PubMed Health⌕ Search

Biomedical subjects

Johan Bjerner

Publications and source records attributed to Johan Bjerner.

7 recordsLinked to original sources
PubMed2005

Use of an in vivo biotinylated single-chain antibody as capture reagent in an immunometric assay to decrease the incidence of interference from heterophilic antibodies.

BACKGROUND: Heterophilic antibodies are a common source of interference in immunometric assays. We tested the hypothesis that the incidence of such interference could be decreased by use of a recombinant in vivo-biotinylated single-chain antibody (scFv) as the capture reagent. METHODS: We established three assays for carcinoembryonic antigen (CEA) with the capture antibody either chemically biotinylated whole monoclonal T84.66 immunoglobulin, a corresponding F(ab')2 fragment, or a site-specifically biotinylated T84.66-derived single-chain antibody (scFv). Antibodies were attached to streptavidin-coated microplates. A common europium-labeled anti-CEA tracer monoclonal antibody was used. The F(ab')2 assay used a buffer that contained bovine immunoglobulin and aggregated irrelevant monoclonal antibody MAK33 as blocking agents. The whole T84.66 immunoglobulin and scFv assays were performed without addition of blocking agents. From a previous study of 11 261 sera, we tested 390 samples that had displayed heterophilic antibody interference and 179 samples that had not. RESULTS: After correction for bias and analytical variation [2.56 x SD (from the precision profile)], 383 samples displayed significantly different values (>1 microg/L) in the whole T84.66-based assay and the F(ab')2 assay. In contrast, only nine samples showed falsely high CEA concentrations in the scFv assay. After blocking agents were added to the assay buffer, eight of the nine samples displayed results equivalent to those of the F(ab')2 assay, and sample dilution produced equivalent results for the remaining sample. CONCLUSION: Their ability to be site-specifically biotinylated and their relative resistance to heterophilic antibody interference indicate that single-chain antibodies may be useful solid-phase reagents in immunometric assays.

Animals↗
PubMed2005

Human heterophilic antibodies display specificity for murine IgG subclasses.

OBJECTIVES: The study investigated heterophilic antibodies: the human immunoglobulin classes involved and their specificity for different murine IgG subclasses. DESIGN AND METHODS: Using immunofluorometric assays for human IgA, IgM and IgG binding murine IgG1, we analyzed 173 samples displaying positive interference and 97 negative control samples from a previous study. We also set up assays for heterophilic antibody interference using Mabs from different murine IgG subclasses. Three Mabs each of murine IgG1, IgG2a and IgG2b subclasses, one murine IgG3 Mab and one rat Mab were used. RESULTS: Elevated levels of human murine IgG1-binding immunoglobulins of IgM class only were found in 40% of interference-positive samples, human IgG only in 1.7%, and human IgA only in 2.3% of the samples. Both elevated human IgG and IgM classes were found in 3.5% of the samples, IgA and IgM in 4.0%, and finally, all three immunoglobulin classes in 1.7% of the samples. Eighty percent of interference positive samples showed heterophilic assay interference for at least one murine IgG1 Mab, 35% for IgG2a, 66% for IgG2b, 52% for IgG3a and 17% for the rat Mab. CONCLUSIONS: Heterophilic antibody interference is mainly caused by IgM class human antibodies with a marked murine IgG subclass specificity. Combining assay antibodies from different murine IgG subclasses may reduce interference in immunoassays.

Animals↗
PubMed2004

Testing and validating a homogeneous immunometric assay for interference.

We analyzed 95 sera, demonstrating interference in a previous study, with the Kryptor homogeneous time-resolved fluorescence resonance energy transfer carcinoembryonic antigen (CEA) immunoassay (Brahms AG, Berlin, Germany). Only one serum differed, i.e., 6.0 microg/l for Kryptor vs. 13.3 microg/l for a microtiter plate in-house immunofluorometric assay (IFMA), using both aggregated mouse immunoglobulins as blocker and capture monoclonal antibody (Mab) F(ab')2-fragments to reduce interference. Sera were further analyzed with experimental IFMAs with intact capture Mabs and without blocker. The Kryptor-CEA assay Mab GFR44 (capture) had elevated results in 71% of sera with the Kryptor Mab G15 (tracer) or in 81% with our tracer Mab. G15 (capture) had 65% elevated results with GFR44 (tracer) or 99% with our tracer Mab. The latter was reduced from 99% to 62% by adding Kryptor blocker to the buffer or to 30% by adding our blocker. Finally, combining both assay Mabs and assay buffer from Kryptor still gave interference in 16% of sera. Kryptor-CEA assay results thus agreed with our in-house CEA assay results, showing no interference. As the Kryptor-CEA assay antibodies were sensitive to interference and the Kryptor-CEA assay buffer did not reduce interference as efficiently as our in-house assay buffer, the Kryptor-CEA assay format was crucial for the absence of interference.

