductases, those that act on biomacromolecules including DNAs, proteins/peptides/amino acids, carbohydrates and lipids, and those that are responsible for translational modifications. We envision that this review will serve as an ideal reference for practitioners as well as beginners in relevant research fields.

Mast cells and cancer

Mast cells (MCs) are a potent proangiogenic factor in tumors, they product several pro-angiogenic factors such as fibroblast growth factor 2 (FGF-2), vascular epithelial growth factor (VEGF), tryptase and chymase. Tryptase is a serine protease classified as α-tryptase and β-tryptase, both produced by MCs. Tryptase degrades the tissues, playing an important role in angiogenesis and in the development of metastases. Serum tryptase increases with age, with increased damage to cells and risk of developing a malignancy and it could be considered the expression of a fundamental role of MCs in tumor growth or, on the contrary, in the antitumor response. Many biomarkers have been developed in clinical practice for improving diagnosis and prognosis of some neoplasms. Elevated tryptase levels are found in subgroups of patients with haematologic and solid cancers. In the current review, we want to update the perspectives of tryptase as a potential biomarker in daily practice in different neoplasms.

Intratumoral and Peritumoral Mast Cells in Malignant Melanoma: An Immunohistochemical Study

BACKGROUND

The aim of the current study was to determine mast cell infiltration in malignant melanoma by immunohistochemistry method and its relationship with some of the cancer prognostic factors, including age, sex, and depth of the tumor.

MATERIALS AND METHODS

In this retrospective analytic cross-sectional study, paraffin-embedded tissue blocks of patients with cutaneous malignant melanoma who had undergone excisional biopsy were studied. Mast cells count in studied cases in different stages of the tumor depth was evaluated by mast cell tryptase immunohistochemistry method. Mast cells infiltration was evaluated both inside the tumor and peritumoral area. Tumor infiltrating lymphocytes (TILs) was also determined. Distribution of intratumoral and peritumoral mast cells and TILs was compared in different stages tof tumor depth.

RESULTS

In this study, 51 cases with melanoma were studied. Mean ± standard deviation (SD) of intratumoral mast cells in stages 1, 2, and 3 was 9.4 ± 4.2, 10.8 ± 5.1, and 2.1 ± 2.3, respectively (P = 0.000). Mean ± SD of peritumoral mast cells in stages 1, 2 and 3 was 13.4 ± 2.4, 16.6 ± 2.4 and 8.2 ± 4.6, respectively (P = 0.000). There was a significant direct relationship between depth of the tumor and TIL (P = 0.000) and distribution of intratumoral (P = 0.000) and peritumoral mast cells (P = 0.000).

CONCLUSION

Lower distribution of intratumoral and peritumoral mast cells and TILs in higher stages of tumor depth in malignant melanoma suggests a possible inhibitory effect of infiltrating mast cells and lymphocytes on the progression of this tumor.

Specific Light-Up Probe with Aggregation-Induced Emission for Facile Detection of Chymase

Human chymases are important proteases abundant in mast cell granules. The elevated level of chymases and other serine proteases is closely related to inflammatory and immunoregulatory functions. Monitoring of the chymase level is very important, however, the existing methods remain limited and insufficient. In this work, a light-up probe of TPETH-2(CFTERD3) (where CFTERD is Cys-Phe-Thr-Glu-Arg-Asp) was developed for chymase detection. The probe has low fluorescent signal in aqueous media, but its solubility can be changed after hydrolysis by chymase, giving significant fluorescence turn-on with a high signal-to-noise (S/N) ratio. The probe has excellent selectivity to chymase compared to other proteins and can effectively differentiate chymase from other enzymes (e.g., chymotrypsin and trypsin) in the same family (E.C. 3.4.21). The detection limit is calculated to be 0.1 ng/mL in PBS buffer with a linear range of 0-9.0 ng/mL. A comparison study using TPETH-2(CFTERD2) as the probe reveals the importance of molecular design in realizing the high S/N ratio. TPETH-2(CFTERD3) thus represents a simple turn-on probe for chymase detection, with real-time and direct readout and also excellent sensitivity and selectivity.

