PubMed · 389482
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P Garcia-Webb, A Bonser. 1979-07-02. Decrease in measured C-peptide immunoreactivity on storage.. https://doi.org/10.1016/0009-8981(79)90347-4
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The one-step sandwich immunoassay is increasingly replacing the traditional two-step immunoassay due to obvious advantages such as assay speed. However, the one-step sandwich immunoassay suffers from the 'hook' effect irrespective of the analyte characteristics. The 'hook' effect is dependent primarily on the analyte concentration. Three different model analytes, human growth hormone (hGH), the dimeric form of hGH (D-hGH, having a discrete number of repeating epitopes) and ferritin (multiple epitopes) having different immunological properties have been employed in studies of the one-step sandwich immunoassay. The characteristics of each of the model analytes offer new insights into general guidelines for assay procedures. These guidelines permit rapid optimization of assay conditions for an immunoassay without a priori knowledge of the immunological characteristics of the antibody or antigen. Both experimental and theoretical data show several instances where high capacity solid-phase antibodies can effectively shift the 'hook' to relatively higher analyte concentrations. The effect of the concentration of labeled antibody on assay response was examined theoretically.
In vivo treatment with anti-CD4 antibody profoundly suppresses a number of T cell-dependent responses and is clinically useful in the treatment of certain mouse models of autoimmune disease. Treatment with anti-CD4 antibody will inactivate and can deplete CD4 T cells, but the mechanisms responsible for these effects are incompletely understood. When mouse spleen cells were exposed in vitro to both SRBC and monoclonal anti-CD4, there was 55% reduction of the anti-SRBC response. If cultures were preincubated with anti-CD4 for 48 h before in vitro challenge, the reduction was greater than 80%. When unfractionated spleen cells were cultured with anti-CD4 for 96 h, there was actual elimination of CD4 cells in these cultures since virtually all CD3+ cells were CD8+. Activation of T cells by exposure to anti-CD3 rendered them resistant to antibody-mediated CD4 depletion. This resistance to CD4 depletion was seen even in cultures that were pretreated with anti-CD4 for as long as 24 h before anti-CD3 exposure. In cultures of purified T cells, anti-CD4 did not eliminate CD4 T cells. However, culture of T cells with macrophage-rich adherent cells and anti-CD4 resulted in elimination of CD4 T cells. Thus, it appears that macrophages play a role in anti-CD4-induced T cell elimination. While anti-CD4 did not eliminate CD4 cells from a population of purified T cells, there was profound down-regulation of cell surface CD4. Activating T cells with immobilized anti-CD3 before addition of anti-CD4 prevented down-regulation of CD4. These experiments demonstrate that T cell activation by anti-CD3 renders the activated cells resistant to antibody-induced CD4 down-regulation and to antibody-induced CD4 T cell depletion. These findings may have relevance to the application of anti-CD4 therapy in human diseases that are mediated by activated Th cells.
Recent clinical observations support the hypothesis that persistent parvovirus B19 is a triggering factor of rheumatoid arthritis (RA) in certain genetically predisposed individuals. If this hypothesis is correct, a number of RA patients may exhibit parvovirus B19 DNA in their synovial membranes. We tested the synovial tissue and peripheral blood leukocytes of 20 patients with RA, 24 patients with other arthritides or osteoarthritis (non-RA), and 34 healthy blood donors for the presence of parvovirus B19 DNA using specific DNA amplification by polymerase chain reaction (PCR). Using this technique, parvovirus B19 DNA was demonstrated in the synovial biopsies of 75% of patients with RA but in those of only 16.7% of patients with non-RA. In autologous peripheral blood mononuclear cells the percentage of PCR-positive patients was about 15% in both RA and non-RA groups and did not differ from that in healthy controls. When the PCR data were correlated with the presence of anti-parvovirus B19 IgG antibodies in serum and synovia all patients with parvovirus B19 DNA in peripheral blood alone or in both peripheral blood and synovial membrane were seropositive. In contrast, about 40% of patients with parvovirus B19 DNA restricted to the synovial membrane were seronegative. These data indicate a highly disease-related persistence of parvovirus B19 in the rheumatoid synovium.