When carrier particles are coated with an antigen of interest and the carrier particles are not normally found in living things, this type of reaction is called?

• A. Direct agglutination reaction.
• B. Reverse agglutination reaction.
• C. Passive agglutination reaction. 
• D. Foreign agglutination reaction.

Answer: (C)

Verified step by step guidance

1. Understand the concept of agglutination reactions, which involve the clumping of particles due to antigen-antibody interactions.
2. Recognize that in a direct agglutination reaction, the antigen is naturally present on the surface of the carrier particles (such as red blood cells or bacteria).
3. Note that in passive agglutination reactions, the antigen is artificially attached (coated) onto carrier particles that are not normally found in living organisms, such as latex beads.
4. Identify that when carrier particles are coated with an antigen of interest and these particles are foreign to living systems, the reaction is termed a passive agglutination reaction.
5. Conclude that this method is useful for detecting antibodies or antigens by observing the clumping of these coated particles in the presence of specific antibodies.