PubMed Health⌕ Search

Biomedical subjects

R Torensma

Publications and source records attributed to R Torensma.

54 records · Page 3Linked to original sources
PubMed1990

Discrimination by rabbit anti-idiotypic antibodies of two murine IgM monoclonal antibodies directed against lipid A.

Two murine IgM monoclonal antibodies (MAs) directed against the lipid A portion of bacterial lipopolysaccharide (LPS) were compared in their binding to Re LPS and lipid A and their idiotypic make-up with rabbit anti-idiotypic sera. Horseradish peroxidase (HRPO)-labelled MAs 8-2 and 26-20 bound equally well to Re LPS. The binding of HRPO-labelled MA 8-2 to synthetic lipid A was low compared to the relatively strong binding of labelled 26-20. The MAs proved to be competitive in a competition binding assay (CBA) with Re LPS as coating antigen. Rabbit immune sera were raised against individual MAs. Anti-idiotypic antibodies (anti-id Abs) were detected with two sensitive enzyme immunoassays (EIA): a solid-phase EIA and an inhibition EIA. The rabbit antisera proved to be idiotype specific, indicating that both MAs recognize separate epitopes. We expect that anti-id Abs will prove to be of value for the differentiation of panels of LPS specific MAs.

Animals↗
PubMed1989

In vitro stimulation of immune spleen cells enhances the number of anti-lipid A-producing hybridomas.

An in vitro stimulation method for the generation of hybridomas producing antibodies with specificity for the weakly immunogenic lipid A is described. Conditions influencing in vitro stimulation of immune spleen cells were investigated. Depending on the experimental conditions the percentage of specific antibody-producing hybridomas varied between 0 and 39%. Most successful was stimulation with both antigen and the synthetic adjuvant muramyl dipeptide (MDP) for 3 days. In vitro stimulation of spleen cells from animals classically immunized with Salmonella Re mutant enhanced the number of lipid A-specific IgG-producing hybridomas from six after direct fusion to 17 after stimulation. These experiments indicate that the synergistic action of antigen and MDP is caused by preferential action on antigen selected B cells.

Animals↗
PubMed1988

Rapid immunodiagnosis of active cytomegalovirus infection by monoclonal antibody staining of blood leucocytes.

The appearance of cytomegalovirus (CMV) antigen positive blood leucocytes (CMV antigenaemia) was investigated in 52 renal transplant recipients during the first three months after transplantation. Using a mixture of three monoclonal antibodies, CMV (immediate early) antigens were detected in cytocentrifuged blood leucocytes within 3-5 h after sampling. The results were related to virus isolation from buffy coats (CMV viraemia), serology with a sensitive enzyme-linked immunosorbent assay (ELISA), and clinical symptoms of CMV disease. The antigen test was positive in all 14 patients with CMV viraemia, in 25 out of 27 of patients with serological evidence of primary or secondary CMV infection, and in 2 out of 25 patients without active infection. In patients with a clinical CMV syndrome the presence of CMV antigen (CMV-Ag) positive blood cells correspond with the period of signs and symptoms. CMV antigens were not detected in 23 out of 25 patients without active infection, nor in healthy controls and patients with other herpesvirus infections. CMV-Ag positive blood cells appeared, on average, nine days before serological signs of active infection. This method provides a rapid and sensitive approach to CMV detection, enabling early clinical diagnosis and subsequent tapering of immunosuppression or commencement of antiviral therapy.

Adult↗
PubMed1988

Comparison between viremia and antigenemia for detection of cytomegalovirus in blood.

In a prospective study, 139 serial blood samples from 15 transplant recipients were assessed for the presence of cytomegalovirus (CMV) by virus isolation (CMV viremia) and by direct staining of CMV antigens (CMV Ag) in blood leukocytes (CMV antigenemia). CMV was isolated from 23 samples, whereas CMV Ag was detected in 44 specimens. All positive samples were from a total of nine patients who were diagnosed as having active CMV infections. In seven patients, active CMV infections were diagnosed by virus isolation from blood and urine and by a significant rise of CMV-specific antibodies. In these patients, 21 of the 23 blood samples which were positive for CMV by cell culture were also positive by direct CMV Ag detection. Moreover, CMV Ag were detected in 23 of the 116 culture-negative samples. Twenty of these samples were from the acute phase of infection in the same seven patients. The remaining three CMV Ag-positive specimens were from the other two patients, from whom CMV was not isolated but who had serological evidence of concomitant active CMV infections. These results suggest that direct detection of CMV Ag in peripheral blood leukocytes is as specific as and more sensitive than current isolation techniques. Furthermore, by its sensitivity and inherent rapidity the antigen detection test proved to be the earliest diagnostic marker of active CMV infection in eight of the nine patients. Finally, it was shown that monoclonal antibodies to CMV immediate early antigens are a prerequisite for demonstration of CMV antigenemia.

