Enzyme-linked antibodies against CD8 were used to stain the CD8 cells in this preparation of bone marrow using a chromogen. (credit: modification of work by Yamashita M, Fujii Y, Ozaki K, Urano Y, Iwasa M, Nakamura S, Fujii S, Abe M, Sato Y, Yoshino T) OpenStax Microbiology One powerful use of enzyme immunoassays (EIAs) is immunostaining, … Continue reading What is Immunostaining?

This sample of a commercially produced “bedside” card enables quick typing of both a recipient’s and donor’s blood before transfusion. The card contains three reaction sites or wells. One is coated with an anti-A antibody, one with an anti-B antibody, and one with an anti-Rh antibody. Agglutination of red blood cells in a given site … Continue reading Blood Typing and Cross-Matching

Source: OpenStax Microbiology OpenStax Microbiology Agglutination of red blood cells is called hemagglutination. One common assay that uses hemagglutination is the direct Coombs’ test, also called the direct antihuman globulin test (DAT), which generally looks for nonagglutinating antibodies. The test can also detect complement attached to red blood cells. The Coombs’ test is often employed when a newborn … Continue reading The Hemagglutination

Antibodies against six different serovars of Group A strep were attached to latex beads. Each of the six antibody preparations was mixed with bacteria isolated from a patient. The tiny clumps seen in well 4 are indicative of agglutination, which is absent from all other wells. This indicates that the serovar associated with well 4 … Continue reading The Agglutination of Bacteria and Viruses

The complement fixation test is used to determine whether a patient’s serum contains antibodies to a specific antigen. If it does, complement fixation will occur, and there will be no complement available to lyse the antibody-bound sheep red blood cells that are added to the solution in the next step. If the sample does not … Continue reading Complement-Mediated Immunoassay

(a) This diagram summarizes the process of western blotting. Antibodies are used to identify specific bands on the protein gel. (b) A western blot test for antibodies against HIV. The top strip is the negative control; the next strip is the positive control. The bottom two strips are patient serum samples containing antibodies. (credit a: … Continue reading Immunoblot Assay: The Western Blot

(a) This graph shows normal measurements of serum proteins. (b) This photograph shows an immunoelectrophoresis of urine. After electrophoresis, antisera were added to the troughs and the precipitin arcs formed, illustrating the distribution of specific proteins. The skewed arcs (arrows) help to diagnose multiple myeloma. (credit a, b: modification of work by Izawa S, Akimoto … Continue reading The Immunoelectrophoresis

In a neutralization assay, antibodies in patient serum neutralize viruses added to the wells, preventing the formation of plaques. In the assay pictured, the wells with numerous plaques (white patches) contain a low concentration of antibodies. The wells with relatively few plaques have a high concentration of antibodies. (credit: modification of work by Centers for … Continue reading The Neutralization Assay

A precipitin ring test is performed using a standard antigen solution in the bottom of the tube and a serial dilution of antiserum in the top of the tube. Glycerol prevents the two solutions from mixing so that precipitation only occurs at the interface. A visible ring of precipitation is seen in the 1/4, 1/8, … Continue reading The Precipitin Ring Test

Polyclonal antiserum binds to multiple epitopes on an antigen, leading to lattice formation that results in a visible precipitin. Monoclonal antibodies can only bind to a single epitope; therefore, less binding occurs and lattice formation generally does not occur.Source: OpenStax Microbiology OpenStax Microbiology A visible antigen-antibody complex is called a precipitin, and in vitro assays that produce a … Continue reading The Precipitin Reactions