An improved procedure for the development of human mast cells from dispersed fetal liver cells in serum-free culture medium.

The in vitro development of human mast cells from fetal liver cells with recombinant human stem cell factor in serum-containing RPMI was compared to that in AIM-V media with and without serum. Compared to serum-containing media, AIM-V medium caused mast cells to develop earlier and in greater numbers. By 2 weeks, about 60% of cells in serum-free AIM-V medium were phenotypic mast cells, approximately 2 times the percentages in serum-containing media. By 6 weeks the percentages of mast cells were > or =80% under all conditions, but the number of mast cells was 3-4-fold greater in serum-free AIM-V medium than in serum-supplemented media. Mast cells obtained in serum-free AIM-V medium exhibited rounded nuclei, like tissue-derived mast cells; mast cells obtained in serum-supplemented media had segmented nuclei. By 10-12 weeks of culture about 40% of the AIM-V-derived cells showed strong chymase immunocytochemical staining, a pattern observed for only 14% of the cells in serum-containing media. AIM-V medium is a suitable medium for the development of human mast cells in vitro, and permits an earlier, more selective and greater expansion of mast cells than serum-containing media.

Dexamethasone inhibits the development of mast cells from dispersed human fetal liver cells cultured in the presence of recombinant human stem cell factor.

Human fetal liver cells cultured in the presence of recombinant human stem cell factor (rhuSCF) give rise to highly purified mast cell populations. This study examined the effect of steroid hormones on mast cell differentiation. Dispersed fetal liver cells cultured in the presence of rhuSCF at 50 ng/ml and in the presence or absence of various steroid hormones for 4 weeks, were analysed for the presence of mast cells by metachromatic staining with toluidine blue, by immunohistochemistry with a monoclonal antibody against tryptase, and by immunofluorescent flow cytometry with a monoclonal antibody against Kit. Dexamethasone added to the cultures at day 0 resulted in a dose-dependent inhibition of rhuSCF-induced mast cell differentiation with > 85% inhibition seen at a dose of 10(-6) M. A similar effect was seen with hydrocortisone, but not with oestradiol or progesterone. The addition of dexamethasone resulted in decreased DNA synthesis in 14-day-old cultured cells, as assessed by incorporation of bromodeoxyuridine. Addition of dexamethasone to 3-week-old SCF-dependent fetal liver mast cells had no significant effect on mast cell survival. Removal of dexamethasone after 3 weeks of culture with SCF did not result in mast cell development. Thus, dexamethasone inhibits SCF-induced development of mast cells from fetal liver cells, but shows no appreciable effect on developed mast cells.

Localization of rat tryptase to a subset of the connective tissue type of mast cell.

We examined the cellular distribution of rat tryptase in rat skin, lung, small intestine, and peritoneal lavage cells by immunohistochemical techniques. Tryptase purified to apparent homogeneity from rat skin was used to generate a goat polyclonal anti-rat tryptase antibody. Tryptase-containing cells were detected in lung, skin, and peritoneal lavage cells. Small intestine mucosa, on the other hand, showed few if any tryptase-positive cells. Sequential staining with Alcian blue and anti-tryptase antibody showed that tryptase is located only in mast cells. Sequential staining with safranin to identify the connective tissue type of mast cell and anti-tryptase antibody showed that tryptase resides only in this mast cell type. However, only a subpopulation of the safranin-stained mast cells contained tryptase. In lung, 53% of the mast cells stained with safranin; 94% contained tryptase. In skin, 80% stained with safranin; only 6% contained tryptase. In peritoneal cells, more than 95% of the mast cells were stained with safranin; 20% contained tryptase. In the bowel mucosa, where few cells are stained by safranin, no cells with tryptase were detected. The percentages of cells with chymase I that also contained tryptase were 80% and 84% for lung, 4% and 7% for skin, and 15% and 13% for peritoneal cells by respective simultaneous and sequential double labeling with anti-tryptase and anti-chymase I antibodies. This study suggests that the rat connective tissue type of mast cell is subdivided into two forms on the basis of the presence or absence of tryptase, whereas rat mucosal mast cells lack this enzyme. These results contrast with those in humans, in which tryptase is present in all mast cells, but are similar to mice, in which tryptase mRNA has been detected only in the connective tissue type.

Quantification of resident inflammatory cells in the human nasal mucosa.

BACKGROUND: To define the normal resident inflammatory cell population in the nasal mucosa, surgical specimens of human nasal turbinates were immunohistologically stained for various cell markers. METHODS: Freeze-dried paraffin-embedded sections were stained for lymphocyte cell-surface markers, and Carnoy's fixed sections were stained for mast cells and immunoglobulins. The numbers of stained cells were microscopically counted. RESULTS: T cells (CD3+ cells) were abundant in the lamina propria, and the number of CD4+ cells and CD8+ cells accounted for two thirds and one third of CD3+ cell number, respectively. Cells that stained for the alpha-chain of the interleukin-2 receptor (activated cells, CD25+) were limited and accounted for only 0.6% of CD3+ cell number. B cells (CD22+ cells) and monocytes and macrophages (CD14+ cells) were observed less frequently than T cells. Many immunoglobulin-producing cells were found in close proximity to the submucosal glands, and those cells were predominantly IgA+. Mast cells were widely distributed in the nasal mucosa, and about one third of these cells were stained for IgE molecules. Nonmast cells bearing IgE were rarely observed. CONCLUSION: Thus the dominant cell in the nasal mucosa is a CD3+, CD4+, CD25-lymphocyte.

