PubMed Health⌕ Search

Biomedical subjects

A Tärnvik

Publications and source records attributed to A Tärnvik.

At least 73 records · Page 4Linked to original sources
PubMed1989

Molecular cloning and expression of a T-cell stimulating membrane protein of Francisella tularensis.

The isolation and expression in Escherichia coli of a gene encoding a T-cell stimulating 17 kiloDalton (kDa) membrane protein of Francisella tularensis is described. A genomic library of DNA from the live vaccine strain LVS of F. tularensis was constructed in the E. coli expression vector phage lambda gt11. The library was probed with antibodies directed against the 17 kDa protein. One recombinant phage was isolated, containing a 2.8 kilobase (kb) DNA insert. The insert was cleaved and a resulting 1.2 kb fragment was found to express the 17 kDa protein. The 1.2 kb fragment was inserted in the high copy number plasmid pUC18 and expressed in E. coli. Membrane preparations of these bacteria induced a response in T cells from F. tularensis-primed individuals but not in T cells from non-primed individuals. The cloned gene may become useful in studies on host interaction with F. tularensis and enable a precise identification of bacterial structures involved in the T-cell response.

Adult↗
PubMed1989

Complement activation in plasma exchange by single filtration and centrifugation and in cascade filtration.

C3d was assayed in samples of blood plasma obtained before and after centrifugation, single filtration or cascade filtration, and also in samples of waste plasma obtained after termination of exchange. In blood plasma, cascade filtration was followed by an increase of the mean C3d concentration from 20 to 50 mU/l (p less than 0.001, n = 15), whereas single filtration and centrifugation were followed by a minor decrease. Waste plasma of cascade and single filtration contained 113 +/- 42 mU/exchange (n = 15, mean +/- SD) and 83 +/- 46 mU/exchange (n = 8), respectively. In centrifugation, the concentration of C3d of waste plasma never exceeded that of blood plasma, and the total amount of C3d of waste plasma was only 4 +/- 6 mU/exchange. In contrast to filtration, the centrifugation technique seemed not to be afflicted with any increase in the break down of complement component C3.

Blood Proteins↗
PubMed1988

A capsule-deficient mutant of Francisella tularensis LVS exhibits enhanced sensitivity to killing by serum but diminished sensitivity to killing by polymorphonuclear leukocytes.

The live vaccine strain (LVS) of Francisella tularensis is killed by human polymorphonuclear leukocytes as a result of strictly oxygen-dependent mechanisms (S. Löfgren, A. Tärnvik, M. Thore, and J. Carlsson, Infect. Immun. 43:730-734, 1984). We now report that a capsule-deficient (Cap-) mutant of LVS survives in the leukocytes. In contrast to the encapsulated parent strain, the Cap- mutant was avirulent in mice and was susceptible to the bactericidal effect of nonimmune human serum. The mutant was killed by serum as a result of activation of the classical pathway of complement by naturally occurring immunoglobulin M. This killing by serum was mitigated by the presence of human polymorphonuclear leukocytes. After opsonization in complement component C5-deficient nonimmune serum, the Cap- mutant was ingested and survived in the leukocytes. Under these conditions, the parent strain was killed. The leukocytes responded to both the parent and the Cap- strain with a very low chemiluminescent response. Only the response to the parent strain was inhibited by superoxide dismutase. When the Cap- mutant was opsonized with immunoglobulin G, it induced a higher and superoxide dismutase-inhibitable chemiluminescent response and was killed by the leukocytes. In conclusion, the capsule of F. tularensis LVS seemed to protect this organism against the bactericidal effect of serum. When deprived of the capsule, the organism failed to induce an antimicrobial response in polymorphonuclear leukocytes and survived in the leukocytes. Survival in phagocytes is a key characteristic of intracellular parasites. The Cap- mutant of F. tularensis may become a useful tool in experiments to explain the differences between pathways of ingestion of intracellular parasites, evidenced by the death or survival of the parasite.

Bacterial Proteins↗
PubMed1988

Susceptibility to beta-lactam antibiotics and gentamicin of gram-negative bacilli isolated from hospitalized patients: a Swedish multicenter study.

A total of 952 blood and 1543 urine isolates of gram-negative bacilli from hospitalized patients in 1986-1987 were consecutively collected by 10 Swedish laboratories and tested for susceptibility to 8 beta-lactam antibiotics and to gentamicin. The isolates were mostly Escherichia coli (58% and 44%, respectively) and Klebsiella sp. (17% and 18%). Resistance to ampicillin in blood and urine isolates was found in 35% and 45%, respectively, to piperacillin in 5% and 6%, to cephalothin in 26% and 34%, to cefuroxime in 12% and 22%, to cefotaxime in 3% and 5%, to ceftazidime in 1% and 1%, to imipenem in 0.5% and 0.1%, to aztreonam in 3% and 2%, and to gentamicin in 0.8% and 0%. Resistance of clinically important gram-negative bacilli to new beta-lactam antibiotics and to gentamicin is infrequent in Sweden.