Antigens, Viral↗
PubMed1988

Flow cytometric and morphologic studies of HNK1+ (Leu 7+) lymphocytes in relation to cytomegalovirus carrier status.

CMV carrier status of healthy individuals causes a persistent increase in the numbers of lymphocytes expressing the HNK1 (Leu 7) antigen. We investigated this phenomenon by correlating HNK1 fluorescence intensity of the CD3+, CD4+, CD8+ and CD16+ lymphocytes with their morphology. The study was performed on 112 healthy individuals as a function of their CMV carrier status. To this end, the CD3+, CD4+, CD8+ and CD16+ lymphocytes were stratified into subsets with undetectable (-), weak (+) and strong (++) levels of HNK1 fluorescence intensity, as well as into subsets with low, intermediate or high perpendicular light scatter (PLS) signals. Among the CD3+, CD4+ and CD8+ lymphocytes. CMV carrier status was associated with significantly increased numbers of HNK1(+) and particularly HNK1(++) cells. Among the CD16+ lymphocytes, CMV carrier status increased only the HNK1(++) ones significantly. There were clear positive correlations between the PLS characteristics of the CD3+, CD4+, CD8+ and CD16+ lymphocytes and their HNK1 fluorescence intensity. Microscopic analysis of CD3+ lymphocytes sorted into HNK1(-), HNK1(+) and HNK1(++) fractions revealed that the percentage of those cells containing azurophilic granules and the numbers of such granules per cell increased in proportion to their HNK1 fluorescence intensity. Thus, CMV also interacts with the HNK1+ lymphocytes of its healthy carriers by increasing the level of expression of that antigen which is accompanied by increased granularity. Those granular lymphocytes may include cytotoxic cells which are involved in the control of viral replication.

Adolescent↗
PubMed1985

The primary immune response in bronchial asthma. I. A kinetic study of Helix pomatia hemocyanin-specific IgE, IgG, IgA, and IgM antibody responses in patients with asthma and in matched controls.

Eleven asthmatic patients with allergy and 10 age- and sex-matched controls were immunized subcutaneously with 1 mg of the primary test immunogen Helix pomatia hemocyanin (HPH). The HPH-specific IgE, IgG, IgA, and IgM antibody response was measured by ELISA. After immunization, not only the IgE but also the IgG antibody response of the patients exceeded that of the controls (p less than 0.01). IgA antibody response also tended to be higher in the asthmatic group (NS). Except for an earlier rise after immunization in the asthmatic group (p less than 0.05), IgM peak responses did not differ significantly between the two groups. There was a high correlation (r = 0.9) between the magnitude of the IgE and the IgG antibody responses. IgM antibody response did not correlate with the response in any of the other antibody classes measured. The total serum immunoglobulin concentration was determined before immunization. Only the IgE level was significantly higher in the asthmatic group (p less than 0.01). No correlation was found between serum immunoglobulin concentrations and the magnitude of the HPH-specific antibody response in the same class. We conclude that the increased humoral responsiveness of asthmatic patients with allergy is not restricted to the IgE class nor to a limited number of commonly encountered antigens (allergens).

Adult↗
PubMed1985

Lymphadenopathy morphologically consistent with Hodgkin's disease associated with Epstein-Barr virus infection.

This case report describes a case of chronic Epstein-Barr virus infection resulting in lymphadenopathy morphologically indistinguishable from Hodgkin's disease. Morphologic, immunologic, and virologic studies could be performed on three consecutive lymph nodes. For the first time in the literature, Epstein-Barr Nuclear Antigen (EBNA) could be demonstrated in the nuclei of Sternberg-Reed cells.

