| 1. |
- Elgbratt, Kristina, 1969-, et al.
(författare)
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A quantitative study of the mechanisms behind thymic atrophy in G alpha i2-deficient mice during colitis development
- 2012
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Ingår i: PLOS ONE. - San Francisco, USA : Public Library of Science. - 1932-6203. ; 7:5
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Tidskriftsartikel (refereegranskat)abstract
- Mice deficient for the G protein subunit G alpha i2 spontaneously develop colitis, a chronic inflammatory disease associated with dysregulated T cell responses. We and others have previously demonstrated a thymic involution in these mice and an aberrant thymocyte dynamics. The G alpha i2(-/-) mice have a dramatically reduced fraction of double positive thymocytes and an increased fraction of single positive (SP) thymocytes. In this study, we quantify a number of critical parameters in order to narrow down the underlying mechanisms that cause the dynamical changes of the thymocyte development in the G alpha i2(-/-) mice. Our data suggest that the increased fraction of SP thymocytes results only from a decreased number of DP thymocytes, since the number of SP thymocytes in the Gai2(-/-) mice is comparable to the control littermates. By measuring the frequency of T cell receptor excision circles (TRECs) in the thymocytes, we demonstrate that the number of cell divisions the G alpha i2(-/-) SP thymocytes undergo is comparable to SP thymocytes from control littermates. In addition, our data show that the mature SP CD4(+) and CD8(+) thymocytes divide to the same extent before they egress from the thymus. By estimating the number of peripheral TREC+ T lymphocytes and their death rate, we could calculate the daily egression of thymocytes. G alpha i2(-/-) mice with no/mild and moderate colitis were found to have a slower export rate in comparison to the control littermates. The quantitative measurements in this study suggest a number of dynamical changes in the thymocyte development during the progression of colitis.
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| 2. |
- Elgbratt, Kristina, 1969, et al.
(författare)
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Aberrant T-cell ontogeny and defective thymocyte and colonic T-cell chemotactic migration in colitis-prone Galphai2-deficient mice
- 2007
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Ingår i: Immunology. - : Wiley. - 0019-2805 .- 1365-2567. ; 122:2, s. 199-209
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Tidskriftsartikel (refereegranskat)abstract
- Galphai2-deficient mice, which spontaneously develop colitis, have previously been reported to have an increased frequency of mature, single positive thymocytes compared to wild-type mice. In this study we further characterized the intrathymic changes in these mice before and during overt colitis. Even before the onset of colitis, Galphai2(-/-) thymi weighed less and contained fewer thymocytes, and this was exacerbated with colitis development. Whereas precolitic Galphai2(-/-) mice had unchanged thymocyte density compared to Galphai2(+/-) mice of the same age, this was significantly decreased in mice with colitis. Thymic atrophy in Galphai2(-/-) mice involved mainly the cortex. Using a five-stage phenotypic characterization of thymocyte maturation based on expression of CD4, CD8, TCRalphabeta, CD69 and CD62L, we found that both precolitic and colitic Galphai2(-/-) mice had significantly increased frequencies of mature single-positive CD4(+) and CD8(+) medullary thymocytes, and significantly reduced frequencies and total numbers of immature CD4(+) CD8(+) double-positive thymocytes compared to Galphai2(+/-) mice. Furthermore, cortical and transitional precolitic Galphai2(-/-) thymocytes showed significantly reduced chemotactic migration towards CXCL12, and a trend towards reduced migration to CCL25, compared to wild-type thymocytes, a feature even more pronounced in colitic mice. This impaired chemotactic migration of Galphai2(-/-) thymocytes could not be reversed by increased chemokine concentrations. Galphai2(-/-) thymocytes also showed reduced expression of the CCL25 receptor CCR9, but not CXCR4, the receptor, for CXCL12. Finally, wild-type colonic lamina propria lymphocytes migrated in response to CXCL12, but not CCL25 and, as with thymocytes, the chemokine responsiveness was significantly reduced in Galphai2(-/-) mucosal lymphocytes.
