Secreted IgM and complement are important mediators in the optimal initiation of primary T-dependent humoral immune responses. Secreted IgM serves as a natural adjuvant by enhancing the immunogenicity of protein antigens, perhaps as a result of IgM's ability to facilitate antigen deposition onto follicular dendritic cells (FDCs) and promote rapid germinal center (GC) formation. To understand ho...

Binding of host immunoglobulin is a common immune evasion mechanism demonstrated by microbial pathogens. Previous work showed that the malaria parasite Plasmodium falciparum binds the Fc-region of human IgM molecules, resulting in a coating of IgM on the surface of infected erythrocytes. IgM binding is a property of P. falciparum strains showing virulence-related phenotypes such as erythrocyte ...

Three populations of murine splenic B lymphocytes have been characterized previously (6, 7, 9) as those bearing only IgM, those bearing only IgD, and a population bearing both isotopes. These studies were designed to test the response of the IgM+ cells (IgM-only or IgM plus IgD) vs. the IgD-only cells to the B-cell mitogen, lipopolysaccharide. Results that after 1-4 days of culture, in the pres...

Low molecular weight (LMW) IgM is the monomeric subunit of pentameric IgM. It was not found in the sera of 20 healthy subjects but was detected in all six patients with mixed cryoglobulinaemia with a mean value of 1.4 g/l, representing 34% of the total IgM. In three of four patients studied LMW IgM was monoclonal and of the same light chain type (kappa) as the pentameric monoclonal IgM rheumato...

The Meridian ImmunoCard (IC), GenBio ImmunoWELL-IgM, and Remel EIA commercial antibody tests are qualitative enzyme immunoassays that detect antibodies to Mycoplasma pneumoniae in serum. These tests were compared to an M. pneumoniae complement fixation (CF) assay, which uses a commercially available antigen component. The Meridian IC and the ImmunoWELL-IgM detect immunoglobulin M (IgM) only; th...

We review how polyreactive natural IgM autoantibodies (IgM-NAA) protect the host from invading micro-organisms and host neo-antigens that are constantly being produced by oxidation mechanisms and cell apoptosis. Second, we discuss how IgM-NAA and IgM anti-leukocyte antibodies (IgM-ALA) inhibits autoimmune inflammation by anti-idiotypic mechanisms, enhancing removal of apoptotic cells, masking n...

In prior studies, we show that naturally occurring IgM anti-leukocyte autoantibodies (IgM-ALA) bind to CD3, CD4, CCR5, and CXCR4 receptors. These observations prompted us to determine whether IgM-ALA have a role in inhibiting HIV-1 infectivity by inhibiting viral entry into cells. We show that purified IgM, but not IgG, from individual sera of both normal and HIV-1 infected individuals is highl...

Normal mouse IgM is synthesized as hexamers in the absence of J chain and as pentamers in its presence. Previous work has suggested that polymer size is also closely related to formation of the inter-mu chain disulfide bond mediated by cysteine 414, one of three cysteines involved in inter-mu chain bonding. This correlation in turn suggested that formation of C414-C414 might be required for J c...

Hantaan virus is the causative agent of severe hemorrhagic fever with renal syndrome. Clinical surveillance for Hantaan virus infection is unreliable, and laboratory verification is essential. The detection of virus-specific immunoglobulin M (IgM) and IgG in serum is most commonly used for the diagnosis of hantavirus infection. Testing of oral fluid samples instead of serum offers many advantag...

Eighty-seven serum specimens from 20 human subjects experimentally inoculated one or more times with Norwalk virus were quantitatively examined for virus-specific immunoglobulin M (IgM). A sensitive and specific radioimmunoassay for anti-Norwalk virus blocking activity was applied to whole serum and to separate IgM and IgG fractions obtained by sucrose density gradient ultracentrifugation. The ...