Biomedical subjects

R Carlsson

Publications and source records attributed to R Carlsson.

At least 55 records · Page 3Linked to original sources

PubMed1995

Antigen-specific activation of B cells in vitro after recruitment of T cell help with superantigen.

BACKGROUND: Human B cells can proliferate in vitro after stimulation with anti-Ig and via the CD40 molecule. Superantigens like SEA which bind to MHC class II antigens on, e.g. B cells can polyclonally activate T cells via interaction with their TcR. The activated T cell subsequently activates the B cells to proliferation and Ig-production. OBJECTIVES: To investigate whether superantigen could be used to direct polyclonal T cell help to human B cells stimulated by antigen in a restricted manner resulting in production of antigen-specific antibodies in vitro. STUDY DESIGN: Purified B cells were preincubated with the antigen in manners allowing crosslinking of surface-Ig. The antigen exposed B cells were then cultured together with autologous CD4+ helper T cells and in the presence of various concentrations of SEA. Antibody production was measured by ELISA after 7-12 days of culture. RESULTS: Antigen-specific activation of B cells could be obtained after stimulating the B cells with antigen or anti-surface-Ig antibodies in the presence of T helper cells and SEA. The degree of B cell activation (proliferation as well as antibody production) depended on the dose of antigen as well as on the dose of SEA used. Increased crosslinking of surface-Ig on antigen-specific B cells enhanced Ig production. Specific antibody production to a secondary recall antigen (tetanus toxoid) and to primary antigens (DNP and GM2) were obtained. The specific B cell response was dependent on contact between T and B cells. CONCLUSION: the results obtained demonstrate that the superantigen SEA can recruit T cell help to human B cells specifically stimulated by antigens, resulting in production of antigen reactive antibodies in vitro.

Animals↗

PubMed1995

Stimulation of human peripheral lymphocytes via CD3 and soluble antigen abrogates specific antibody production by reducing memory B cell numbers.

Human B cells are polyclonally activated in vitro by T cells stimulated with immobilized anti-CD3 monoclonal antibodies. We have analysed the effect of CD3 ligation on the production of antigen-specific antibodies, using peripheral blood lymphocytes from tetanus toxoid vaccinated blood donors. High levels of antigen-specific antibodies were obtained after stimulation with anti-CD3 antibodies for 7 days. Addition of soluble recall antigen did not affect the total amount of Ig produced, but dramatically decreased the antigen-specific response. The addition of IL-2, IL-4, and anti-CD40 or anti-CD28 antibodies or the removal of antigen did not restore the B cell response. Analysis using limiting dilution of B cells showed that the frequency of antigen-specific memory B cells decreased significantly in cultures stimulated with antigen. The antigen-specific B cell response could be completely restored only if the soluble antigen was cross-linked on the surface of the B cells. These results suggested that peripheral memory B cells were eliminated or anergized in the presence of soluble antigen.

Antibody Formation↗

PubMed1995

Serum lipids four weeks after acute myocardial infarction are a valid basis for lipid lowering intervention in patients receiving thrombolysis.

OBJECTIVE: To compare serum concentrations of total cholesterol, low density lipoprotein (LDL) cholesterol, high density lipoprotein (HDL) cholesterol, and triglycerides four weeks after acute myocardial infarction with baseline levels measured within 24 hours after onset of symptoms. DESIGN: A prospective study including 141 patients with acute myocardial infarction who were admitted to the coronary care unit at a general hospital. MEASUREMENTS: Fasting serum concentrations of total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides. MAIN RESULTS: In patients receiving thrombolytic therapy, no significant differences were found in serum lipids four weeks after admission compared to values estimated within 24 hours from onset of symptoms. In patients not receiving thrombolytic therapy, total cholesterol and low density lipoprotein cholesterol showed a minor increase four weeks after admission compared to values obtained within 24 hours after onset of symptoms. High density lipoprotein cholesterol and triglycerides remained unchanged. CONCLUSIONS: In patients with acute myocardial infarction receiving thrombolytic therapy, serum lipids measured four weeks after onset of infarction are reasonably valid estimates of baseline lipid levels and may be used to decide about lipid lowering interventions. This information can be a basis for actions against hyperlipidaemia early after hospital discharge when the patient is highly motivated to change lifestyles and is still in close contact with a cardiologist or other physician.