Animals↗
PubMed2002

Immunometric assay interference: incidence and prevention.

BACKGROUND: The primary aim of the study was to reduce interference in an in-house two-site, two-step immunometric assay. METHODS: In the running laboratory routine, 11 261 samples were tested with a carcinoembryonic antigen (CEA) assay with bovine immunoglobulin but no murine immunoglobulins in the buffer, in parallel to our routine CEA assay, using 15 mg/L heat-treated nonspecific murine immunoglobulin (MAK33) in the buffer and with the Fc fragments removed from the capture antibody. RESULTS: The frequency of interference was estimated to be 4.0% (95% confidence interval, 3.3-4.7%). The addition of 15 mg/L native MAK33 had little effect (frequency, 3.9%; 95% confidence interval, 3.2-4.6%), whereas adding 15 mg/L heat-treated MAK33 reduced interference to 0.86% (0.61-1.12%), and adding 50 mg/L reduced it further to 0.06% (0-0.13%). Removing the Fc fragments by itself reduced interference to 0.10% (0.02-0.19%). There were no statistically significant differences for age (P <0.23) or gender (P <0.40) between patients with interference (n = 210) and a randomly selected interference-negative control group (n = 186). Interference was not constant in patients: 15 of 25 individuals positive for interference and with four or more samples screened for interference had an interference-negative sample either before or after the peak of interference. CONCLUSIONS: In a two-site, two-step immunometric assay using mouse monoclonal antibodies, use of heat-treated nonspecific murine immunoglobulin in the buffer or removal of the Fc fragment from the capture antibody could improve performance.

Animals↗
PubMedDate not supplied

Serum levels of soluble transferrin receptor correlate with severity of disease but not with iron stores in patients with malignant lymphomas.

Soluble transferrin receptor levels in serum (s-sTfR) may be useful in differentiating between iron deficiency anemia and anemia of chronic disease. However, there is both theoretical and clinical evidence for elevated s-sTfR levels in patients with various hematological malignancies. In the present study, routine bone marrow aspirations were performed in 82 patients with malignant lymphomas (63 with non-Hodgkin's lymphoma and 19 with Hodgkin's disease). Smears were stained for evaluation of iron stores and graded. Patients were also given a disease score based on bone marrow morphology, erythrocyte sedimentation rate and LDH. s-sTfR levels correlated better with disease score [partial Spearman rank correlation coefficient (r(s)) controlled for iron stores was 0.51 (95% confidence interval 0.39-0.65); p < 0.001] than with iron stores [partial r(s) controlled for disease score was -0.25 (95% confidence interval -0.44 to -0.03); p = 0.027]. This study showed elevated s-sTfR levels in patients with malignant lymphomas without any signs of iron deficiency anemia. The diagnosis of iron deficiency anemia should not be established upon the basis of s-sTfR alone in this group of patients.

Adult↗
PubMedDate not supplied

MUC1 serum assays in breast cancer: tumor specificities and reference levels.

The aim of the study was to establish reference ranges and to explore the tumor specificities of two automated assays for MUC1. Sera from 124 female blood donors, 144 patients with benign disease of the breast, 69 patients with stage I, 75 with stage II, 89 with stage III and 38 patients with stage IV breast cancer were analyzed for MUC1 levels using two automated immunometric assays employing assay antibody pairs Ma695/Ma552 and BC2/GP1.4, respectively. All subjects were female. The Ma695/Ma552 assay yielded means of 13.86 (SD 6.55) kU/l for blood donors, 15.98 (SD 8.31) kU/l for benign disease, 15.83 (SD 7.92) kU/l for stage I, 15.01 (SD 8.03) kU/l for stage II, 33.80 (SD 66.53) kU/l for stage III and 469.22 (SD 906.61) kU/l for stage IV breast cancer. The BC2/GP1.4 assay gave means of 12.00 (SD 6.41) kU/l for blood donors, 14.68 (SD 9.33) kU/l for benign disease, 14.13 (SD 8.12) kU/l for stage I, 12.10 (SD 6.61) kU/l for stage II, 19.80 (SD 29.05) kU/l for stage III and 191.04 (SD 527.16) kU/l for stage IV breast cancer. Patients with benign diseases of the breast had slightly higher values than female blood donors with both assays leading to correspondingly different reference ranges. The Ma695/Ma552 assay had higher specificity for tumor MUC1 than the BC2/GP1.4 assay for all stages, and the study thus confirms the differences in tumor specificity for MUC1 assays.

Adult↗