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| 3. |
- Elgbratt, Kristina, 1969
(författare)
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Characteristics and Consequences of Thymic Involution in Inflammatory Bowel Disease. Experimental studies in G?i2-deficient and DSS-induced Colitis as well as in IBD patients
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Characteristics and Consequences of Thymic Involution in Inflammatory Bowel Disease. Experimental studies in G?i2-deficient and DSS-induced Colitis as well as in IBD patients Kristina Elgbratt Department of Microbiology and Immunology, Institute of Biomedicine, The Sahlgrenska Academy, G?teborg University, G?teborg Sweden Inflammatory Bowel Disease (IBD) is a chronic relapsing inflammatory disorder of the gastrointestinal tract, comprising ulcerative colitis and Crohn?s disease. Alterations in T cell subsets, an important cell type in cell-mediated immune responses in the adaptive immune system, are certainly an element contributing to disease development. The relationship between disease and T-cell maturation in the thymus is, however, poorly understood. The present study investigates intrathymic changes as well as the consequence of thymic involution by analysis of recent thymic emigrants in peripheral blood and lymphoid tissue in two different mouse models for colitis; G?i2-deficient mice and mice with DSS-induced colitis, as well as in IBD patients. Before the onset and during colitis, G?i2-/- mice demonstrate thymic involution, whereas in DSS-induced colitis the thymic atrophy is transient, being evident during the acute phase of colitis but reversed during the chronic phase. The frequency of medullary mature thymocytes was increased in both models, but the intrathymic changes were mainly seen in the cortex and involved reduced both frequencies and absolute numbers of cortical thymocyte subsets as well as impaired chemotactic responses towards the chemokines CXCL12 and CCL25. The impaired migration was not limited to the thymus as reduced responsiveness to CXCL12 was seen also in colonic lymphocytes from G?i2-/- mice. In mice with DSS-induced colitis, an increased frequency of the most immature subpopulation of double negative (DN) thymocytes and a proportional decrease in the most mature DN thymocytes correlated with the severity of colitis. These results strongly indicate that an aberrant T cell ontogeny is associated with development of colitis. It is unknown whether thymic atrophy is evident also in IBD patients. Due to the unavailability of human thymus tissue from IBD patients for such studies, one aspect of thymus function was evaluated by analysis of the levels of T cell receptor excision circles (TRECs), a marker for recent thymic emigrants (RTEs), in T lymphocytes from peripheral blood and the intestinal mucosa,. This analysis revealed reduced levels of RTEs in peripheral blood from IBD patients, irrespective of the expression of the mucosal homing receptor integrin ?4?7. In strong contrast to peripheral blood, an increased level of TRECs was found in the intestinal musosa, indicative of an instant recruitment of recent thymic emigrants into the intestine. These results were seen in both UC and CD -patients but were more pronounced in UC patients, and could not be explained by enhanced extrathymic T cell maturation within the mucosa. Preliminary data also indicate that the TRECs levels in the mucosa are not influenced by the activity of the disease. A similar analysis of TRECs levels was performed in colitic G?i2-/- mice but decreased levels were found both in peripheral blood and intestinal mucosa. However, a massive proliferation of memory/effector T cells, especially in the mucosa, disguised the true level of recent thymic emigrants in this compartment. Thus, chronic intestinal inflammation in IBD is clearly associated with changes in T cell ontogeny and thymic output. It is likely that this influences the peripheral T cell population and further studies would reveal whether this leads to lower ability for T cell mediated immunoregulation and/or the presence of autoreactive T cell clones. Key words: Inflammatory bowel disease, G?i2-/- mice, dextran sodium sulfate, thymocytes, T cell receptor excision circles (TRECs), recent thymic emigrants. ISBN 978-91-628-7302-8, G?teborg 2007
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| 4. |
- Fredin, Maria Fritsch, 1970, et al.
