Question

Describe the following:

Coombs tests and the detection of Rhesus incompatibility

Monoclonal Antibodies and Phage display libraries for antibody V-region production

Immunofluorescence microscopy

Immunoprecipitation and Immunoblotting

Use of antibodies in the isolation and identification of genes and their products

Answer 1

A Coombs test (also known as antiglobulin test or AGT) is either of two clinical blood tests used in immunohematology and immunology. The two Coombs tests are the direct Coombs test (DCT, also known as direct antiglobulin test or DAT), and the indirect Coombs test (also known as indirect antiglobulin test or IAT)

The direct Coombs test is used to detect the antibodies or complement proteins that are bound to the surface of red blood cells; a blood sample is taken and the RBCs are washed (removing the patient's own plasma) and then incubated with anti-human globulin (also known as "Coombs reagent"). If this produces agglutination of RBCs, the direct Coombs test is positive, a visual indication that antibodies (and/or complement proteins) are bound to the surface of red blood cells.

The indirect Coombs test is used in prenatal testing of pregnant women and in testing blood prior to a blood transfusion. It detects antibodies against RBCs that are present unbound in the patient's serum. In this case, serum is extracted from the blood sample taken from the patient. Then, the serum is incubated with RBCs of known antigenicity; that is, RBCs with known reference values from other patient blood samples. Finally, anti-human globulin is added. If agglutination occurs, the indirect Coombs test is positive.