The two faces of mast cells in food allergy and allergic asthma: the possible concept of Yin Yang

The purpose of this review is to discuss the role of mast cells in allergic inflammation. We have focused on inflammation associated with allergic asthma and food allergy. Mast cells are 'first line of defense' innate/adaptive immune cells and are widely distributed in tissues in surfaces exposed to the environment. Especially in allergic settings mast cells are extensively studied, as they can be activated to release a wide range of mediators by allergen-IgE specific triggers. In addition, in allergic inflammation mast cells can also be activated non-allergic triggers. Recent studies revealed that mast cells, besides the classical role of pro-inflammatory effector cell, have also emerged as modulators of allergic sensitization and down-regulators of allergic inflammation. Therefore, mast cells can be regarded as 'Ying Yan' modulators in allergic responses in intestinal tract and airways. This article is part of a Special Issue entitled: Mast Cells in Inflammation.

Mast cell phenotype, location, and activation in severe asthma. Data from the Severe Asthma Research Program

RATIONALE

Severe asthma (SA) remains poorly understood. Mast cells (MC) are implicated in asthma pathogenesis, but it remains unknown how their phenotype, location, and activation relate to asthma severity.

OBJECTIVES

To compare MC-related markers measured in bronchoscopically obtained samples with clinically relevant parameters between normal subjects and subjects with asthma to clarify their pathobiologic importance.

METHODS

Endobronchial biopsies, epithelial brushings, and bronchoalveolar lavage were obtained from subjects with asthma and normal subjects from the Severe Asthma Research Program (N = 199). Tryptase, chymase, and carboxypeptidase A (CPA)3 were used to identify total MC (MC(Tot)) and the MC(TC) subset (MCs positive for both tryptase and chymase) using immunostaining and quantitative real-time polymerase chain reaction. Lavage was analyzed for tryptase and prostaglandin D2 (PGD2) by ELISA.

MEASUREMENTS AND MAIN RESULTS

Submucosal MC(Tot) (tryptase-positive by immunostaining) numbers were highest in "mild asthma/no inhaled corticosteroid (ICS) therapy" subjects and decreased with greater asthma severity (P = 0.002). In contrast, MC(TC) (chymase-positive by immunostaining) were the predominant (MC(TC)/MC(Tot) > 50%) MC phenotype in SA (overall P = 0.005). Epithelial MC(Tot) were also highest in mild asthma/no ICS, but were not lower in SA. Instead, they persisted and were predominantly MC(TC). Epithelial CPA3 and tryptase mRNA supported the immunostaining data (overall P = 0.008 and P = 0.02, respectively). Lavage PGD2 was higher in SA than in other steroid-treated groups (overall P = 0.02), whereas tryptase did not differentiate the groups. In statistical models, PGD2 and MC(TC)/MC(Tot) predicted SA.

CONCLUSIONS

Severe asthma is associated with a predominance of MC(TC) in the airway submucosa and epithelium. Activation of those MC(TC) may contribute to the increases in PGD2 levels. The data suggest an altered and active MC population contributes to SA pathology.

[A cyclooxygenase-2 selective inhibitor worsens respiratory function and enhances mast cell activity in ovalbumin-sensitized mice]

BACKGROUND

Cyclooxygenase (COX)-2 activity has been said to have a protective effect in asthmatic patients as a result of prostaglandin E(2) production. In order to elucidate the mechanisms involved, we evaluated the impact of selective inhibition of COX-2 with rofecoxib during ovalbumin challenge, assessing mast cell activity and airway response in a murine model of asthma.

MATERIAL AND METHODS

Mice were sensitized to ovalbumin (10 microg injected intraperitoneally) and further challenged with 0.5% intranasal ovalbumin. Half the sensitized animals were treated orally with rofecoxib (15 mg/kg/d during the challenge phase). Lung function was measured by whole body plethysmography before and after exposure to ovalbumin. The severity of airway inflammation was evaluated by means of a scoring system. Finally, the serum level of mouse mast cell protease-1 was determined as an indicator of mucosal mast cell activity.

RESULTS

Sensitized mice treated with rofecoxib exhibited 2.4-fold greater airway hyperresponsiveness than did vehicle-treated mice at a methacholine concentration of 100mg/ml. A clear trend toward worsening airway inflammation in the presence of rofecoxib was observed, although the difference between rofecoxib-treated and vehicle-treated animals was not significant. These changes were accompanied by a significant increase in mucosal mast cell activity.

CONCLUSIONS

Selective pharmacological inhibition of COX-2 during the challenge phase worsens airway function in the ovalbumin -induced murine model of acute asthma. We suggest that this effect might be at least partially explained by the increase in airway mast cell activity.

