Adaptive Immune Response Ag & Ab PDF

ADAPTIVE IMMUNE RESPONSE Ag – Ab DR. HUSSEIN (4TH PPT) 1. What is antigenicity? A: The ability to bind an antibody (Ab) or activated T cell. 2. What is immunogenicity? A: The ability to elicit an immune response. 3. What are the four characteristics of an immunogenic...

ADAPTIVE IMMUNE RESPONSE Ag – Ab DR. HUSSEIN (4TH PPT) 1. What is antigenicity? A: The ability to bind an antibody (Ab) or activated T cell. 2. What is immunogenicity? A: The ability to elicit an immune response. 3. What are the four characteristics of an immunogenic molecule? A: Foreignness, high molecular weight, chemical complexity, and degradability. 4. What is a hapten? A: A small molecule that is not immunogenic by itself but becomes immunogenic when combined with a carrier. 5. What are epitopes? A: Immunologically active portions of an antigen recognized by B and T cells. 6. What is the role of MHC molecules? A: To present peptides from protein antigens to T cells. 7. What types of antigens do B lymphocytes recognize independently of T cells? A: Lipopolysaccharides and nucleic acids (DNA and RNA). 8. What antibody is produced in T-cell independent responses? A: IgM, and no memory cells are produced. 9. What is the T-cell dependent antigen recognition route? A: It involves protein antigens, long-term immunity, and production of IgG by class switching. 10. How do dendritic cells present antigens to naive T cells? A: By capturing microbial antigens and migrating to lymph nodes to present them with MHC molecules. 11. What are the properties of antibodies (Abs)? A: They can be membrane-bound or secreted, and their variable regions bind specific antigens. 12. What is the structure of an IgG molecule? A: It consists of two heavy and two light chains with variable and constant regions. 13. What is a polyclonal antibody? A: A heterogeneous mixture of antibodies produced by different B cell clones recognizing various epitopes of an antigen. 14. What is a monoclonal antibody? A: An antibody produced by a single clone of B cells, with identical affinity and specificity. 15. What is the significance of affinity in Ag-Ab interactions? A: It refers to the strength of binding between a single epitope and an antibody. 16. What is avidity in Ag-Ab interactions? A: The overall strength of binding when multiple epitopes interact with multiple antibodies. 17. What are the five classes of antibodies? A: IgG, IgM, IgA, IgD, and IgE. 18. What is the role of IgA? A: It is the main antibody in secretions such as saliva, gut, and respiratory mucus, acting against microbes. 19. What is IgE responsible for? A: Anti-parasitic activity and Type I hypersensitivity reactions (allergies). 20. What is the function of IgD? A: It functions as part of the signaling complex on B cells. 21. What are the four forces involved in Ag-Ab interactions? A: Coulombic (electrostatic), van der Waals forces, hydrogen bonds, and hydrophobic interactions. 22. What is lattice formation in secondary Ag-Ab reactions? A: The aggregation of Ag-Ab complexes resulting in precipitation or agglutination. 23. What is clonal selection? A: The process where a specific B cell is activated by an antigen, leading to its proliferation into memory and plasma cells. 24. What are memory cells? A: B cells that persist after an immune response, providing faster response upon re-exposure to the antigen. 25. What is the role of plasma cells? A: To secrete large amounts of antibodies specific to an antigen. 26. How is antibody diversity generated? A: Through recombination of VDJ gene segments and somatic hypermutation during B cell development. 27. What is class switching in antibodies? A: A process where B cells change the class of antibody they produce (e.g., from IgM to IgG) after antigen exposure. 28. What is affinity maturation? A: The process by which the affinity of antibodies for an antigen increases through repeated exposures. 29. What is the role of the complement system in B cell activation? A: Complement protein C3d binds to antigens and enhances B cell activation by linking to CR2 receptors. 30. What is antibody feedback inhibition? A: Secreted IgG antibodies form immune complexes with antigens, which inhibit further B cell activation via Fc receptors. 31. What is antibody-dependent cellular cytotoxicity (ADCC)? A: A mechanism where antibodies bound to infected cells are recognized by NK cells, leading to cell destruction. 32. How do antibodies neutralize toxins? A: They block the binding of toxins to their target cells, preventing their harmful effects. 33. What is opsonization? A: The process by which antibodies mark pathogens for phagocytosis by immune cells. 34. What is the function of secretory IgA? A: To neutralize pathogens at mucosal surfaces by blocking their entry through the epithelium. 35. What is the humoral immune response? A: The production of antibodies by B cells in response to antigens, leading to pathogen neutralization and destruction. 36. What are the primary and secondary antibody responses? A: The primary response involves naive B cells producing IgM, while the secondary response involves memory B cells producing more IgG with higher affinity. 37. What is the role of MHC class I molecules? A: To present peptides to cytotoxic T cells (CD8+). 38. What is the role of MHC class II molecules? A: To present peptides to helper T cells (CD4+). 39. What is the role of follicular dendritic cells (FDCs)? A: They present antigens to B cells in germinal centers, facilitating the selection of high-affinity B cells. 40. How do microbes evade humoral immunity? A: Through mechanisms such as antigenic variation and inhibiting complement activation.