Characterization of human mast cells developed in vitro from fetal liver cells cocultured with murine 3T3 fibroblasts.

Cocultures of dispersed human fetal liver cells with murine Swiss 3T3 fibroblasts resulted in the development of human mast cells after 1 to 4 weeks of culture. Mast cells were detected by immunohistochemistry using a murine monoclonal anti-tryptase antibody, before metachromasia appeared with toluidine blue. When subjected to double immunohistochemistry using murine monoclonal anti-chymase and anti-tryptase antibodies, 94% +/- 10% (SD) of the mast cells seen at day 30 of culture were of the MCT type. These results contrast with those obtained with human mast cells derived from cord blood mononuclear cells cocultured with murine 3T3 fibroblasts which are comprised of substantially greater numbers of MCTC cells, averaging 48% +/- 31% (SD) at day 30 of culture. Mast cells developed in vitro from fetal liver cells or cord blood mononuclear cells contained similar amounts (+/- SD) of histamine (0.9 +/- 0.5 pg/cell and 1.1 +/- 1 pg/cell, respectively) and tryptase (1.7 +/- 0.4 pg/cell and 1.9 +/- 1.2 pg/cell, respectively) on day 30 of culture. Fetal-liver-derived mast cells from a 30-day-old culture were identified by immunoelectron microscopy using gold-labelled antitryptase antibody. Typically, these mast cells appeared immature as they had large nuclear to cytoplasmic ratio and a small number of ill-formed cytoplasmic granules. For both fetal-liver- and cord-blood-derived mast cells, there was no evidence of conversion of the MCT type into the MCTC type provided by this study. These results suggest that commitment to develop as an MCT or MCTC type of mast cell may have occurred in mast cell precursors present in fetal liver and cord blood mononuclear cells, prior to granulation.

Histochemical and immunohistochemical characteristics of mast cells in nasal polyps.

In surgically excised nasal polyps, most epithelial mast cells were formalin sensitive, chloroacetate esterase (CAE) negative, and chymase negative. Thus, this represents a population of mast cells not identified by staining for CAE. On the other hand, most stromal mast cells were formalin resistant and CAE positive, and although there was some polyp-to-polyp variability in their content of neutral protease, most of these cells were positive for both tryptase and chymase. The percentage of metachromatic cells in the epithelium and the number of metachromatic cells per unit area of polyp tissue did not correlate with an index of allergy skin test reactivity or the serum IgE concentration. The percentage of mast cells surrounded by pericellular tryptase, suggesting activation/degranulation, was significantly higher in the stroma than in the epithelium. The findings demonstrate differences between the stroma and the epithelium in phenotype and state of activation of mast cells; these are postulated to be due to distinct microenvironmental factors that affect mast cells at these sites.

Mast cells in cutaneous mastocytosis: accumulation of the MCTC type.

Lesional (n = 15) and non-lesional (n = 10) skin of subjects with mastocytosis was analysed for the distribution and concentration of trypase positive, chymase negative mast cells (MCT) and tryptase positive, chymase positive mast cells (MCTC) cells and compared to normal skin (n = 23) and non-lesional skin of subjects with unexplained anaphylaxis or flushing episodes (n = 6). Skin biopsies were fixed in Carnoy's fluid and subjected to double immunohistochemical staining with biotinylated mouse monoclonal anti-chymase antibody followed by alkaline phosphatase-conjugated mouse monoclonal anti-tryptase antibody. MCTC cells were the only type of mast cells seen in all specimens analysed and in each case were more numerous in superficial compared to deep regions of dermis. The concentration (mean +/- s.d.) of mast cells in the superficial dermis of mastocytosis lesions (40 985 +/- 21 772 mast cells/mm3) was significantly increased over that in corresponding areas of non-lesional skin from subjects with mastocytosis (7178 +/- 3607 mast cells/mm3), skin from subjects with idiopathic anaphylaxis or flushing episodes (6974 +/- 3873 mast cells/mm3) and normal skin (7347 +/- 2973 mast cells/mm3). The exclusive presence of MCTC cells in skin lesions of mastocytosis which are characterized by non-malignant hyperplasia of mast cells suggests involvement of local tissue factors in mast cell recruitment and differentiation.

Two types of human mast cells that have distinct neutral protease compositions.

Two human mast cell types were identified by immunohistochemical techniques in skin, lung, and small intestine. One type contains the neutral proteases, tryptase and chymotryptic proteinase, and is termed the TC mast cell. The second type contains only tryptase and is termed the T mast cell. Both types are fixed better by Carnoy's fluid than by formalin. The percentage of mast cells accounted for by the T type was 12 in skin; 98 in mucosa and 13 in submucosa of small intestine; and 77 in bronchial/bronchiolar subepithelium, about 97 in bronchial/bronchiolar epithelium, and 93 in alveoli of lung. Dispersed lung cells contained 90% T mast cells. The mean area of TC mast cells (76 micron2) was slightly larger than that of T mast cells (66 micron2); however, there was such extensive overlap that individual mast cells belonging to different types could not be distinguished on the basis of size. The recognition of human mast cell types with distinct protease compositions suggests a higher level of complexity of human mast cell-mediated reactions than heretofore appreciated.