Organic dust exposure increases mast cell tryptase in bronchoalveolar lavage fluid and airway epithelium of heaves horses

BACKGROUND

Mast cell degranulation is believed to act as a key event in initiating and maintaining airway response to allergen challenge in human asthma. It is hypothesized that the mast cell may play a similar role in equine heaves, which shares many similarities with occupational dust-induced asthma.

OBJECTIVE

The aim of this study was to quantify the mast cell proteinase tryptase in bronchoalveolar lavage fluid (BALF) from control and heaves-susceptible horses and to investigate tryptase mRNA and protein expression in pulmonary mast cells.

METHODS

Equine BALF tryptase concentrations were determined by ELISA from control and heaves-susceptible horses pre and post 24 h hay/straw challenge (HSC). Tryptase mRNA and protein expression were investigated by quantitative PCR and immunohistochemistry in bronchial and bronchiolar tissue samples of control and heaves-susceptible horses.

RESULTS

Both control and heaves-susceptible horses had significantly increased BALF tryptase concentrations following HSC (P=0.003 and 0.034, respectively). Increased numbers of tryptase-expressing intra-epithelial mast cells were demonstrated in heaves horses, but not controls, following challenge (P=0.02). Bronchiolar tissue from heaves horses removed from challenge contained significantly lower tryptase transcripts than that from control horses (P=0.02).

CONCLUSION

Mast cell degranulation and tryptase release into the airways occur following HSC of control and heaves-susceptible horses. The greater number of mast cells available in the bronchiolar epithelium of heaves horses may be clinically significant in the pulmonary inflammatory response of heaves.

Histamine release from human buffy coat-derived mast cells

Mast cells are unique immune cells that release a spectrum of chemical mediators contributing to the inflammatory symptoms of allergic disorders. Although mast cell biology has been extensively studied in the rodents, research on human mast cells is hampered by the lack of a convenient preparation source. This problem has now been addressed by culturing human mast cells from CD34(+) progenitors. We have recently discovered that human buffy coat preparations from local blood banks are an abundant and convenient source of progenitors for culturing mature mast cells which express functional high affinity IgE receptors and contain histamine and tryptase in their granules. In the current study, we further characterize these buffy coat-derived mast cells by studying their responses to common mast cell secretagogues and stabilizers. Mature human mast cells were obtained by culturing isolated progenitors in methylcellulose containing stem cell factor (SCF), IL-3 and IL-6 for 6 weeks and subsequently in liquid medium containing SCF and IL-6 for another 6 to 8 weeks. Following sensitisation with human IgE, these cells released histamine dose-dependently upon activation by anti-IgE and calcium ionophores while compound 48/80 and substance P were relatively ineffective. When the effects of anti-asthmatic agents on anti-IgE-induced mediator release from these cells were compared, only the beta(2)-adrenoceptor agonists and phosphodiesterase inhibitors produced dose-dependent inhibition but not cromolyn or nedocromil. In total, mast cells cultured from human buffy coat progenitors shared similar functional properties of MC(T) subtype of mast cells found predominantly in human lung parenchyma and intestinal mucosa.

Functional characterization of human mast cells cultured from adult peripheral blood

Mast cells are important effector cells of allergy and techniques for culturing human mast cells have been developed in recent years. In the current investigation, we studied the phenotypic and functional characteristics of mast cells cultured from adult human peripheral blood mononuclear cells. Mature human mast cells were obtained by first culturing mononuclear cells in methylcellulose containing stem cell factor (SCF), IL-3 and IL-6 for six weeks and subsequently in liquid medium containing SCF and IL-6 for another six weeks. These cells expressed numerous basophilic cytoplasmic granules that were predominantly tryptase positive but chymase negative. Following sensitization with human IgE, these cells released histamine and synthesized prostaglandin D2 and cysteinyl-leukotrienes dose-dependently upon activation by anti-IgE and calcium ionophores. Compound 48/80 and substance P were ineffective. When the effects of anti-asthmatic agents on anti-IgE induced mediator release from these cells were compared, only the beta2-adrenoceptor agonists and phosphodiesterase inhibitors produced dose-dependent inhibition but not cromolyn. In total, mast cells cultured from human peripheral blood shared similar morphological, immunocytochemical and functional properties of enzymatically dispersed human lung mast cells. These cultured mast cells can be a convenient substitute for the in vitro studies of human lung mast cell reactions and may be useful for investigating the roles of mast cells in allergic diseases.

