Lecture on Antibodies

Introduction

• Focus on antibodies in the immune system.
• Previous lecture covered B lymphocytes and primary immune response.

Role of B Lymphocytes

• Pathogens cause sickness during the primary immune response.
• B lymphocytes, upon stimulation, undergo clonal expansion.
• Clonal expansion results in the formation of plasma cells.
• Plasma cells produce and release antibodies.
• Antibodies bind to antigens, aiding in recovery from infection.

Antibodies vs. Antibiotics

• Antibodies: Proteins produced by the immune system to neutralize pathogens.
• Antibiotics: Medications used to kill bacteria.

Structure of Antibodies

• Quarternary Globular Glycoproteins:
  • Protein made of amino acids (peptide bonds).
  • Globular shape due to water solubility.
  • Quarternary structure involves more than one polypeptide chain.
  • Glycoproteins are proteins attached to sugars.
• Four Polypeptide Chains:
  • Two heavy (long) chains and two light (short) chains.
  • Chains linked by disulfide bridges (strong covalent bonds).

Functional Regions of Antibodies

• Antigen Binding Site: Area where antibodies attach to antigens.
• Constant Region: Identical amino acid sequence across different antibodies.
• Variable Region: Differing amino acid sequences to bind to specific antigens.

Antibody Functionality

How Antibodies Combat Pathogens:

1. Virus Neutralization:

   • Bind to viral antigens, preventing cell infection and replication.

2. Bacterial Slowing:

   • Attach to bacterial flagella, slowing movement for phagocytosis.

3. Toxin Neutralization:

   • Bind to toxins, preventing cellular damage.

4. Pathogen Clumping:

   • Clump together, hindering movement and aiding phagocytosis.
   • Enabled by hinge region flexibility.

5. Opsonization:

   • Enhance phagocytosis by binding to phagocyte receptors.

Conclusion

• Antibodies play a crucial role in defending against infections.
• They neutralize viruses, slow bacteria, neutralize toxins, clump pathogens, and enhance phagocytosis.
• Effective recovery from infections involves these antibody-mediated processes.