Biomedical subjects

A Galvin

Publications and source records attributed to A Galvin.

6 recordsLinked to original sources

PubMed1999

Investigation of the expression of IL-1beta converting enzyme and apoptosis in normal and inflammatory bowel disease (IBD) mucosal macrophages.

Activated mucosal macrophages are derived from circulating monocytes and appear to play a major role in the pathogenesis of IBD. We have recently shown that IBD, but not normal, mucosal macrophages express the active form of IL-1beta converting enzyme (ICE) and are therefore capable of releasing mature IL-1beta. ICE expression by other mucosal cell types is unknown. Active ICE expression has also been implicated in apoptosis. The aim of this study was to investigate ICE expression (using an antibody that recognizes both active and precursor forms) in normal and IBD mucosa and to determine whether ICE-expressing macrophages are undergoing apoptosis. Normal and active IBD mucosal cells, in tissue sections and after isolation, were studied by immunohistochemistry and flow cytometry. In the mucosa, macrophages were the predominant ICE-expressing cell type. In contrast to normal, most IBD mucosal macrophages expressed ICE. Of IBD colonic macrophages 11.8 +/- 3.2%, and of normal colonic macrophages 6.6 +/- 0.6% expressed Apo2.7, a marker for apoptotic cells. Similar data were obtained when annexin V was used to identify cells undergoing apoptosis. DNA fluorescence flow cytometric analysis of normal and IBD lamina propria cells showed the presence of only small hypodiploid DNA peaks. We conclude that in the human intestinal mucosa, macrophages are the predominant ICE-expressing cell type. Expression of the active form of ICE and macrophage apoptosis are not interdependent. One mechanism of loss of resident macrophages from normal mucosa and of recruited macrophages from IBD mucosa is by apoptosis.

Apoptosis↗

PubMed1998

Differential lamina propria cell migration via basement membrane pores of inflammatory bowel disease mucosa.

BACKGROUND & AIMS: In active inflammatory bowel disease (IBD), the intestinal mucosa is infiltrated by polymorphonuclear cells (PMNs), lymphocytes, and monocytes from the systemic circulation. Using an ex vivo model, we have investigated luminally directed migration of cells out of the lamina propria. METHODS: Fresh untreated and deepithelialized mucosal samples were studied by electron microscopy. Cells migrating out of the lamina propria were investigated by immunohistochemistry and fluorescence-activated cell sorter analysis. RESULTS: In intact IBD mucosal samples, tunnels containing cells were prominent in the lamina propria matrix, and PMNs, but not other cell types, were prominent in the epithelium. In deepithelialized mucosal samples, the basement membrane was either destroyed or contained numerous large pores. During culture of deepithelialized mucosal samples, many cells (3.3 [+/-0.8] x 10(5) . g tissue-1 . h-1) migrated out of the lamina propria via basement membrane pores. PMNs and eosinophils were prominent during the first 3 hours of culture, but T cells predominated thereafter. Macrophages also migrated, but B cells were the minority population (<2%) at all times. CONCLUSIONS: In active IBD mucosa with an intact epithelium, luminally directed migration of lamina propria cells is restricted mainly to PMNs. After loss of the epithelium, other cell types also migrate into the lumen via numerous, large, basement membrane pores.

Basement Membrane↗

PubMed1998

Expression of alpha5 (CD49e) and alpha6 (CD49f) integrin subunits on T cells in the circulation and the lamina propria of normal and inflammatory bowel disease colonic mucosa.

Intestinal lamina propria T cells are believed to be derived, via the systemic circulation, from gut-associated lymphoid tissue. After migration into the lamina propria, T cells are capable of luminally directed migration following the loss of surface epithelial cells. For adhesion and migration within the extracellular matrix, T cells are likely to utilize the integrin family of adhesion molecules. The aim of this study was to quantitatively and qualitatively investigate the expression of alpha5 and alpha6 integrin subunits on the surface of human T cells that: (a) migrated out of the lamina propria, (b) remained resident within the matrix and (c) were present in the circulation. In both subpopulations of CD4 and CD8-positive T cells, from both normal and inflamed (inflammatory bowel disease) colonic mucosa, there were significantly fewer alpha5 and alpha6-positive cells than in the peripheral blood. In addition, there were significantly fewer alpha6 integrin molecules on the surface of CD4 and CD8-positive lamina propria T-cell subpopulations, compared with those in the circulation. Our studies suggest that, following migration into the lamina propria, there is down-regulation of alpha5 and alpha6 integrin-subunit expression on the surface of T cells. Molecules other than members of very late activation antigen-5 (VLA-5) (alpha5beta1) and VLA-6 (alpha6beta1) families of adhesion molecules are likely to be important in interactions with extracellular components in the lamina propria of normal and inflamed human colonic mucosa.