(författare)
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Dextran sulfate sodium-induced colitis generates a transient thymic involution--impact on thymocyte subsets.
- 2007
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Ingår i: Scandinavian journal of immunology. - : Wiley. - 0300-9475 .- 1365-3083. ; 65:5, s. 421-9
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Tidskriftsartikel (refereegranskat)abstract
- One of the most widely used animal models for inflammatory bowel disease (IBD) is the dextran sulfate sodium (DSS)-induced colitis. We have previously reported that 5 days administration of DSS in C57Bl/6J mice induces a colonic inflammation that progresses into chronicity after DSS removal, whereas in BALB/cJ mice the inflammation resolves within 4 weeks post-DSS. Here we show that both thymic size and thymocyte numbers dramatically decreased in the acute phase of inflammation in C57Bl/6 mice, 7 days after DSS withdrawal. Mature, CD4(+) and CD8(+) single positive (SP) CD69(lo) CD62L(hi) thymocytes were enriched in these mice, accompanied by a major decrease in the number of immature double positive (DP) thymocytes. However, the different maturation stages within the DP thymocyte subset were unchanged between healthy and inflamed C57Bl/6J mice. Interestingly, as the inflammation progressed into the chronic phase, the thymus recovered and 2 weeks after the acute inflammatory phase all the thymic parameters investigated in this study were restored to normal. In contrast, BALB/cJ mice only develop mild thymic alterations. Nevertheless, we found that within the double negative (DN) thymocytes an increased frequency and also total numbers of CD44(+) CD25(-) (DN1) cells correlated with the severity of colitis, and that the frequency of CD44(-) CD25(-) (DN4) thymocytes decreased proportionally in the acute phase in BALB/cJ mice. Our observations suggest that the thymic effects are intimately connected to the intestinal inflammatory response in colitis regardless of the inflammatory stimuli.
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| 5. |
- Hansson, Malin, 1967, et al.
(författare)
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Dendritic cells express CCR7 and migrate in response to CCL19 (MIP-3beta) after exposure to Helicobacter pylori
- 2006
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Ingår i: Microbes Infect. - : Elsevier BV. - 1286-4579. ; 8:3, s. 841-50
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Forskningsöversikt (refereegranskat)abstract
- Helicobacter pylori infection induces chronic inflammation in the gastric mucosa with a marked increase in the number of lymphoid follicles consisting of infiltrating B and T cells, neutrophils, dendritic cells (DC) and macrophages. It has been suggested that an accumulation of mature DC in the tissue, resulting from a failure of DC to migrate to lymph nodes, may contribute to this chronic inflammation. Migration of DC to lymph nodes is regulated by chemokine receptor CCR7, expressed on mature DC, and the CCR7 ligands CCL19 and CCL21. In this study we analysed the maturation, in vitro migration and cytokine production of human DC after stimulation with live H. pylori. For comparison, DC responses to non-pathogenic Escherichia coli bacteria were also evaluated. Stimulation with H. pylori induced maturation of DC, i.e. up-regulation of the chemokine receptors CCR7 and CXCR4 and the maturation markers HLA-DR, CD80 and CD86. The H. pylori-stimulated DC also induced CD4(+) T-cell proliferation. DC stimulated with H. pylori secreted significantly more interleukin (IL)-12 compared to DC stimulated with E. coli, while E. coli-stimulated DC secreted more IL-10. Despite low surface expression of CCR7 protein following stimulation with H. pylori compared to E. coli, the DC migrated equally well towards CCL19 after stimulation with both bacteria. Thus, we could not detect any failure in the migration of H. pylori stimulated DC in vitro that may contribute to chronic gastritis in vivo, and our results suggest that H. pylori induces maturation and migration of DC to lymph nodes where they promote T cell responses.