Aged↗
PubMed1984

HLA phenotype and insulin antibody production.

HLA phenotypes have been determined in 79 patients as part of a prospective study of factors governing the immune response to injected insulin. IgG insulin antibody levels 6 months after starting treatment with bovine insulin were significantly higher in patients bearing HLA-DR7 and this in conjunction with the lack of a similar pattern in the IgG response to Helix pomatia haemocyanin, suggests the presence of an immune response gene for insulin. The hyporesponsiveness of HLA-B8/DR3/C4AQ0 positive individuals is more likely to reflect a non-specific abnormality of immunity.

Adolescent↗
PubMed1983

Oxygen binding by Helix pomatia alpha-haemocyanin studied by X-ray-absorption spectroscopy.

The X-ray absorption spectra of haemocyanin from Helix pomatia were obtained by using X-rays from synchrotron radiation. Cu K-edges were recorded at four conditions, namely fully oxygenated, 85% oxygenated, 12% oxygenated and fully deoxygenated. The percentage oxygenation calculated from the edge-shift of the partially oxygenated samples did not agree with the percentage oxygenation as determined by u.v. measurements. Two intermediates in the oxygenation process are presented to explain the observed dissimilarities.

Animals↗
PubMed1981

Structural and functional aspects of collar domains of Helix pomatia beta c-hemocyanin.

Digestion of beta c-hemocyanin yielded tubular polymers as well as so-called collars. Analysis of the collar fraction revealed that it consisted of two fragments, one having a relative molecular mass of approx. 125000 and the other a relative molecular mass of approx. 65000. They were separated using ion-exchange chromatography. The large fragment dissociated around pH 9.5 into two components having a molecular mass of approx. 65000. Both fragments bound oxygen and displayed heterotropic interactions. The large fragment bound oxygen with a Hill coefficient less than unity under certain conditions. The fragments differed also in amino acid composition, sugar content, spectral parameters, association-dissociation phenomena and ageing. by comparison with fragments obtained after limited proteolysis of tenth molecules, their location in the polypeptide chain was established.

Amino Acids↗
PubMed1981

Reassembly of wall domains of Roman-snail (Helix pomatia) beta-haemocyanin.

beta-Haemocyanin molecules consist of 20 very large polypeptide chains. These chains are composed of eight structural domains. So-called 'collar' domains can be removed by trypsinolysis of the native cylindrical molecule, resulting in an association of the remaining hollow cylinders into large tubular polymers. Dissociation of the tubular polymers gives one single- and four multi-domain fragments. The role of these fragments in the reassembly process of these tubular polymers was investigated. The two-domain fragment could form tubular polymers. The other domain fragments were not able to form tubular polymers unless in the presence of the two-domain fragment. Tubular polymers with enlarged diameter and ribbon-like structures were observed in the reassembly products when the one-domain fragment was omitted.

Animals↗
PubMed1976

Binding of carbon monoxide to alpha-hemocyanin and beta-hemocyanin from Helix pomatia.

The binding of carbon monoxide to alpha and beta-hemocyanin from the snail Helix pomatia was studied under equilibrium conditions. Homotropic interactions upon carbon monoxide binding were much weaker than upon the binding of oxygen. Heterotropic interactions (Bohr effect and calcium-ion effect), however, were just as strong as in the case of the binding of oxygen. For alpha-hemocyanin a linkage has been observed between the binding of carbon monoxide and a change in quaternary structure of the protein.

Animals↗
PubMedDate not supplied

Antigen test for early diagnosis of active cytomegalovirus infection in heart transplant recipients.

An assay was developed for the detection of cytomegalovirus (CMV) antigens in blood leukocytes and evaluated for its diagnostic significance in six heart transplant recipients. Slides of cytocentrifuged blood leukocytes were prepared at regular intervals during the posttransplantation period and stained with CMV-specific monoclonal antibodies, a procedure that took 3 hours. CMV-antigen-positive leukocytes were detected in all five patients with active CMV infection but not in the patient without CMV infection. These CMV-antigen-positive cells were transiently present and first detected 10 to 28 days before there was a significant increase in serum antibody levels. It is concluded that detection of CMV antigens in blood cells is a useful assay for the early diagnosis of active CMV infection in heart transplant recipients.

Adult↗