Biology In Human Welfare - Human Health and Disease - Antibodies

• Introduction to Antibodies

  • Antibodies are glycoproteins produced by B-lymphocytes (plasma cells) in response to foreign substances called antigens
  • They are part of the body’s immune system and play a crucial role in defending against pathogens

• Structure of Antibodies

  • Antibodies consist of four polypeptide chains linked together by disulfide bonds
    • Two identical heavy chains and two identical light chains
  • The general structure is similar to Y-shaped molecules
  • The Fab region is the antigen-binding fragment and the Fc region is the crystallizable fragment

• Types of Antibodies

  • IgG: Most abundant antibody in the blood, responsible for long-term immunity
  • IgA: Found in body secretions like saliva, tears, and breast milk, provides localized immunity
  • IgM: First antibody produced during an initial immune response
  • IgE: Involved in allergic reactions, triggers the release of histamine

• Functions of Antibodies

  • Neutralization: Antibodies bind to antigens, preventing them from interacting with host cells
  • Opsonization: Antibodies tag pathogens for destruction by phagocytes
  • Agglutination: Antibodies bind to multiple antigens, forming clumps that can be easily phagocytized
  • Activation of Complement: Antibodies activate the complement system, leading to the destruction of the pathogen

• Antibody-Antigen Interactions

  • Antibodies have specific binding sites that recognize and bind to antigens
  • Antigens are usually proteins or large carbohydrates on the surface of pathogens
  • The binding of antibodies to antigens triggers an immune response

• Production of Antibodies

  • Antibodies are produced in response to the presence of antigens
  • Antigen presentation activates B-lymphocytes, which differentiate into plasma cells
  • Plasma cells secrete antibodies into the bloodstream
  • Memory B-lymphocytes are also formed, providing long-term immunity

• Monoclonal Antibodies

  • Monoclonal antibodies are produced from a single clone of plasma cells
  • They are used for diagnostic tests, targeted drug delivery, and therapeutic purposes
  • Monoclonal antibodies can be produced by hybridoma technology or through genetic engineering

• Applications of Antibodies

  • Immunodiagnostic tests: Antibodies are used to detect the presence of specific antigens or antibodies in patient samples
  • Therapeutic antibodies: Monoclonal antibodies are used for targeted therapy in diseases like cancer and autoimmune disorders
  • Vaccines: Antibodies generated by vaccination provide immunity against specific pathogens

• Antibody-mediated Diseases

  • Autoimmune disorders: Antibodies mistakenly target and attack the body’s own tissues
  • Allergic reactions: IgE antibodies trigger an exaggerated immune response to harmless substances
  • Immunodeficiency disorders: Defects in antibody production or function lead to compromised immune system

11. Classification of Antibodies

• Antibodies are classified based on the type of heavy chain they possess
• IgG, IgA, IgM, IgE, and IgD are the five major classes of antibodies
• Each class has unique properties and functions

12. IgG Antibodies

• IgG antibodies are the most prevalent antibody in the blood
• They can pass through the placenta, providing immunity to the fetus
• IgG antibodies recognize and neutralize pathogens, enhancing phagocytosis

13. IgA Antibodies

• IgA antibodies are found in body secretions such as saliva, tears, and breast milk
• They provide localized immunity, preventing pathogens from entering the body
• IgA antibodies can neutralize pathogens and prevent their attachment to mucosal surfaces

14. IgM Antibodies

• IgM antibodies are the first antibodies produced during an initial immune response
• They are large pentameric molecules that activate complement proteins
• IgM antibodies are involved in agglutination of pathogens

15. IgE Antibodies

• IgE antibodies are associated with allergic reactions and hypersensitivity
• They bind to mast cells and basophils, triggering the release of histamine
• IgE antibodies play a role in protection against parasites

16. Antibody-Antigen Complex Formation

• Antibodies recognize and bind to specific antigens through the variable region of their binding sites
• The specificity of antibody-antigen interactions is determined by complementarity in shape and charge
• The binding affinity can vary, allowing antibodies to target different antigens with different strengths