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| 6. |
- Kumawat, Ashok Kumar, et al.
(författare)
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Microscopic colitis patients have increased frequencies of Ki67+proliferating and CD45RO+ active/memory CD8+ and CD4+8+ mucosal T cells
- 2013
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Ingår i: Journal of Crohn's & Colitis. - Oxford, United Kingdom : Oxford University Press. - 1873-9946 .- 1876-4479. ; 7:9, s. 694-705
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Tidskriftsartikel (refereegranskat)abstract
- Background: Collagenous colitis (CC) and lymphocytic colitis (LC) are chronic inflammatory bowel disorders of unknown etiology. This study investigated phenotypic characteristics of the mucosal lymphocytes in CC and LC.Methods: Lamina propria and intraepithelial lymphocytes (LPLs, IELs) isolated from mucosal biopsies from CC (n = 7), LC (n = 6), as well as LC or CC patients in histopathological remission, (LC-HR) (n = 6) and CC-HR (n = 4) and non-inflamed controls (n = 10) were phenotypically characterized by four-color flow cytometry.Results: The proportions of CD8+ IELs were increased in CC and LC (p < 0.01) compared to controls. Increased proportions of CD45RO+CD8+ IELs and LPLs were observed in LC and even more in CC patients (p < 0.01). Both CC (p < 0.05) and LC patients had elevated proportions of CD4+8+ IELs and LPLs compared to controls. The proportions of CD45RO+ cells were increased in CD4+8+ IELs and LPLs (p < 0.05) in CC and LC patients compared to controls. Both CC (p < 0.05) and LC patients had higher proportions of Ki67+CD8+ IELs and LPLs compared to controls.In contrast, decreased proportions of CD4+ LPLs were observed in CC and LC as well as CD4+ IELs in LC compared to controls. Increased proportions of Ki67+CD4+ IELs and LPLs (p < 0.05) were observed in CC and LC patients. CC-HR but not LC-HR patients demonstrated normalized proportions of both IELs and LPLs compared to CC and LC patients respectively.Conclusion: LC and CC patients have differences in mucosal lymphocyte subsets, with increased proportions of Ki67+ and CD45RO+ CD8+ and CD4+8+ mucosal T cells.
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| 7. |
- Kumawat, Ashok Kumar, 1982-, et al.
(författare)
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Reduced T cell receptor excision circle levels in the colonic mucosa of microscopic colitis patients indicate local proliferation rather than homing of peripheral lymphocytes to the inflamed mucosa
- 2013
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Ingår i: BioMed Research International. - New York, USA : Hindawi Publishing Corporation. - 2314-6133 .- 2314-6141.
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Tidskriftsartikel (refereegranskat)abstract
- Dysregulated T cell responses in the intestine may lead to chronic bowel inflammation such as collagenous colitis (CC) and lymphocytic colitis (LC), together known as microscopic colitis (MC). Having demonstrated increased local T cell responses in the intestinal mucosa of MC patients, we investigated the recent thymic emigrants by measuring T cell receptor excision circle (TREC) levels in the colonic biopsies from CC (n = 8), LC (n = 5), and CC or LC patients in histopathological remission (CC-HR, n = 3) (LC-HR, n = 6), non-inflamed diarrhoea patients (n = 17), and controls (n = 10) by real-time PCR. We observed lower median TREC levels in both CC and LC patients as well as in LC-HR patients compared to controls. In contrast to MC patients, non-inflamed diarrhoea patients presented with enhanced TREC levels compared to controls. None of the recorded differences did, however, reach statistical significance. A trend towards increased relative expression of CD3 was noted in all MC subgroups examined and reached statistical significance in LC patients compared to controls. In conclusion, reduced TRECs level in the colonic mucosa, together with our previously demonstrated enhanced expression of Ki67(+) T cells, suggests local expansion of resident T lymphocytes in the inflamed mucosa of MC patients.
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| 8. |
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