Adult↗

PubMed1995

[Need for a long-term program in the follow-up of anti-lipid treatment following coronary artery surgery?].

The positive effects of cholesterol-lowering therapy in coronary artery disease are well recognised. This study, on 99 consecutive coronary artery bypass grafted patients, shows that an intensive one-year follow-up at a secondary prevention specialist clinic significantly improves cholesterol levels compared to conventional follow-up in the primary health care system. However, these positive results are not consistent after a 2.6 year return to the primary health care. Consequently, improved collaboration between hospital and primary health care physicians in the development of structured secondary prevention programmes is essential.

Adult↗

PubMed1995

Enhancement of specific immunoglobulin production in SCID-hu-PBL mice after in vitro priming of human B cells with superantigen.

Priming of human mature B cells in vitro with staphylococcal enterotoxin A (SEA) prior to transplantation of the B cells into severe combined immunodeficiency (SCID) mice, together with human T-helper cells, resulted in higher and more uniform concentrations of serum IgG in the mice. This indicated that a large number of B cells had become activated, which was supported by the finding that SEA priming resulted in production of immunoglobulin displaying a more normal kappa/lambda ratio than was obtained in the absence of SEA priming. However, IgM concentrations were not affected by SEA priming. Immunization of mice, transplanted with SEA-primed B cells, with both primary and secondary antigens resulted in a high specific IgG response to both types of antigen. The elevated levels of specific antibodies were not merely the consequence of an unspecific stimulation of B cells caused by SEA, as the ratio of specific antibody to total IgG was much higher in animals receiving SEA-primed B cells. Thus, a co-operative effect on immunoglobulin production of stimulating B cells via surface immunoglobulin and help delivered by SEA-activated T-helper cells was indicated. A specific antigen-dependent IgM response to a secondary antigen was observed as well, but was, in contrast to the IgG response, not influenced by SEA priming of B cells. No IgM antibodies with reactivities to the primary antigens were detected in the SCID sera at any time-point after immunization. The results thus indicate that SEA might replace T-cell epitopes in antigens and efficiently recruit an abundance of T-cell help to B cells, resulting in enhanced production of specific IgG antibodies.

Animals↗

PubMed1995

Induction of primary antigen-specific immune reponses in SCID-hu-PBL by coupled T-B epitopes.

Adoptive transfer of human lymphoid cells into immunodeficient (SCID) mice lacking the ability to functionally rearrange T- and B-cell receptor genes constitutes a unique model to study and manipulate human immunocytes. We have investigated this model for the purpose of generating an antigen-specific primary humoral immune response. Peripheral blood lymphocytes (PBL) derived from blood donors were used to repopulate SCID mice, which subsequently were immunized with different B-cell epitopes coupled to either tetanus toxoid (TT), or to a promiscuous helper epitope of TT, or by incorporating the antigens into a liposome construct. By recruiting the necessary T-cell help found in the T-cell memory compartment against TT, primary immune responses were obtained against the hapten dinitrophenyl (DNP), the V3 loop peptide derived from glycoprotein (gp120) (HIV-1), the melanoma-associated GD2 ganglioside and ovine submaxillary mucin. The primary immune response against the GD2 ganglioside was induced by incapsulating TT into GD2-containing liposomes. These liposome constructs also allowed us to induce a high human IgG serotitre (3000-4000) against this normally not very immunogenic ganglioside.

Animals↗

PubMed1995

Omeprazole and H2-receptor antagonists in the acute treatment of duodenal ulcer, gastric ulcer and reflux oesophagitis: a meta-analysis.

