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C Löfman

Publications and source records attributed to C Löfman.

6 recordsLinked to original sources
PubMed2001

The allergenic yeast Malassezia furfur induces maturation of human dendritic cells.

BACKGROUND: The yeast Malassezia furfur (M. furfur), present in the normal microflora of human skin, can act as an allergen that incites specific IgE reactivity and T cell proliferation in atopic dermatitis (AD) patients. The role of antigen presenting dendritic cells (DCs) in the onset and maintenance of AD is not well established. OBJECTIVE: The objective of the present study was to assess whether the interaction of M. furfur with human DCs will result in DC maturation, cytokine production and lymphocyte proliferation. METHODS: Monocyte-derived dendritic cells (MDDCs) were generated from human peripheral blood. Immature MDDCs were cultured with or without M. furfur or plastic beads, and with or without CD40L stimulation. Interaction of yeast cells by MDDCs was studied by time-lapse photography and cytokines were detected in culture supernatants with ELISA. The ability of MDDCs pre-incubated with M. furfur to induce proliferation in autologous lymphocytes was measured by [(3)H]-thymidine incorporation. RESULTS: Time-lapse photography showed that the majority of immature MDDCs internalized whole M. furfur yeast cells within 1 h. The presence of M. furfur induced maturation (CD83 expression) of MDDCs, and up-regulation of the costimulatory molecules CD80 and CD86. Production of TNF-alpha, IL-1 beta and IL-18 by MDDCs increased significantly (P < 0.05 for TNF-alpha and IL-1 beta, and P < 0.01 for IL-18) after the addition of M. furfur, while IL-10 and IL-12p70 levels remained unaltered. The CD40L-stimulated IL12p70 production by MDDCs was decreased in the presence of M. furfur (P < 0.05). Finally, immature MDDCs pre-incubated with M. furfur induced a proliferative response in autologous CD14-depleted peripheral blood mononuclear cells, in a dose-dependent manner. CONCLUSION: The data indicate that immature MDDCs can internalize the opportunistic yeast M. furfur. This process was associated with MDDC maturation, production of pro-inflammatory and immunoregulatory cytokines, which might favour induction of a Th2-type immune response, and a capacity to stimulate lymphocyte proliferation. This chain of events most likely contributes to the inflammatory reaction in AD.

Allergens↗
PubMed2001

IgE-mediated mast cell degranulation and recovery monitored by time-lapse photography.

BACKGROUND: Mast cells are long-lived resident cells that are of great importance in an allergic reaction. It has previously been suggested that after IgE-mediated degranulation mast cells can undergo regranulation. Such a process is probably of great importance with respect to the severity and perpetuation of the allergic response. OBJECTIVE: Our purpose was to investigate whether mast cells recover from degranulation and whether they still have the potential to release a granule-associated mediator and upregulate certain cytokine genes. METHODS: Mouse mast cells were repeatedly activated by IgE and specific antigen with a 24-hour or 48-hour interval. During each of the 2 activation stages, release of beta-hexosaminidase was measured by means of enzymatic colorimetric analysis, and IL-13 and IL-6 mRNA was detected by ribonuclease protection assay. Both scanning electron microscopy and time-lapse photography were used to reveal the process of mast cell recovery. RESULTS: We found that re-activation of degranulated mast cells in response to high-affinity IgE-receptor cross-linkage triggers beta-hexosaminidase release and upregulation of IL-13 and IL-6 gene expression levels similar to what is seen in the initial activation. Scanning electron microscopy documented cells at various stages during the recovery process 30 minutes after the activation. With time-lapse photography, a single cell that had undergone degranulation could be visualized consecutively during its recovery process. CONCLUSION: Mast cells can recover after an IgE-mediated activation and can repeatedly release beta-hexosaminidase and express IL-6 and IL-13 mRNA after re-activation.

Animals↗
PubMed2000

Helicobacter pylori entry into human gastric epithelial cells: A potential determinant of virulence, persistence, and treatment failures.

BACKGROUND AND OBJECTIVES: Intracellular location of Helicobacter pylori in human gastric epithelial cells has been observed in biopsies. Whether this reflects an ability to invade host cells and establish an intracellular niche remains to be determined. METHODS: The interactions between a clinical isolate of H. pylori and primary cell cultures from human gastric epithelium or the human epithelial cell line HEp-2 were monitored using time-lapse photography. This technique allows studies of the dynamics of host-microbial interactions. RESULTS: H. pylori cells readily approached and established close contacts with epithelial cells followed by uptake of the bacteria into the cellular cytoplasm. Entry into epithelial cells was achieved through an active process of bacterial motility and penetration of the cell membranes. In conventional invasion assays using HEp-2 cells, an increased internalization in a strain producing the vacuolating cytotoxin was observed, compared to the isogenic VacA knockout mutant. CONCLUSION: Invasion of gastric epithelium represents a hitherto unappreciated trait of H. pylori that could contribute to the bacterium's ability to establish persistent infection that evades the mucosal immune defense and sometimes also antimicrobial therapy. A small number of bacterial cells with a transient intracellular habitat could serve as a seeder population, providing a backup for a constantly challenged and fluctuating luminal population.

Antigens, Bacterial↗
PubMedDate not supplied

Internalization of cellular fragments in a human embryo: time-lapse recordings.

An observation is reported of internalization of a cellular fragment into a blastomere from a human embryo, as documented by time-lapse photography. The fragment, created during the first mitotic cleavage was reabsorbed into one of the mother blastomeres in less than 5 min. The time-lapse sequence, shown here as a series of still photographs, provides the first direct evidence that cellular fragments in human embryos can 'disappear' during the culture period, a phenomenon that is common in human IVF. The time-lapse sequence itself may be viewed on the internet at www.rbmonline.com/Article/633.

Blastomeres↗
PubMedDate not supplied

A method for longitudinal microscopic in vivo examinations of morphology, vascularity, and motility in the ovary and the oviduct of the rat.

OBJECTIVE: We developed an in vivo model to enable observation of dynamic changes in morphology, vascularity, and motility of the rat adnexa. METHODS: Immature Sprague-Dawley rats (n = 16) were primed with equine chorionic gonadotrophin (eCG;15 IU) followed by human chorionic gonadotrophin (hCG; 15 IU) 48 hours later to induce ovulation. The experiments were performed during prolonged (up to 12 hours) thiobarbiturate anesthesia. During laparotomy the periovarian bursa was retracted, whereafter the oviductal-ovarian complex was submerged into an organ chamber. Water immersion lenses (4x-40x; final magnification up to 810x) enabled detailed observations that were recorded on Beta-SP videotape. RESULTS: Capillary flow was monitored easily. At the level of the follicle, top blood flow velocity variations (8-10 per minute) were observed in the microvasculature. Ovulations were followed in detail, and oocyte-cumulus complexes were seen later in the oviductal ampulla. Regular contractions in the oviduct were synchronous with the oocyte-cumulus complexes moving back and forth in the oviductal lumen over a distance of about 900 microm. These contractions were more frequent (13-16 per minute) in the postovulatory phase compared with the time before ovulation (9-10 per minute). The oviductal contractions were initiated alternately from either end of the ampulla and were accompanied by a denudation of the oocytes, with a stream of cumulus cells seen moving in an abovarian direction in between contractions. CONCLUSION: High-magnification video recording in vivo was useful for capturing microcirculatory events as well as structural and functional changes of the ovary and the oviduct.

Anesthesia↗