MICR290_Chapter 16_AFernando AUDIO LECTURE

Overview of Immunity

• Innate Immunity:

  • Inherent capacity of the body to defend against pathogens.

  • Immediate response, generally nonspecific.

• Adaptive Immunity:

  • Acquired ability to recognize and fight specific pathogens.

  • Develops after exposure to antigens and involves memory cells for quicker future responses.

Adaptive Immunity: Key Concepts

• Third Line of Defense:

  • Follows the first (external barriers) and second lines (innate responses).

  • Characterized by its ability to recognize distinct invaders and their products.

• Activation of Adaptive Immunity:

  • Requires prior exposure to specific antigens for activation.

  • Involves lymphocytes (B cells and T cells) that respond specifically to recognized antigens.

Characteristics of Adaptive Immunity

• Specificity:

  • Each immune response targets a specific pathogen.

  • Example: Response to tuberculosis is unique and effective upon second exposure.

• Immunological Memory:

  • Memory cells ensure a faster and more efficient response upon subsequent infections by the same pathogen.

  • Similar to recalling past events in our brain.

• Clonality:

  • Production of many identical cells (clones) that respond to the same antigen.

• Unresponsiveness to Self:

  • The immune system does not attack body's own cells, efficiently differentiating between self and foreign antigens.

Types of Lymphocytes

• B Lymphocytes (B Cells):

  • Mature in the bone marrow, involved in humoral response.

  • Produce antibodies (immunoglobulins) after exposure to antigens.

• T Lymphocytes (T Cells):

  • Mature in the thymus, involved in cell-mediated immunity.

  • Include cytotoxic T cells (kill infected cells), helper T cells (assist other immune cells), and regulatory T cells (maintain immune tolerance).

Immune Responses

• Humoral Immune Response:

  • B cells produce antibodies that bind to pathogens, neutralizing or marking them for destruction.

  • Antibodies can have various functions, including agglutination and opsonization.

• Cell-Mediated Immune Response:

  • T cells directly interact with and kill infected cells or help orchestrate further immune responses.

Antibody Structure and Function

• Antibody Structure:

  • Y-shaped molecules with an antigen-binding site specific to an epitope.

  • Composed of variable and constant regions.

• Functions of Antibodies:

  • Neutralize pathogens, opsonize for phagocytosis, activate complement systems, and facilitate agglutination.

Antigen Processing and Presentation

• Types of Antigens:

  • Exogenous Antigens: From outside the body.

  • Endogenous Antigens: From within, produced by infected cells.

  • Autoantigens: Self-antigens that may trigger autoimmune responses.

• Major Histocompatibility Complex (MHC):

  • Essential for presenting processed antigens to T cells.

  • MHC Class I presents endogenous antigens, MHC Class II presents exogenous antigens.

The Lymphatic System and Immune Response

• Role of the Lymphatic System:

  • Circulates lymph fluid, cleans tissues, and plays a critical role in immune surveillance.

  • Contains lymph nodes, tonsils, and spleen as key secondary lymphoid organs.

Vaccination and Immunization

• Vaccines:

  • Contain killed or attenuated pathogens to trigger an immune response and build memory.

  • Requires initial and booster doses to maintain immunity levels.

• Types of Immunity:

  • Natural Immunity: Acquired through infection.

  • Artificial Immunity: Acquired via vaccination.

  • Both can also be classified as active (body produces antibodies) or passive (acquired antibodies from external sources).

Summary of Important Concepts

• Humoral Response: B cells and antibodies

• Cell-Mediated Response: T cells and their functions

• Memory Cells: Essential for quick immune responses in future exposures

• Clonal Deletion: Mechanism ensuring self-tolerance by eliminating reactive clones during immune response.

ELISA Testing Techniques

• Direct ELISA: Detects presence of specific antigens using enzyme-linked antibodies.

• Sandwich ELISA: Requires both an antibody and an antigen to form a complex recognized by a secondary antibody.

• Indirect ELISA: Utilizes both an antigen and subsequently added antibodies to measure reactions.

Conclusion

• Understanding the adaptive immune response and its components is crucial for grasping how the body defends itself against pathogens effectively.