This paper is a meta-analysis of 30 published, double-blind clinical trials comparing omeprazole with ranitidine or cimetidine for the treatment of duodenal ulcer, gastric ulcer and reflux oesophagitis. These studies compare the recommended doses of omeprazole with those for ranitidine and cimetidine, and the confidence intervals for the therapeutic gain show that the findings are highly reliable. The difference in healing rates favoured omeprazole over ranitidine in patients with duodenal ulcer after 2 weeks of treatment (15.2 percentage units; P < 0.001), and after 4 weeks of treatment in patients with gastric ulcer (9.9 percentage units; P = 0.005), or reflux oesophagitis (23 percentage units; P < 0.001). Similarly, omeprazole gave a 20.6 percentage units higher average healing rate than cimetidine in patients with duodenal ulcer after 2 weeks of treatment (P < 0.0001). Significantly more patients treated with omeprazole were free of symptoms at their first follow-up visit than patients treated with ranitidine or cimetidine.

Adult↗

PubMed1994

Activation of human CD4+45RA+ T cells using B cells as accessory cells.

Human naive CD4+ T cells, as defined by expression of CD45RA and lack of CD45R0, can be activated in vitro using B cells as accessory cells. CD4+CD45RA+ T cells proliferate, as determined by [3H]thymidine or bromodeoxyuridine (BrdU) incorporation, after activation with the superantigen staphylococcal enterotoxin A (SEA) presented by major histocompatibility complex class II-expressing B cells. The identity of the responding cells as being CD45RA+ and not contaminating CD45R0+ T cells was determined by FACS analysis, showing that purified CD45RA-expressing T-helper cells went into S phase and progressively acquired expression of the CD45R0 isoform while simultaneously losing expression of the CD45RA isoform. Cultivation of the CD4+ T-cell subsets under limiting dilution conditions supported these findings and revealed that (i) the frequency of responding cells in the CD45RA+ population was equal to or higher than in the CD45R0+ subset and (ii) that the number of CD45R0+ cells possibly contaminating the CD45RA population was too low to be able to account for the response observed.

Antigen-Presenting Cells↗

PubMed1994

Human Th0-type T helper-cell clone supports antigen-specific immunoglobulin production in scid/beige-hu mice.

Tetanus toxoid-specific T cells have been generated from human splenic lymphocytes by an initial 6-day stimulation period with antigen, followed by a proliferation period with recombinant IL-2 and human feeder cells. Proliferating T cells were subsequently cloned by limiting dilution. A human T-cell clone that was functionally characterized showed: (i) a specific proliferative response to tetanus toxoid in the presence of autologous Epstein-Barr virus (EBV)-transformed lymphoblastoid cells; (ii) a phenotype characteristic for the helper/inducer CD4+/CD8-/CD450R0+ T cells, and (iii) a lymphokine profile, as determined by mRNA analysis, representative of Th0-like human CD4+ T helper cells. This tetanus toxoid-specific T-cell clone which showed antigen-dependent helper activity for antibody production by autologous B cells in vitro could also provide T-cell help to antigen-specific human B cells transplanted into severe combined immunodeficiency (scid/beige) mice.

Aged↗

PubMed1994

Antigen-specific human immunoglobulin production in SCID mice transplanted with human peripheral lymphocytes is dependent on CD4+ CD45RO+ T cells.

