Full text loading...
Chapter 11 : Immunoglobulin M Determinations
Ebook: Choose a downloadable PDF or ePub file. Chapter is a downloadable PDF file. File must be downloaded within 48 hours of purchase
Since the introduction of the first applications of immunoglobulin M (IgM) determinations in diagnostic virology, a variety of methods have been developed and applied. These methods can generally be separated into three groups: (i) those based on comparing IgM titers before and after chemical inactivation of serum IgM, (ii) those based on the physicochemical separation of IgM from other serum Ig classes, and (iii) those based on solid-phase immunologic detection of IgM antibodies. This chapter discusses the relative merits of each of these approaches. Physicochemical separation methods were originally developed to separate IgM antibodies from other serum Igs to facilitate assay by conventional serological tests, e.g., complement fixation (CF) and hemagglutination inhibition (HI) assays. The major distinguishing features of solid-phase immunoassays are the choice of indicator label and solid phase. Solid-phase immunoassays can be further differentiated into indirect and reverse, or “capture,” forms, based on the orientation of the immunoreactants on the solid phase. The indirect and capture formats have advantages and disadvantages that are described in detail. Compared to the whole virus antigen-based IgM immunoassay, the recombinant protein-based assay offers several distinct advantages. First, the use of infectious virus and special safety precautions used for antigen production are not required. Second, recombinant proteins can be easily standardized and quality controlled. Third, recombinant antigen production is efficient and relatively economical, thus eliminating the generally high production costs associated with virus cultivation.
Primary and secondary immune responses to a hypothetical virus infection. After primary exposure to the viral antigen, there is usually an early and pronounced rise in IgM antibodies, followed by a gradual rise in IgG. IgM antibodies then typically decline to undetectable levels within 1 to 3 months, whereas IgG antibodies can persist for years. Because immunological memory develops, reexposure to the same or similar virus usually results in an early and enhanced rise in IgG antibodies and an attenuated IgM response.
Schema of indirect solid-phase immunoassay for IgM antibody.
Schema of false-positive IgM result caused by RF interference in indirect solid-phase immunoassay.
Schema of reverse, or capture, solid-phase immunoassay for IgM antibody.
Schema of false-positive IgM result caused by RF interference in reverse, or capture, solid-phase immunoassay.
Methods for IgM antibody determination
A selection of commercial vendors of diagnostic kits for virus-specific IgM antibodies