Ampicillin↗
PubMed1987

Immunospecific T-lymphocyte stimulation by membrane proteins from Francisella tularensis.

Membranes from a capsule-deficient mutant of the live-vaccine strain of Francisella tularensis (F. tularensis LVS) were treated with N-lauroyl sarcosinate (Sarkosyl; CIBA-GEIGY Corp., Summit, N.J.). When the Sarkosyl-insoluble fraction was heated in the presence of sodium dodecyl sulfate and mercaptoethanol and subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis, several polypeptides were distinguished. Four major polypeptides were eluted from the gel, each of which stimulated lymphocytes from tularemia-vaccinated individuals but not from nonvaccinated individuals. The stimulation occurred mainly in T lymphocytes. Radioactive labeling of surface proteins of the capsule-deficient bacteria indicated that at least two of the four polypeptides originated from outer membrane proteins. The results suggest that several membrane proteins of F. tularensis LVS induce a specific T-lymphocyte response.

Bacterial Outer Membrane Proteins↗
PubMed1985

Degradation of human immunoglobulins G and M and complement factors C3 and C5 by black-pigmented Bacteroides.

Strains of Bacteroides, Capnocytophaga and Fusobacterium were examined by immunological methods for their ability to degrade the human serum proteins IgG, IgM, C3 and C5. The proteolytic activity of the strains was measured in terms of the breakdown of serum into trichloroacetic acid-soluble material. Only black-pigmented Bacteroides strains showed proteolytic activity. Strains of B. gingivalis degraded IgG, IgM, C3 and C5, strains of B. intermedius IgG and C3, strains of B. endodontalis C3 and IgG and a strain of B. loeschei degraded only IgG. These findings are discussed in relation to the pathogenicity of the black-pigmented Bacteroides.

Bacteroides↗
PubMed1985

Anaerobic phagocytosis, killing, and degradation of Streptococcus pneumoniae by human peripheral blood leukocytes.

Encapsulated Streptococcus pneumoniae of serotypes 2, 9N, 14, 21, and 23F and an unencapsulated variant of type 2 pneumococci were efficiently phagocytosed by both aerobically and anaerobically incubated human leukocytes. In the presence of O2, the pneumococci rapidly lost their viability, whereas during anaerobiosis, killing was considerably delayed. Type 14 pneumococci radiolabeled with [14C]choline or [14C]ethanolamine for cell wall teichoic acid, [14C]uracil for nucleic acids, or [14C]arachidonic acid for unsaturated cytoplasmic membrane lipids were used in studies of the fate of bacterial macromolecules after phagocytosis. The degradation of teichoic acid, RNA, and DNA during anaerobiosis approached that recorded in air at 60 min of incubation (45 to 70% and 55 to 75%, respectively). In contrast, the marked loss of [14C]arachidonic acid from pneumococcal membrane lipids observed in aerobic leukocytes did not occur during anaerobic incubation. Hence, lipid peroxidation could be involved in the rapid aerobic leukocyte killing of pneumococci, whereas a different leukocyte function of as yet unknown nature appears to be responsible for the killing seen in anaerobiosis. Autolysis-resistant type 14 pneumococci were obtained by substituting ethanolamine for choline in a defined culture medium. Differences between such bacteria and normal (autolytic) pneumococci in their killing and degradation by leukocytes were not detected in either the presence or the absence of O2. The aerobic and anaerobic handling of phagocytosed pneumococci by human blood leukocytes thus proceeded independently of the bacterial autolytic system.

Aerobiosis↗
PubMed1985

Long-lasting cell-mediated immunity induced by a live Francisella tularensis vaccine.

The lymphocyte stimulation test was used to estimate specific cell-mediated immunity after vaccination with the live vaccine strain of Francisella tularensis. Nonvaccinated individuals and individuals vaccinated 1, 5 to 6, 7 to 8, and 9 years previously were tested. Lymphocytes from most vaccinees responded to an antigen preparation of the vaccine strain, and those vaccinated 9 years before testing responded to a similar extent as did vaccines in the other groups. A new technique was developed to study the presence of T lymphocytes among the stimulated cells. Stimulated cells were allowed to incorporate [14C]thymidine and were then fractionated into T and non-T lymphocytes. Most of the incorporation appeared in the fraction containing T lymphocytes. The data indicate that cell-mediated immunity endures for at least 9 years after vaccination with the live F. tularensis vaccine.

Antibodies, Bacterial↗
PubMed1984

A wild and an attenuated strain of Francisella tularensis differ in susceptibility to hypochlorous acid: a possible explanation of their different handling by polymorphonuclear leukocytes.