Severe combined immunodeficient (SCID) mice, lacking mature T and B cells and virtually devoid of endogenous serum immunoglobulins, spontaneously produce large amounts of human immunoglobulin after transplantation with human peripheral blood lymphocytes (PBL). Moreover, after immunization with antigen an active immune response resulting in a production of specific antibodies can be induced. Here we report that human T cells must be co-transplanted with B cells into the SCID mice for immunoglobulin production to occur. Resting human B cells could be activated to immunoglobulin production in the absence of human monocytes and a specific antibody response to tetanus toxoid (TT) could be induced, suggesting that the human B cells could present antigen to T cells in the SCID environment. Production of human immunoglobulins, as well as specific antibodies, was obtained only if CD4+ T cells of the memory phenotype, i.e. expressing CD45RO, were present. No human immunoglobulin, either of IgM or of IgG isotype, was found in SCID sera if mice were co-transplanted with human B cells and CD45RA expressing CD4+ T cells. However, FACS analysis revealed that the transplanted CD45RA+ cells became activated and differentiated towards CD45RO+ cells within 1-2 weeks. These cells also gained the lymphokine gene expression pattern associated with CD45RO+ cells, as demonstrated by polymerase chain reaction (PCR) analysis, and could support immunoglobulin production in SCID mice transplanted with fresh B cells. In fact, after differentiation of CD4+ CD45RA+ T cells towards expression of CD45RO, either in vivo in the SCID mouse or in vitro, these cells could interact with and activate human B cells to immunoglobulin production. Furthermore, in vitro activated and differentiated CD4+ CD45RA+ T cells from vaccinated donors were also able to support production of TT-specific antibodies provided the antigen was administered.

Animals↗

PubMed1993

Low-dose warfarin decreases coagulability without affecting prothrombin complex activity.

OBJECTIVES: To assess the efficacy of a fixed, low dose of warfarin in lowering factor VII coagulant activity (FVII:C) and to investigate the effects on the plasma coagulation cascade. DESIGN: An open pilot study with two dose levels of warfarin: 1.25 and 2.5 mg day-1 during two consecutive 4-week periods. All subjects received aspirin 75 mg day-1. Prothrombin fragment 1 + 2 (F(1 + 2)), protein C, protein S, FVII:C, factor X and P-prothrombin complex activity (P-PT) were measured at baseline, at 2-week intervals and 4 weeks after end of treatment. Coagulation activation peptide F(1 + 2) was used as a marker of thrombin formation. SUBJECTS: Twelve male patients with a history of myocardial infarction. Inclusion was made through a written questionnaire. RESULTS: Warfarin 1.25 mg day-1 lowered FVII:C from 113 U dl-1 to 107 U dl-1 (P = 0.025) and F(1 + 2) from 1.60 nmol l-1 to 1.27 nmol l-1 (P = 0.013) but had no effect on protein C or P-PT. A dose of 2.5 mg day-1 induced further lowering of FVII:C (91 U dl-1, P = 0.0042), and also of protein C from 116% to 99% (P = 0.034) and P-PT from 107% to 81% (P = 0.0096) mean values. CONCLUSION: Warfarin 1.25 mg day-1 seems to exert an anticoagulant effect without reduction in PT or the natural anticoagulant protein C and is suggested, in combination with aspirin, to be a safe and simple therapy against arterial thrombotic disease, making regular PT controls unnecessary.

Adult↗

PubMed1992

Human peripheral blood lymphocytes transplanted into SCID mice constitute an in vivo culture system exhibiting several parameters found in a normal humoral immune response and are a source of immunocytes for the production of human monoclonal antibodies.

Human PBL from vaccinated healthy blood donors, which was transplanted i.p. into mice with severe combined immunodeficiency (SCID), exhibited an Ag-dependent humoral Ir against tetanus toxoid. This Ir was dose dependent and was completely abrogated by immunizing with large amounts of Ag, suggesting a high dose tolerization of the B cells. A dose-dependent selection of specific, high affinity B clonotypes was also suggested, since immunization with low concentrations of tetanus toxoid produced antisera with higher avidity than immunizations using a high dose of Ag. The production of human Ig and the clonal outgrowth of normal human B cells in the SCID mouse was strongly down-regulated by human NK cells. Human immune B lymphocytes were also recovered from immunized SCID mice and transformed with EBV, yielding lymphoblastoid cell lines producing high affinity antitetanus human IgG antibodies. These results suggest that SCID mice, repopulated with human PBL, can constitute a functional model of several parameters of a normal human humoral Ir and can provide a source of immune B cells for the production of human mAb.