Antigens, CD↗

PubMed1998

Effect of Clostridium difficile toxin A on human colonic lamina propria cells: early loss of macrophages followed by T-cell apoptosis.

We have previously shown that Clostridium difficile toxin A induces detachment of human colonic epithelial cells from the basement membrane and subsequent cell death by apoptosis. Because these cells require adhesion-dependent signalling from the extracellular matrix for survival, their detachment from the basement membrane by other means also induces apoptosis. The role of toxin A in the induction of apoptosis therefore remains to be determined. In addition, sensitivities to C. difficile toxin A of lamina propria lymphocytes, macrophages, and eosinophils, which lie below the surface epithelium, are not known. In contrast to epithelial cells, these lamina propria cells do not require adhesion-dependent signalling from the extracellular matrix for survival, and this may allow the mechanisms of toxin A-induced cell death to be further investigated. The aim of this study was to investigate the effect of purified C. difficile toxin A on human colonic lamina propria T cells, macrophages, and eosinophils. We show that C. difficile toxin A induces loss of viability in isolated colonic lamina propria cell preparations containing the three different cell types in a dose- and time-dependent fashion. Exposure to high concentrations of the toxin led to loss of macrophages within 72 h. T-lymphocyte and eosinophil cell death was prominent at later time points and occurred by apoptosis. Exposure to toxin A also induced the production of tumor necrosis factor alpha by the isolated colonic lamina propria cells. However, the presence of neutralizing antibodies to this cytokine did not influence C. difficile toxin A-induced T-cell apoptosis. Moreover, purified T cells also underwent apoptosis following exposure to toxin A, implying that apoptosis occurred as a consequence of a direct interaction between T cells and the toxin. Our studies suggest that C. difficile toxin A is capable of suppressing human colonic mucosal immune responses by inducing early loss of macrophages followed by T-cell apoptosis.

Apoptosis↗

PubMed1995

Circulating human IgG autoanti-IgE antibodies in asthma patients block the binding of IgE to its high affinity receptor.

Aims-To investigate the ability of circulating human IgG autoanti-IgE antibodies from asthma patients to block the binding of IgE to the alpha chain of the high affinity receptor (FcepsilonRI).Methods-This involved the use of a well validated flow cytometric method to detect inhibition of FITC labelled IgE binding to a fibroblast cell line (CHK1E1) transfected with the alpha chain of FcepsilonRI.Results-IgG autoanti-IgE-containing sera blocked the binding of IgE-FITC to the CHK1E1 cells. No such inhibition was demonstrable with rheumatoid sera containing autoanti-IgG (that is, rheumatoid factor) but lacking autoanti-IgE. Percentage inhibition (up to 50%) of IgE binding to the CHK1E1 cells was directly related to the titre of IgG1, but not IgG4, autoanti-IgE in the sera tested (correlation coefficient 0.66, probability 0.003).Conclusions-The capacity of anti-IgE to block the binding of IgE to FcepsilonRI has important clinical implications, particularly in terms of downregulation of allergic reactions.

Journal Article↗

PubMed1993

Chemotherapy-induced differential changes in lymphocyte subsets and natural-killer-cell function in patients with advanced breast cancer.

To elaborate a rational approach to chemoimmunotherapy in humans, information is required as to how current cytotoxic chemotherapy regimens modulate patients' endogenous immune cells. We have studied a group of 16 advanced breast cancer patients who received cyclical cytotoxic chemotherapy (CMF-cyclophosphamide, methotrexate and 5-fluorouracil) and have documented the progressive differential effects of chemotherapy on endogenous immune cells as judged by changes in immunophenotype and absolute numbers of lymphocyte subsets, together with analysis of natural-killer-cell function. Cells with the immunophenotype of natural killer cells and lymphokine-activated killer cells (NK/LAK cells) were well retained, but their function was suboptimal. Additionally, CD8 T cells were well preserved, but the numbers of CD4 T cells decreased with succeeding cycles of chemotherapy; B-cell numbers decreased rapidly from the first cycle of chemotherapy. These cellular changes in humans indicate defined and precisely timed windows of opportunity for introducing in vivo, simple and direct immune stimulation of the cells modulated by chemotherapy, with the possibility of improving therapy and survival in this disease.

Antineoplastic Combined Chemotherapy Protocols↗