Practical Applications of Immunology
7. Define specificity.
Many tests based on the interactions of antibodies and antigens have been developed to determine the presence of antibodies or antigens in a patient.
These tests require both specificity and sensitivity of the antibodies. Sensitivity is the ability to recognize and bind to the antigen, specificity is the characteristic of binding only to one antigen and no others.
Hybridomas - produced by the fusion of malignant cells and plasma cells. The resulting population of cells is immortal and able to produce large amounts of a specific antibody.
The interaction of soluble antigens with IgG or IgM antibodies leads to precipitation reactions.
Precipitation reactions depend on the formation of lattices and occur best when antigen and antibody are present in optimal proportions. Excesses of either component decrease lattice formation and subsequent precipitation.
The precipitin ring test is performed in a small tube.
Immunodiffusion procedures are precipitation reactions carried out in an agar gel medium.
Antibody and antigen are loaded in different wells and diffuse through the medium. When the optimal antigen-antibody ratio is reached a visible band appears in the gel.
Immunoelectrophoresis combines electrophoresis with immunodiffusion for the analysis of serum proteins.