Animals↗

PubMed1992

Epstein-Barr virus-induced transformation of human B lymphocytes: the effect of L-leucyl-L-leucine methyl ester on inhibitory T cell populations.

Epstein-Barr virus-mediated transformation of human B lymphocytes is inhibited by human T lymphocytes as well as by interferon-gamma. Removal of the inhibitory cell populations is essential in order to achieve successful transformation in vitro. Cells with the capacity to inhibit outgrowth of lymphoblastoid cell lines can be removed by pretreatment of peripheral blood mononuclear cells with L-leucyl-L-leucine methyl ester. This treatment eliminates monocytes, NK-cells and a CD8+ T cell subpopulation. We now show that such treatment also has toxic effects on other human T cell populations. In addition, CD4+ and/or CD8+ lymphocytes are demonstrated to contain effector cell activities which inhibit outgrowth of EBV-transformed B cells. This inhibitory activity is abolished after treatment of peripheral blood mononuclear cells or purified CD4+ T cells with L-leucyl-L-leucine methyl ester. No evidence was found for a selective toxicity against any subset within the CD4+ or CD8+ T cell populations. However, the capacity of the treated cells, both peripheral blood mononuclear cells and purified CD4+ T lymphocytes, to produce mRNA encoding IFN-gamma, a protein previously shown to downregulate outgrowth of EBV-transformed B cells, was selectively impaired. The results obtained suggest a role for CD4+ T cells to inhibit EBV-induced transformation of B cells.

Antibodies, Monoclonal↗

PubMed1992

Gastric endocrine cells and gastritis in patients receiving long-term omeprazole treatment.

Both argyrophil endocrine cells and gastritis were investigated in 2,120 biopsies of gastric corpus mucosa from 443 out of 448 patients receiving long-term (for periods ranging from several months to 4 years) omeprazole treatment. None of the patients showed neoplasia or dysplasia, either endocrine or non-endocrine. In 123 out of 443 patients (27.8%), endocrine hyperplasia of diffuse (9.3%), linear (4.1%) or micronodular (14.4%) type was detected either before or at some time during treatment. Chronic atrophic gastritis was found in 45 (10.2%) patients, 60% of whom also showed micronodular hyperplasia. In patients with chronic atrophic gastritis, micronodular hyperplasia occurred in 49% of 96 biopsies, compared with 6% of 1,083 biopsies from patients with non-atrophic chronic gastritis and 2% of 941 biopsies from patients with no evidence of gastritis. In 202 patients treated with omeprazole for at least 330 days, the incidence of micronodular hyperplasia increased from 2.5% at the first biopsy to 10.4% at the final biopsy, while the incidence of chronic atrophic gastritis increased from 1.0% to 13.0%. The present and parallel studies suggest that progression of gastritis is inherent in the natural history of acid-related diseases, while endocrine cell changes are mostly secondary to gastritis-related gland atrophy and have no tumorigenic potential.

Adult↗

PubMed1992

Human CD4+ T cells expressing CD45RA acquire the lymphokine gene expression of CD45RO+ T-helper cells after activation in vitro.

CD4+ T cells were separated into subpopulations according to their expression of different isoforms of the CD45R molecule, i.e. CD45RA and CD45RO. The separated cells were activated with staphylococcal enterotoxin A (SEA) in the presence of formalin fixed Raji cells. Each set of cells was activated twice with a 6-day interval, and the lymphokine gene expression during the first 3 days after initiation of each stimulation was followed by use of polymerase chain reaction (PCR) technology. The lymphokine messenger RNA (mRNA) profiles were found to differ between the subsets, since after the first stimulation the CD45RA+ cells produced mRNA encoding interleukin-2 (IL-2) and IL-1 alpha, whereas the CD45RO+ cells transcribed genes for IL-1 alpha, IL-2, IL-4, IL-5 and interferon-gamma (IFN-gamma). After 6 days of SEA stimulation both populations were mainly CD45RO reactive, and when restimulated displayed the lymphokine mRNA profile restricted to this subset. These results indicate that the CD45RA subset is a precursor of the CD45RO and further strengthen the hypothesis that the former cell population represents naive whereas the latter subset represents memory T cells within the CD4 subset.