We have previously reported that a wild strain of Francisella tularensis is much less efficiently killed by human polymorphonuclear leukocytes than is an attenuated strain. In the present study, the killing of the attenuated strain was found to be strictly oxygen dependent. The wild and the attenuated strains both induced a respiratory burst in the leukocytes. The difference between the strains in susceptibility to agents produced at the burst could be explained by a difference in susceptibility to hypochlorous acid.

Francisella tularensis↗
PubMed1984

Antigen from Francisella tularensis: nonidentity between determinants participating in cell-mediated and humoral reactions.

After tularemia vaccinations, most individuals respond with cell-mediated and humoral immunity as disclosed by the lymphocyte stimulation test and enzyme-linked immunosorbent assay (ELISA), respectively. There is, however, no correlation between the magnitudes of the two responses, and some individuals show one of the responses only. We now report that the two responses are directed towards different antigenic determinants of the bacterium. Ether-water extraction of the live vaccine strain of Francisella tularensis gave a high yield of material reacting in ELISA as well as in the lymphocyte stimulation test. However, the specificity of the extract was low insofar as it reacted not only with lymphocytes and antibodies of tularemia-vaccinated individuals but also to a fairly high extent with those of nonvaccinated individuals. By using the extract as a starting material, a preparatory procedure was developed, resulting in antigen of high specificity in the two tests. The antigen prepared was a high-molecular-weight, carbohydrate-protein complex. Proteinase K treatment of the antigen abolished the lymphocyte-stimulating activity but did not decrease ELISA activity at all. Periodate treatment, on the other hand, greatly reduced ELISA activity but did not decrease the lymphocyte-stimulating activity. Thus, determinants of F. tularensis responsible for immunospecific lymphocyte stimulation seem to reside in protein, whereas ELISA activity seems to be due mostly to carbohydrate determinants.

Antibody Formation↗
PubMed1983

Oxygen and serum complement in phagocytosis and killing of Propionibacterium acnes.

Phagocytosis and killing of Propionibacterium acnes by human peripheral blood leukocytes were promoted by normal human serum and by serum depleted of immunoglobulin G and M. Serum that had been heat-inactivated, depleted of complement component C3, or depleted of C4 and factor B, did not promote phagocytosis or killing. Depletion of complement-component C4 or factor B from normal human serum did not impair its capacity to promote phagocytosis and killing of P. acnes. These results indicate that phagocytosis of P. acnes is mediated by complement component C3, activated either by the classical or by the alternative pathway. P. acnes was phagocytosed as efficiently under anaerobic as under aerobic conditions. The bacteria were, however, killed at a considerably slower rate by anaerobically incubated leukocytes than by leukocytes incubated in air. Thus, oxygen dependent mechanisms were essential for killing of P. acnes.

Adult↗
PubMed1980

Zinc and immune function in Down's syndrome.

Low levels of zinc in serum and high in blood clots were found in 12 patients with Down's syndrome (DS). They also had an immune deficiency characterized by depressed neutrophil chemotaxis, skin hypersensitivity and lymphocyte responsiveness to PHA in vitro. The patients received zinc sulphate, corresponding to 135 mg Zn++ daily. After treatment for 2 months' serum zinc levels had increased, neutrophil chemotactic responsiveness was normal in 11 of the 12 patients and there were improved lymphocyte responses to high doses of PHA in vitro. Delayed skin reactivity to DNCB was also improved in 10 of 11 patients after zinc therapy. Zinc deficiency may in part explain the increased susceptibility to infection in DS.

Adolescent↗
PubMed1980

Demonstration of opsonizing antibodies to Francisella tularensis by leukocyte chemiluminescence.

Twenty-three individuals were vaccinated with a viable attenuated strain of Francisella tularensis, and blood was collected at various time intervals during 4 weeks. To demonstrate opsonizing antibodies, a mixture of serum and vaccine bacteria was incubated, whereafter the chemiluminescence response of polymorphonuclear (PMN) leukocytes to this mixture was recorded. No opsonizing antibodies against F. tularensis were found in sera obtained before vaccination. Eleven days after vaccination, sera from nine individuals, and 21 days after vaccination, sera from all 23 individuals contained antibodies. Antibodies were demonstrated earlier with the chemiluminescent technique that with the agglutination reaction. Heat treatment (56 degrees C, 30 min) or removal of complement component C3 from immune serum reduced the chemiluminescent response of the leukocytes. A high chemiluminescent response of the leukocytes was induced by immunoglobulin G (IgG)- and IgM-enriched fractions of immune serum in the presence of complement. In the absence of complement, the IgG fraction induced a low chemiluminescent response; the IgM fraction induced no response at all.

Antibodies, Bacterial↗