Adaptive Immunity

Introduction to Adaptive Immunity

Adaptive immunity is the body's highly specific defense mechanism that recognizes and eliminates distinct invaders and their products. Unlike innate immunity, which provides general protection, adaptive immunity tailors its response to specific pathogens and retains memory for faster responses upon re-exposure.

• Specificity: Targets unique antigens found on pathogens.

• Inducibility: Activated only in response to specific antigens.

• Clonality: Generates clones of lymphocytes specific to the antigen.

• Unresponsiveness to self: Normally does not attack the body's own cells.

• Memory: Remembers previous encounters for a faster, stronger response upon re-exposure.

Major Lymphocytes of Adaptive Immunity

Lymphocytes are the primary cells of adaptive immunity, each with specialized roles:

• CD8 T Cell (Cytotoxic T Cell): Directly kills infected or abnormal cells.

• B Cell: Produces antibodies that neutralize pathogens and toxins.

• Regulatory T Cell: Suppresses immune responses to prevent autoimmunity.

• CD4 T Cell (Helper T Cell): Coordinates immune responses by activating B cells and cytotoxic T cells.

Additional info: The cartoon illustration helps visualize the distinct roles of each lymphocyte type.

Comparison of Innate and Adaptive Immunity

Innate and adaptive immunity are two branches of the immune system, each with unique characteristics:

Key Point: Adaptive immunity is more specific and has memory, while innate immunity is immediate and non-specific.

Attributes of Adaptive Immunity

• Specificity: Each lymphocyte recognizes a unique molecular structure (antigen).

• Inducibility: Immune responses are triggered only by exposure to antigens.

• Clonality: Activated lymphocytes proliferate to form clones specific to the antigen.

• Unresponsiveness to self: Mechanisms exist to prevent immune responses against the body's own tissues.

• Memory: After initial exposure, memory cells enable a rapid and robust response to subsequent exposures.

Examples and Applications

• Vaccination: Artificially induces adaptive immunity by exposing the body to harmless forms of antigens, leading to memory cell formation.

• Autoimmune Diseases: Occur when self-tolerance fails and the immune system attacks the body's own tissues.

• Allergies: Result from inappropriate adaptive immune responses to harmless antigens (allergens).

Summary Table: Key Lymphocyte Types

Key Terms

• Antigen: Any molecule recognized as foreign by the immune system, capable of triggering an immune response.

• Epitope: The specific part of an antigen recognized by an antibody or T cell receptor.

• Clonal Selection: The process by which an antigen selectively binds to and activates specific lymphocytes, which then proliferate.

• Memory Cell: A long-lived lymphocyte that responds rapidly upon re-exposure to its specific antigen.