Human Biology · MU Plovdiv

39. Antibodies – structure and function. Immunoglobulin classes and characteristics.

Inside: 25 sections · 4 labelled pictures · 22 flashcards · 18 min

Topic 39 of 66 in the MU Plovdiv syllabus for Human Biology (Dental Medicine, Year 1). The free AceMed note covers it in 25 sections, about 2,392 words (18 min of reading), with 22 flashcards.

In this note

  1. Structure of antibodies
  2. General Characteristics of Antibodies
  3. Formation and Types
  4. Basic Structure: Polypeptide Chains and Overall Shape
  5. Chain Arrangement and Bonding
  6. Domain Architecture
  7. Antigen Binding Regions
  8. Constant Region Functions
  9. Membrane-Bound vs. Soluble Forms
  10. Antibody Isotypes and Their Structural Variations
  11. Oligomeric Forms
  12. Glycosylation and Solubility
  13. Enzymatic Fragmentation and Structural Analysis
  14. Monoclonal Antibodies
  15. MNEMONIC
  16. Functions of antibodies
  17. Understanding the Multifaceted Functions of Antibodies
  18. Direct Functions: Neutralizing and Blocking Threats
  19. Indirect Functions: Enlisting the Innate Immune Army
  20. Complement Activation via the Classical Pathway
  21. Specialized Roles of Different Antibody Classes
  22. Natural Antibodies: Born Ready
  23. When Antibodies Go Wrong: Hypersensitivity Reactions
  24. MNEMONICS
  25. Molecules of cell-mediated immunity.

Structure of antibodies

Structure of Antibodies (Immunoglobulins)

General Characteristics of Antibodies

  • Antibodies, scientifically known as immunoglobulins (Ig), are glycoproteins produced by B lymphocytes.
  • They are central to humoral immunity, the aspect of the immune system that combats pathogens in bodily fluids.
  • The term "Ab" is often used in the context of function (e.g., antigen neutralization), while "Ig" is used to describe structural and classification features.

Formation and Types

  • B cells initially express antibodies as membrane-bound receptors embedded in their plasma membrane.
  • Upon recognizing a specific antigen, the B cell becomes activated and differentiates into a plasma cell, which secretes soluble antibody molecules into the bloodstream.
  • Soluble antibodies retain the same antigen specificity but lack the transmembrane region due to alternative RNA splicing during post-transcriptional processing.

Basic Structure: Polypeptide Chains and Overall Shape

  • Each antibody is a quaternary protein complex consisting of four polypeptide chains:
  • Two identical heavy chains (larger, around 50 kilodaltons)
  • Two identical light chains (smaller, around 25 kilodaltons)
  • These four chains are linked by disulfide bonds, which provide structural integrity.
  • The molecule has a Y-shaped configuration, symmetrical in structure.

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