Antigens, CD↗

PubMed1991

Human monoclonal antibodies with different fine specificity for digoxin derivatives: cloning of heavy and light chain variable region sequences.

Human-mouse hybridoma cell lines producing human monoclonal antibodies against the cardiac glycoside digoxin were established after in vitro immunization or direct immortalization of human peripheral blood lymphocytes with digoxin. Three antibodies, designated MO6, LH92 and LH1114, displayed different patterns of fine specificity against digoxin and several digoxin analogues, as elucidated by inhibition ELISA. All three monoclonal antibodies had mu heavy chains, two of them (MO6 and LH114) had kappa light chains and one (LH92) lambda light chains. DNA encoding the variable regions of both heavy and light chains of the three antibodies were amplified from cDNA using the polymerase chain reaction (PCR). The nucleotide sequences of the amplified DNA were determined after subcloning of PCR fragments in M13 vectors. The deduced amino acid sequences revealed considerable sequence differences in the complementarity determining regions between the three antibodies.

Amino Acid Sequence↗

PubMed1990

The TcR-CD3 complex is required for activation of human lymphocytes with staphylococcal enterotoxin A.

The involvement of the T-cell receptor (TcR)-CD3 complex in activation of human mononuclear cells by staphylococcal enterotoxin A (SEA) was investigated. TcR-CD3 molecular complex expression was modulated with monoclonal anti-CD3 antibodies. The proliferative response of such modulated cells to optimal doses of phytohaemagglutinin and monoclonal anti-CD3 antibodies and to suboptimal doses of SEA was greatly impaired. In concentrations above 1 ng/ml, SEA could also activate the modulated cells to a certain extent, apparently due to reexpression of low levels of the TcR-CD3 molecular complex during incubation. TcR-CD3 modulation decreased the ability of SEA-activated cells to produce interleukin 2 and gamma interferon. Analysis of cloned cells revealed that SEA could only activate CD3+ but not CD3- clones. Both CD4+ and CD8+ clones were activated. The results show that SEA activates human T cells by a mechanism involving the TcR-CD3 molecular complex.

Antibodies, Monoclonal↗

PubMed1990

Phenotypical and functional differentiation of CD4+ CD45RA+ human T cells following polyclonal activation.

Human CD4+ T cells differ in their expression of the leucocyte common antigen. Antibodies detecting certain forms (CD45RA and CD45RO) of this antigen have been used to identify and isolate subpopulations of the CD4+ T cells. These isolated subsets have been shown to have different abilities concerning lymphokine production and provision of help to B cells for Ig production. When these T-cell subsets were activated in vitro with polyclonal activators, the production. When these T-cell subsets were activated in vitro with polyclonal activators, the CD45RA+ cells lost this marker and gained the expression of CD45RO. This was true for all mitogens used in this report, i.e. accessory cell-dependent stimulation with SEA and accessory cell-independent activation with PMA or PHA. A correlation between proliferation and differentiation was observed, but this was probably not causative as stimulation with PMA in the absence of DNA synthesis resulted in the acquisition of CD45RO and loss of the CD45RA antigen. Moreover, cells proliferating vigorously for long periods of time expressed both markers at significant levels, which suggests that proliferation did not automatically result in complete loss of the CD45RA marker. The phenotypical differentiation was associated with a functional differentiation which induced the stimulated cells' ability to act as helper cells for Ig production and to produce gamma interferon (IFN-gamma). The results obtained in this study support the contention that the CD45RA+ cells are precursors of the CD45RO+ cells and that the two subsets represent different maturational stages of the same lineage.

Antigens, Differentiation↗