Search results for "superantigen"
showing 10 items of 27 documents
Distribution and kinetics of superantigen-induced cytokine gene expression in mouse spleen.
1993
The polyclonal stimulation of T cells by bacterial superantigens is involved in the pathogenesis of the toxic shock syndrome in certain staphylococcal and streptococcal infections. Here we describe the onset and kinetics of superantigen-induced cytokine production in situ in spleens of normal BALB/c mice monitored at the level of cytokine mRNA expression by in situ hybridization. Messenger RNAs for interleukin 2 (IL-2), interferon gamma, and tumor necrosis factors (TNF) alpha and beta were not expressed at detectable levels in spleens of unstimulated animals but became visible already 30 min after intraperitoneal application of 50 micrograms staphylococcal enterotoxin B. All mRNA levels sho…
Modulation of Contact Sensitivity Responses by Bacterial Superantigen
1995
Superantigens are potent modulators of the immune system, especially T cells. Therefore, we determined the influence of superantigens on the T-cell-mediated immune response, contact sensitivity. We chose the combination of staphylococcal enterotoxin B (SEB) as superantigen and 2,4-dinitrofluorbenzene (DNFB) as the contact sensitizer, because in BALB/c mice SEB reacts almost exclusively with V beta 8+ T cells, and these cells are capable of transferring contact sensitivity to DNFB from sensitized donors to naive syngeneic recipients. Pretreatment with a single intradermal injection of 50 ng SEB 24 h before DNFB exposure at the same site on the lower abdomen enhanced the induction of contact …
Distribution of emm types among group A streptococcal isolates from Serbia.
2010
AbstractThis is the first study concerning the molecular epidemiology of group A streptococcus in Serbia and includes 145 isolates from patients with various infections during the period 2001–2007. The emm types, superantigen profile and susceptibility pattern were determined. Among 31 emm types identified, the most prevalent were emm6, emm12, emm1, and emm58. All isolates showed uniform antimicrobial susceptibility to all tested antibiotics, with the exception of tetracycline and erythromycin (41% and 0.7% resistant strains, respectively). Significant heterogeneity of emm types was found, with a high frequency of emm6 and emm58, as well as a considerable prevalence of tetracycline resistan…
T lymphocyte-stimulating microbial toxins as ?superantigens?
1991
Infectious pathogens generally have to cope with the host's adaptive immune system, i.e., T and B lymphocytes. Common evasion mechanisms in this complex interaction are antigenic variations, the escape to immunologically priviledged sites or the use of immunosuppressive mechanisms. Many bacteria and other microorganisms eleborate soluble factors or toxins that act suppressively on cells of the immune system, such as pore-forming molecules or proteins that interfere with the function of G proteins. Gram-positive cocci and a mycoplasma have developed an extremely potent mechanism of T cell stimulation by closely mimicking recognition of specific antigen. From the functional similarity to anti…
Major histocompatibility complex class II binding site for streptococcal pyrogenic (erythrogenic) toxin A.
1994
Streptococcal pyrogenic exotoxin A (SPEA) is an important pathogenicity factor of group A streptococci. It is a member of the family of „superantigens” produced by Staphylococcus aureus and Streptococcus pyogenes and its T lymphocyte stimulating activity is involved into the pathogenesis of certain diseases caused by pyogenic streptococci. In this study we have produced and characterized recombinant SPEA molecules in Escherichia coli. These molecules are indistinguishable from natural SPEA in both T cell stimulatory and HLA class II binding activities. Human class II molecules are more efficient than mouse class II molecules in presenting SPEA to T cells. In binding tests to major histocomp…
Recombinant epidermolytic (exfoliative) toxin A of Staphylococcus aureus is not a superantigen
1992
The epidermolytic (exfoliative) toxins produced by Staphylococcus aureus cause epidermolysis and skin blistering. In addition, they have been implicated to belong to the group of T lymphocyte stimulating molecules known as "superantigens". Here we show that recombinant epidermolytic toxin A produced in S. aureus is not mitogenic for human and murine T lymphocytes. We discuss the possibility that minute contaminations of highly mitogenic exoproteins may cause the mitogenicity in several proteins that are reported to be superantigens.
Natural and induced apoptosis during lymphocyte development in the axolotl
1999
Lymphocytes apoptosis was characterized in a urodele amphibian, the axolotl, by morphology using electron microscopy and by flow cytometry after propidium iodide staining, as well as by biochemical criteria with the detection of DNA ladders after glucocorticoid treatment. The morphological and biochemical features observed in treated axolotls are in accordance with the criteria of apoptosis found in different models of mammalian lymphocyte programmed cell death. The onset of natural apoptosis was then detected by DNA fragmentation in thymus and in spleen during lymphocyte development and ontogenesis. A typical DNA ladder characteristic of apoptosis is detectable in the thymus as early as 5 …
Report of toxic shock syndrome toxin 1 (TSST-1) from Staphylococcus aureus isolated in food handlers and surfaces from foodservice establishments.
2012
A set of 53 Staphylococcus aureus isolates collected from food handlers and foodservice establishments in Spain was analyzed for toxic shock syndrome toxin (TSST-1) production. S. aureus strains were isolated from 908 samples collected from different surfaces such as dish towels, workers’ hands, cutting boards, stainless steel tables and slicers, but they were not detected neither in clean plates nor in kitchen knives. Only one food worker hand has been reported to be contaminated by TSST-1 in a restaurant. Despite this, proper hygiene practices should be respected for the surfaces of contact with food, as well as for the hands of the manipulators This is the first article, in Spain, that r…
Cutaneous Exposure to the Superantigen Staphylococcal Enterotoxin B Elicits a T-Cell-Dependent Inflammatory Response
1996
We analyzed the impact of superantigens secreted by skin-colonizing Staphylococci on the skin and the associated lymphoid tissue following epicutaneous application and intracutaneous injection of small amounts of staphylococcal enterotoxin B (SEB). A single intracutaneous injection of 50 ng of SEB elicited a strong inflammatory response in the skin of BALB/c mice. Three to 6 h later, we observed langerhans cell activation, mast cell degranulation, vasodilation, upregulation of ICAM-1, and induction of VCAM-1 on dermal blood vessels, with vascular adhesion of granulocytes. by 12 to 24 h, cell infiltration of the dermis increased, reaching the epidermis. Among the infiltrating leukocytes, a s…
An MHC class II-expressing T cell clone presenting conventional antigen lacks the ability to present bacterial superantigen.
1995
We have analyzed the response of rat T cells to myelin basic protein (MBP) and the bacterial superantigen, staphylococcal enterotoxin E (SEE). Rat T cells reactive with MBP can respond to SEE presented by spleen cells but not to SEE presented by LOA, a rat T cell clone that expresses both I-A and I-E MHC class II molecules, even though LOA is much more efficient than splenic APC in the presentation of MBP. The inability of LOA to present superantigen is not due to a structural difference in MHC II molecules between LOA and the splenic APC or to differential expression of major accessory/adhesion molecules, including CD2, CD5, CD4 and CD44, on LOA. The non-responsiveness of SEE/LOA-induced T…