Tissue-specific renin-angiotensin system in pulmonary lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM), a multisystem disease found in middle-aged women, is characterized by cystic lung destruction and abdominal tumors (e.g., angiomyolipomas, lymphangioleimyomas), resulting from proliferation of abnormal-appearing, smooth muscle-like cells (LAM cells). The LAM cells, in combination with other cells, form nodular structures within the lung interstitium and in the walls of the cysts. LAM cells contain mutations in the tuberous sclerosis complex TSC1 and/or TSC2 genes, which lead to dysregulation of the mammalian target of rapamycin, affecting cell growth and proliferation. Proliferation and migration of vascular smooth muscle cells and production of angiogenic factors are regulated, in part, by angiotensin II. To determine whether a LAM-specific renin-angiotensin system might play a role in the pathogenesis of LAM, we investigated the expression of genes and gene products of this system in LAM nodules. mRNA for angiotensinogen was present in RNA isolated by laser-captured microdissection from LAM nodules. Angiotensin I-converting enzyme and chymase-producing mast cells were present within the LAM nodules. We detected renin in LAM cells, as determined by the presence of mRNA and immunohistochemistry. Angiotensin II type 1 and type II receptors were identified in LAM cells by immunohistochemistry and immunoblotting of microdissected LAM nodules. Angiotensin II is localized in cells containing alpha-smooth muscle actin (LAM cells). A LAM-specific renin-angiotensin system appears to function within the LAM nodule as an autocrine system that could promote LAM cell proliferation and migration, and could represent a pharmacologic target.

Mast cells in human bile duct obstruction

Surgical biopsy specimens obtained from 50 patients with secondary cholangitis caused by obstruction of the common bile duct were studied immunohistochemically. Data on the number and ultrastructural appearances of mast cells positive for tryptase, chymase, vasointestinal polypeptide (VIP), and substance P (SP) were obtained. The bile ducts from patients presenting combined chronic exacerbated cholangitis and chronic sclerotic cholangitis showed significantly higher numbers of mast cell types compared to the controls (P < 0.0001). Cases with sclerotic cholangitis alone had significantly lower number of cells than patients with chronic exacerbated cholangitis alone (P < or = 0.0001). Morphometric measurements of electron micrographs showed that mast cell granules containing VIP, SP and chymase were commensurable in size. Electron-lucent granules without reaction product (altered granules) and granules with focal distribution of the reaction product were observed in all types of mast cells. Furthermore, some nerve fibers positive for SP and VIP and serotonin-positive endocrine cells were observed in close proximity to the mast cells. In conclusion, the results of our study demonstrate the existence of different populations of mast cells, nerve structures and endocrine cells in the lower part of the human large bile duct, and suggest their participation in the development of pathological processes.

Relationship of Small Airway Chymase-Positive Mast Cells and Lung Function in Severe Asthma

Distal lung inflammation may be important in asthma pathophysiology. The goal of this study was to measure cellular inflammation in the large airway and four distal lung regions (small airway inner and outer wall, alveolar attachments, and peripheral alveolar tissue) and to correlate the specific inflammatory cells with several lung function parameters. Sections of concurrently obtained endobronchial and transbronchial/surgical biopsy tissue from 20 individuals with severe asthma were immunostained for T-lymphocyte, eosinophil, monocyte/macrophage, neutrophil, and two mast cell markers (tryptase and chymase). Specific cell distributions were determined and correlated with lung function measures. The number of inflammatory cells generally increased toward the periphery, but the percentage of T-lymphocytes, eosinophils, monocytes/macrophages, and neutrophils remained similar or decreased from large to small airways. In contrast, mast cell number, percentage, and the chymase-positive phenotype increased in small airway regions. After the analysis was adjusted for multiple comparisons, only chymase-positive mast cells significantly and positively correlated with lung function. Such a relationship was seen only in the small airway/alveolar attachments lung region (r(s) = 0.61-0.89; p </= 0.001 for all correlations). These data suggest that induction of chymase-positive mast cells, particularly in the small airway outer wall/alveolar attachments region, may be protective for lung function in severe asthma.

Selective alterations in mast cell subsets and eosinophil infiltration in two complementary types of intestinal inflammation: ascariasis and Crohn's disease

OBJECTIVE

Numbers of mast cells (MCs) of different subpopulations and the extent of eosinophil infiltration were compared in Crohn's disease and ascariasis. These two types of intestinal inflammation are complementary with regard to T cell response (TH1 versus TH2), prevalence and environmental factors.

