Paper 11 1. Definition of the terms "affinity", "avidity" and "valency". 2. Agglutination reaction. Definition.Ingredients Mechanism of reaction. Different types of agglutination reaction Definition of the term "titer of agglutinating serum". 3. Classification of techniques of ELISA. 4. What is the basic principle in preparation of live vaccines and who suggested it? What does it mean "attenuated strain "? What are the requirements for vaccine strain used for production of live vaccine? Immunity Vaccines

1. **Definition of the terms "affinity", "avidity" and "valency".**<br /><br /> - **Affinity**: The strength of the interaction between a single antigenic determinant and an individual antibody or receptor. It is a measure of the strength of the bond between a single antigen and a single antibody.<br /> - **Avidity**: The overall strength of binding between an antigen and an antibody, taking into account all the antigenic determinants and the valence of the antibody. It reflects the cumulative strength of multiple interactions between an antigen and an antibody.<br /> - **Valency**: The number of antigenic determinants (epitopes) on an antigen that can interact with a corresponding number of binding sites on an antibody. For antibodies, it refers to the number of antigen-binding sites.<br /><br />2. **Agglutination reaction. Definition. Ingredient: Mechanism of reaction. Different types of agglutination reaction. Definition of the term "titer of agglutinating serum".**<br /><br /> - **Definition**: Agglutination is the clumping of cells or particles, typically caused by antibodies binding to antigens on the surface of the cells or particles.<br /> - **Ingredients**: The main ingredients in an agglutination reaction are the antigen (e.g., cells or particles) and the antibody (e.g., serum containing antibodies).<br /> - **Mechanism of Reaction**: The antibodies bind to specific antigens on the surface of the cells or particles, causing them to clump together. This clumping can be observed microscopically.<br /> - **Different Types of Agglutination Reaction**: <br /> - **Direct Agglutination**: The antigen and antibody are mixed together directly.<br /> - **Indirect Agglutination**: The antigen is coated onto particles (e.g., red blood cells) before the antibody is added.<br /> - **Titer of Agglutinating Serum**: The highest dilution of serum that still causes visible agglutination.<br /><br />3. **Classification of techniques of ELISA.**<br /><br /> - **Direct ELISA**: The antigen is directly labeled with an enzyme.<br /> - **Indirect ELISA**: The antigen is not labeled; instead, an enzyme-labeled secondary antibody is used to detect the primary antibody bound to the antigen.<br /> - **Sandwich ELISA**: The antigen is captured by a solid-phase antibody and then detected with a secondary enzyme-labeled antibody.<br /> - **Competitive ELISA**: The antigen competes with a labeled antigen for binding sites on a solid-phase antibody.<br /><br />4. **What is the basic in preparation of live vaccines and who suggested it? What does it mean "attenuated strain"? What are the requirements for vaccine strain used for production of live vaccine?**<br /><br /> - **Basic in Preparation of Live Vaccines**: The basic principle in the preparation of live vaccines is to use a weakened (attenuated) form of the pathogen that can still stimulate an immune response but does not cause the disease in healthy individuals.<br /> - **Attenuated Strain**: An attenuated strain is a weakened form of a virus or bacterium that has lost its virulence but retains the ability to provoke an immune response.<br /> - **Requirements for Vaccine Strain Used for Production of Live Vaccine**:<br /> - The strain must be stable and consistent in its attenuated state.<br /> - It should be capable of inducing a strong immune response.<br /> - It should not revert to its virulent form.<br /> - It should be free from contaminants and meet safety and efficacy standards.<br /><br />**Immunity Vaccines**: Vaccines that provide immunity against specific pathogens by stimulating the immune system to recognize and fight the pathogen if exposed in the future.