Biomedical subjects

S M Baddeley

Publications and source records attributed to S M Baddeley.

4 recordsLinked to original sources

PubMed1998

Human mast cells express stem cell factor.

Stem cell factor (SCF) is a major cytokine regulator of mast cell growth and function. The present study demonstrates that human mast cells are able to produce SCF. Constitutive synthesis of SCF mRNA was seen in the mast cells isolated from human lung and skin by RT-PCR. This was confirmed by in situ hybridization in conjunctival mast cells of both tryptase-only (MCT) and tryptase/chymase (MCTC) subsets. SCF protein product was found in conjunctival MCT and MCTC mast cells by immunohistochemistry. Soluble SCF protein was detected in the culture supernatant of isolated lung mast cells by ELISA, and cross-linkage of IgE receptor (Fc epsilon-RI) on the lung mast cells in culture did not alter SCF mRNA expression, or the secreted soluble SCF protein. This was consistent with the finding that levels of SCF mRNA expression in conjunctival mast cells were similar between normal subjects and patients with seasonal allergic conjunctivitis (SAC). This study shows that human mast cells themselves are a cellular source of SCF, as well as being target cells for this growth factor. SCF may regulate mast cell growth and function via both paracrine and autocrine mechanisms. The production of SCF by mast cells may be regulated via mechanisms other than IgE receptor-mediated pathways.

Cell Culture Techniques↗

PubMed1997

Seasonal allergic conjunctivitis is accompanied by increased mast cell numbers in the absence of leucocyte infiltration.

BACKGROUND: Seasonal allergic conjunctivitis (SAC) is the most common allergic disease to affect the eye, occurring alone or in association with allergic rhinitis. Infiltration with mast cells and eosinophils is characteristic of the chronic forms of allergic conjunctivitis such as vernal and atopic keratoconjunctivitis, and these cell types also contribute significantly to allergic inflammation in the skin. Indirect evidence for a similar pattern of cellular events in SAC comes from studies which demonstrate raised eosinophil and neutrophil numbers in conjunctival scrapings and elevated levels of mast cell tryptase in tears following allergen challenge. OBJECTIVE: To directly characterize the inflammatory cell infiltrate in SAC and to determine its clinical relevance. METHODS: We employed specific immunohistochemical staining to count mast cells, eosinophils and neutrophils in the conjunctival epithelium and lamina propria of eight atopic patients with SAC in, and 12 SAC patients out of the hay fever season. Sixteen patients with no history of ocular allergy were used as control subjects. RESULTS: Mast cells were absent from normal epithelium. During the pollen season median mast cell numbers in the lamina propria were found to be increased by 61% in patients with SAC compared with normals (P=0.012). Eosinophils were found in the lamina propria in less than half of the symptomatic patients with SAC and in only three patients were eosinophils present in the epithelium. The neutrophil numbers in the lamina propria of patients with SAC tended to be higher than normals but these changes did not reach statistical significance. CONCLUSION: These data based on the direct assessment of conjunctival tissue provide evidence that symptoms occur in SAC in the absence of detectable recruitment of eosinophils or neutrophils. This suggests that this disorder is related to mast cell-mediated changes.

Adult↗

PubMed1997

Immunolocalization of cytokines to mast cells in normal and allergic conjunctiva.

BACKGROUND: Recently, the potential role of mast cells in allergic reactions has been extended by the discovery that these cells synthesize, store and secrete multifunctional cytokines. Seasonal allergic conjunctivitis is characterized as an immediate hypersensitivity reaction, in which allergen binds to specific IgE on mast cells, leading to release of pre-formed and newly synthesized inflammatory mediators. OBJECTIVE: In this study we aimed to localize the cytokines IL-4, IL-5, IL-6, IL-8 and TNF alpha to conjunctival mast cells and to examine the relationship between mast cell-associated cytokines and allergic conjunctivitis. METHODS: Immunohistochemistry was performed on serial sections of conjunctival biopsies from patients with seasonal allergic conjunctivitis, in and out of the hay fever season, as well as from non-allergic volunteers. RESULTS: IL-4, IL-5, IL-6 and TNF alpha were localized to mast cells in normal and allergic conjunctiva. IL-8 was localized to mast cells in two patients with seasonal allergic conjunctivitis, one during and the other outside the pollen season. Using the monoclonal antibody 3H4, which identifies the secreted form of IL-4, biopsies from patients with active seasonal allergic conjunctivitis contained a significantly higher proportion of mast cells positive for IL-4, than those from out-of-season patients (P=<0.016). There was no difference between the two groups in the number of mast cells immunostained by the antibody 4D9 which identifies the stored form of IL-4. CONCLUSIONS: These results suggest that conjunctival mast cells can store a range of multifunctional cytokines and release IL-4 during active disease, which may give them an important role in upregulating allergic inflammation in the conjunctiva.

Adult↗

PubMed1995

Mast cell distribution and neutral protease expression in acute and chronic allergic conjunctivitis.

Allergic eye disease has a variety of clinical manifestations including seasonal atopic conjunctivitis (SAC), perennial atopic conjunctivitis (PAC), atopic keratoconjunctivitis (AKC), and atopic blepharoconjunctivitis (ABC). We have investigated the number, distribution and protease expression of mast cells in normal and diseased conjunctiva with the use of immunohistochemistry in water-miscible resin sections. The median mast cell densities in normal subjects were 17 mm-2 in the bulbar substantia propria and 9 mm-2 in tarsal substantia propria. Mast cells were absent from the normal conjunctival epithelium at both sites. Mast cell densities were increased in the bulbar substantia propria in SAC, AKC and ABC. Tarsal substantia propria showed a significant increase in mast cells in ABC and AKC disease states. Mast cells express a range of proteases which varies according to their anatomic site. Mast cells in connective tissue are described to contain tryptase, chymase, cathepsin-G and carboxypeptidase-A, whereas mucosal mast cells contain only tryptase. In the diseased conjunctiva there was a marked reduction in proteases other than tryptase in the intraepithelial mast cells. There were also significant reductions in protease expression other than tryptase in the bulbar substantia propria in AKC and ABC. There appear to be specific alterations in the distribution of mast cells in the sub-categories of allergic eye disease. The distinction between mucosal and connective tissue mast cell phenotypes is not clear-cut and may depend on the functional state of the mast cells in relation to the microenvironment.

Acute Disease↗