17. Antibody Production

• Antibodies are produced by plasma cells, which are derived from B-lymphocytes
• B-lymphocytes are activated by antigen presentation and undergo clonal selection
• Memory B-lymphocytes are generated to provide long-term immunity upon re-exposure to the same antigen

18. Hybridoma Technology

• Hybridoma technology is a technique for producing monoclonal antibodies
• It involves fusing antibody-producing plasma cells with immortalized myeloma cells
• The resulting hybrid cells, called hybridomas, can produce large amounts of a specific monoclonal antibody

19. Genetic Engineering of Antibodies

• Antibodies can be genetically engineered to enhance their therapeutic properties
• Techniques such as recombinant DNA technology allow the production of chimeric, humanized, or fully human antibodies
• Genetically engineered antibodies can have improved specificity, reduced immunogenicity, and enhanced stability

20. Applications of Monoclonal Antibodies

• Monoclonal antibodies have revolutionized diagnostics and therapeutics
• They are used in pregnancy tests, HIV tests, and cancer biomarker detection
• Monoclonal antibodies can be conjugated with drugs or toxins for targeted therapy, delivering the agent directly to the affected cells or tissues

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Slide 21

• Therapeutic Applications of Antibodies
  • Antibodies can be used as therapeutic agents for various diseases
  • Monoclonal antibodies have been developed for targeted therapy in cancer
  • Examples include trastuzumab for HER2-positive breast cancer and rituximab for non-Hodgkin lymphoma

Slide 22

• Antibodies in Vaccines
  • Antibodies play a crucial role in vaccine-mediated immunity
  • Vaccination stimulates the production of antibodies against specific antigens
  • Examples of vaccines include the influenza vaccine, hepatitis B vaccine, and human papillomavirus (HPV) vaccine

Slide 23

• Antibodies in Blood Typing
  • Antibodies are used in blood typing tests to determine an individual’s blood group
  • ABO blood groups are classified based on the presence or absence of A and B antigens
  • Antibodies against A and B antigens help identify the blood group of an individual

Slide 24

• Antibodies in Serological Tests
  • Serological tests detect the presence of antibodies or antigens in patient samples
  • Examples of serological tests include ELISA (enzyme-linked immunosorbent assay) and Western blotting
  • These tests are used for the diagnosis of infectious diseases like HIV and hepatitis

Slide 25

• Antibodies in Immunoassays
  • Immunoassays are techniques used to detect and quantify specific molecules
  • Antibodies are used as reagents in immunoassays for detection purposes
  • Examples include pregnancy tests and drug testing kits

Slide 26

• Antibodies in Immunotherapy
  • Immunotherapy uses antibodies to boost the immune system’s ability to fight diseases
  • Immune checkpoint inhibitors like pembrolizumab and nivolumab are used in cancer treatment
  • These antibodies block molecules that suppress the immune response, allowing the immune system to target cancer cells

Slide 27

• Antibodies in Research
  • Antibodies are extensively used in scientific research
  • They are used to study protein expression, localization, and interactions
  • Antibodies are also used in techniques like immunohistochemistry and flow cytometry

Slide 28

• Challenges and Limitations of Antibodies
  • Production of monoclonal antibodies can be time-consuming and costly
  • Antibodies may show cross-reactivity, leading to false positive results
  • Immunogenicity can be a concern, as antibodies can trigger an immune response in some individuals

Slide 29

• Future Directions in Antibody Research
  • Advances in genetic engineering techniques allow the design of novel antibody-based therapeutics
  • Bispecific antibodies, antibody-drug conjugates, and nanobodies are emerging areas of research
  • Antibodies with enhanced specificity and reduced immunogenicity are being developed

Slide 30

• Conclusion
  • Antibodies play a vital role in the body’s immune response against pathogens
  • They are versatile molecules with diverse functions and applications
  • The development of monoclonal antibodies has revolutionized diagnostics and therapeutics in various fields
  • Research in antibody engineering holds promising prospects for the future

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