Sheep-host polyclonal anti-human IgM. Sheep is one of the four host species in YO Proteins' anti-human IgM family (goat cat. 321, mouse monoclonal cat. 445, rabbit cat. 818, sheep cat. 898) and occupies a specific niche: sandwich-ELISA capture in assays where the detection antibody is goat or mouse. Because sheep and goat IgG separate cleanly from rabbit, mouse and human IgG on standard ProtG/A columns and in cross-adsorbed secondary reagents, a sheep capture / goat detect (or sheep capture / mouse detect) design avoids the most common false-positive failure mode in immunoassays — secondary antibody binding to the capture rather than the analyte.
Sheep antisera also tolerate the higher coating densities used in commercial diagnostic plates, and historically clinical IgM-RF (rheumatoid factor) and infectious-disease IgM serology kits have been built on sheep anti-human IgM backbones for exactly this reason.
Acute-vs-past infection discrimination. The single most important commercial use case for a sheep anti-human IgM capture antibody is kit development for serological tests that must distinguish IgM (acute / recent infection) from IgG (past exposure, vaccine response or established immunity). In these "capture-format" or µ-capture assay designs, cat. 898 is coated on the plate to capture all circulating IgM from the patient sample; antigen-specific IgM is then revealed with a labelled antigen or anti-antigen detection reagent. Because the IgM-capture step is performed before antigen binding, IgG that recognises the same antigen is washed away and cannot generate signal — eliminating the IgG-interference and rheumatoid-factor false positives that plague direct (antigen-immobilised) IgM ELISAs. This is the established assay architecture for early-window diagnosis of dengue, Zika, hepatitis A, measles, rubella, CMV, EBV, Toxoplasma, syphilis, Lyme and recent-onset SARS-CoV-2 — all of which require an acute-phase IgM readout against an *established IgG* background, and all of which depend on a high-titre, low-cross-reactivity sheep-host capture antibody at exactly the position cat. 898 is supplied for. The product is supplied unconjugated for direct use as a capture / coating antibody, or for in-house conjugation when a specific reporter is required.
Specifications
Catalog number: 898
Amount: 1 mg
Host: Sheep
Format: Polyclonal, unconjugated, IgG fraction
Specificity: Human IgM (µ heavy chain)
Applications
- IgM-capture (µ-capture) diagnostic-kit development for acute-vs-past infection discrimination — coat cat. 898 on the plate, capture total IgM from serum, then reveal antigen-specific IgM with labelled antigen or anti-antigen detection. Used by kit developers for dengue, Zika, hepatitis A, measles, rubella, CMV, EBV, Toxoplasma, syphilis, Lyme, parvovirus B19 and recent-onset SARS-CoV-2 acute-phase serology. Eliminates IgG-interference and rheumatoid-factor false positives inherent in direct-format IgM ELISAs.
- Capture antibody in IgM-specific sandwich ELISA — pairs cleanly with goat- or mouse-host detection antibodies on the other side of the sandwich.
- IgM-rheumatoid-factor (IgM-RF) immunoassay development.
- Total-IgM quantification ELISAs for clinical chemistry, nephrology and immunodeficiency workups.
- Capture or precipitation of human IgM from serum, plasma or culture supernatant.
- Coating reagent for IgM-purification affinity columns.
- Western blot primary antibody for human IgM µ chain.
- In-house conjugation to HRP, AP, biotin or fluorophores.