METHODS

Histochemical, immunohistochemical and ultrastructural tools were applied to biopsies of morphologically uninvolved colon, ileum and duodenum from Crohn's and ascariasis patients, as well as resection margins and tissues from an experimental porcine ascariasis model. MC subsets were defined by their dye-binding properties, and their chymase content was analysed using biochemical tools.

RESULTS

The TH2 (IgE-mediated) response in ascariasis was characterised by a dramatic increase in mucosal- type MCs (MMCs) and eosinophils in both the mucosa and the deeper layers of the intestinal wall and a simultaneous decrease of connective tissue-type MCs (CTMCs). Uninvolved intestine of Crohn's patients showed moderate proliferation of CTMCs in the deeper layers of the intestinal wall, but a significant decrease of the MMCs, associated with moderate eosinophilia in all layers of the gut. Similar changes were present in the uninvolved duodenum of Crohn's patients. Comparable amounts of chymase could be extracted from mucosal and submucosal duodenum, with similar proportions of its two principal isoforms in each.

CONCLUSIONS

Our results indicate that T cell responses (TH1 or TH2) are associated with different MC subsets in intestinal inflammation. Changes remote from the focus of inflammation point to the systemic nature of the different MC responses.

Structural examination of tryptase- and chymase-positive mast cells in livers, containing metastases from gastrointestinal cancers

Human mast cells are categorized into mast cells positive only for tryptase (MC(T)) and mast cells positive for both tryptase and chymase (MC(TC)). The structural appearance of tryptase-, and chymase-positive mast cells in metastatic liver disease and the variations in MC(T) and MC(TC) numbers in accordance with the origin of the primary tumors have been described in the present study. Liver mast cells are analyzed immunocytochemically using tryptase and chymase and by quantitative morphometry in 30 patients with colorectal (n = 15), gastric (n = 8), and pancreatic (n = 7) cancers and in 5 control livers. The numbers of MC(T) and MC(TC) are increased in the extratumoral liver tissue (mainly portal tracts) as compared to controls. The numbers of MC(T) and MC(TC) in and around metastases with moderate or high grade of differentiation are statistically significantly higher, as compared to those with low grades of differentiation. The numbers of MC(TC) are greater than that of MC(T) in the extratumoral liver tissue and in metastases themselves. Ultrastructurally, mast cells immunostained with tryptase and chymase have three types of granules: electron dense granules with darkly precipitated reaction product, electron lucent granules without reaction product and electron lucent granules with sparse reaction product (altered granules). Both types of mast cells have small and large in size granules, resembling the MC(TC) phenotype described earlier. Tryptase-positive mast cells have granules with discrete scrolls and particulate and beaded pattern. Chymase-positive mast cells have granules with finely granular or particulate material. Substance P (SP)- and vasointestinal polypeptide (VIP)-positive mast cells are not observed in livers with metastases. The present study suggests that liver mast cells are mainly from the MC(TC) type, and are accumulated in peritumoral and metastatic areas. They may play a role in the formation of tumor stroma, or in tumor immunology in liver metastases from various primary gastrointestinal cancers.

Chymase-positive mast cells in small sized adenocarcinoma of the lung

Mast cells accumulate in angiogenesis-dependent situations of lung adenocarcinoma. Human mast cells are divided into two major subsets: MCT (mast cells with immunoreactivity for tryptase but not chymase) and MCTC (reactive for tryptase and chymase). Chymase is an important mediator of tissue remodeling, but research into chymase-containing mast cell subpopulations has been hampered by the lack of reagents suitable for use with formalin-fixed tissue. We stained chymase using CC1 antibody in 66 cases of small sized lung adenocarcinoma as well as CD34 and tryptase. There were significant positive correlations of microvessel counts with MCT-type and MCTC-type mast cell counts in lung adenocarcinomas. When analyzed according to Noguchi's classification, MCT-type and MCTC-type mast cells were significantly increased in Noguchi type-C tumors [localized bronchioloalveolar carcinoma (LBAC) with active fibroblastic proliferation] compared with in Noguchi type-A (LBAC) plus type-B tumors (LBAC with alveolar collapse). Members in the high-count group of MCTC-type but not MCT-type mast cells showed a significantly worse outcome than those in the low-count group in LBACs. Counting chymase-positive (MCTC-type) mast cells in tumor stroma may be a good prognosis predictor for LBACs, especially Noguchi type-C tumors.