Which unlabeled immune precipitation method in gel is used to quantitate a serum protein?

Which unlabeled immune precipitation method in gel is used to quantitate a serum protein?

• A. Radial immunodiffusion
• B. Double diffusion
• C. Counterimmunoelectrophoresis
• D. Immunofixation electrophoresis

Answer: (A)

The test relies on measuring antigen concentration by the size of a precipitin ring formed in a gel containing antibody, with no labels involved. In radial immunodiffusion, antibody is uniformly distributed in the agar and the serum sample is placed in a well; the antigen diffuses outward and meets the fixed antibody, creating a visible ring when they precipitate. The ring’s radius (or diameter) is proportional to the amount of antigen present, allowing quantitation by comparing to standard curves. This method is specifically unlabeled and designed for estimating serum protein levels such as immunoglobulins. Other gel-based diffusion tests aren’t designed for precise quantitation. Double diffusion is mainly used to assess identity or relatedness of antigens and antibodies and is qualitative in nature. Counterimmunoelectrophoresis speeds up diffusion with an electric field and is used for rapid detection with semi-quantitative interpretation at best. Immunofixation electrophoresis involves applying antisera after electrophoresis and detecting precipitated bands with stains or labels, which identifies and characterizes proteins rather than providing a direct, unlabeled quantitative measurement in a single gel.

The test relies on measuring antigen concentration by the size of a precipitin ring formed in a gel containing antibody, with no labels involved. In radial immunodiffusion, antibody is uniformly distributed in the agar and the serum sample is placed in a well; the antigen diffuses outward and meets the fixed antibody, creating a visible ring when they precipitate. The ring’s radius (or diameter) is proportional to the amount of antigen present, allowing quantitation by comparing to standard curves. This method is specifically unlabeled and designed for estimating serum protein levels such as immunoglobulins.

Other gel-based diffusion tests aren’t designed for precise quantitation. Double diffusion is mainly used to assess identity or relatedness of antigens and antibodies and is qualitative in nature. Counterimmunoelectrophoresis speeds up diffusion with an electric field and is used for rapid detection with semi-quantitative interpretation at best. Immunofixation electrophoresis involves applying antisera after electrophoresis and detecting precipitated bands with stains or labels, which identifies and characterizes proteins rather than providing a direct, unlabeled quantitative measurement in a single gel.