Immunological Techniques Quiz

Immunological Techniques

• Immunological techniques are methods used to study the immune system and its components.
• Antibody immobilization involves capturing antibodies (capture antibodies) and using a secondary antibody for detection.
• Antigen-antibody reactions are based on non-covalent bonds, including hydrogen bonds, electrostatic bonds, van der Waals forces, and hydrophobic bonds.
• Multiple bonds contribute to strong binding, despite the individual bonds being weak.
• The binding is reversible.
• High-affinity interactions are stronger than low-affinity interactions.
• Avidity describes the overall strength of antigen-antibody binding, considering the number of binding sites.
• Specificity refers to an antibody's ability to exclusively recognize a single antigenic determinant.
• Cross-reactivity occurs when an antibody reacts with similar or shared epitopes on different antigens.
• Factors Affecting Ag/Ab Reactions include the antigen antibody ratio and the physical form of the antigen (soluble or particulate).
• Soluble antigens can remain in solution, or precipitate if the concentration is high enough.
• Particulate antigens, such as blood cells or viruses, can form visible aggregates through agglutination when combining with antibodies.
• Equivalence describes the optimal antigen-antibody ratio where visible lattice formation (precipitation) results.

Types of Antibodies

• Monoclonal antibodies are a homogenous population produced by a single clone of plasma B cells, recognizing a particular epitope on a specific antigen. They are commonly used for therapies and are adaptable for diverse applications.
• Polyclonal antibodies are a heterogeneous population produced by different clones of plasma B cells, recognizing different epitopes on a particular antigen. They are useful for detection, but the results may vary between samples due to diverse production.

Tests Based on Antigen-Antibody Reactions

• These tests can detect either antigens or antibodies.
• Qualitative tests measure the presence or absence of agglutination.
• Quantitative tests measure the concentration of antigens or antibodies (titers).
• Agglutination and Hemagglutination tests detect clumping of particles (or cells, like red blood cells).
• Passive agglutination involves coating soluble antigens onto particles for antibody detection.
• Coombs tests (direct and indirect) detect antibodies or complement proteins attached to red blood cells.
• Agglutination inhibition tests are used to detect the presence of viruses or antiviral antibodies.

Precipitation Tests

• Precipitation tests involve the formation of visible precipitates in solution or gel matrices.
• Equivalence is the zone of optimal antigen and antibody proportions for maximal precipitation formation.
• Radial Immunodiffusion (RID) is a quantitative method using antigens and antibodies in an agarose gel to measure antigen concentration.
• Immunoelectrophoresis combines electrophoresis and immunodiffusion to analyze complex antigen mixtures.
• Countercurrent electrophoresis allows the detection of antigen-antibody reactions with different charge antigens.

Radioimmunoassays (RIAs)

• Competitive RIAs use unlabeled antigens to compete with radiolabeled antigens for antibody binding.
• Non-competitive RIAs measure the amount of labeled antibody bound to immobilised antigens.

Enzyme-Linked Immunosorbent Assays (ELISAs)

• ELISAs use enzyme-conjugated secondary antibodies for detecting antigens and antibodies.
• Direct ELISA, Indirect ELISA, Sandwich ELISA, and Competitive ELISA are different variations of this test.

Western Blotting (Immunoblotting)

• Western blotting combines electrophoresis and immunoassays to detect specific proteins.

Immunochromatography

• Immunochromatography uses lateral flow and a conjugate pad for antigen-antibody interaction and colored particle migration to detect antigens.
• A control line ensures the test is functioning correctly.