specific immunity

Specific Immunity Overview

• Introduction to Specific Immunity

  • Definition: Specific immunity refers to the immune response that is tailored to specific pathogens, involving a complex interaction with cells of the immune system.

  • Components: The key components include macrophages, T cells (Helper T and Killer T cells), B cells, and antibodies.

Macrophage Activation and Antigen Processing

• Role of Macrophage

  • Type: Phagocyte.

  • Function: Engulfs antigens, which may include viruses or bacteria.

  • Internal Processing:

    • Contains organelles that secrete enzymes known as lysosomes to break down the antigen.

  • MHC Class II Complex:

    • After processing, the macrophage places a glycoprotein marker on its membrane, known as MHC Class II complex.

    • This marker signals the presence of a potential threat to T cells.

• Chemical Mediators

  • Interleukin-1 (IL-1)

  • Function: Acts as a signaling molecule to recruit helper T cells.

  • Response: Indicates to the immune system that there is an issue requiring a response.

Helper T Cell Activation

• Response to IL-1

  • The helper T cell recognizes the MHC Class II complex on the macrophage.

  • CD4 Marker

    • This T cell is also referred to as a CD4 T cell, indicating its role in assisting the immune response.

• Role of Helper T Cell

  • Monitors the immune response.

  • Identifies the specific virus or antigen causing the infection.

  • Sends out Interleukin-2 (IL-2), a crucial chemical mediator that activates further immune responses.

Pathways of Immune Response

• Overview of the Two Main Pathways

  • Cell Mediated Immunity:

    • Engages with pathogens inside infected cells.

  • Antibody Mediated Immunity:

    • Targets pathogens in extracellular fluid or blood.

Cell Mediated Immunity

• Interleukin-2 Action

  • Stimulates the proliferation of suppressor T cells, killer T cells, and memory T cells.

  • Suppressor T Cells

    • Function: Stop further immune stimulation post-infection.

  • Killer T Cells (Cytotoxic T Cells)

    • Function: Target and destroy virus-infected cells.

    • Mechanism:

    • Infected cells express MHC Class I markers, indicating they are compromised.

    • Killer T cells bind to these markers and release perforin, a chemical that creates pores in the cell membrane, leading to lysis (cell death).

  • Memory T Cells

    • Purpose: Remember the specific virus for quicker response in future infections.

Antibody Mediated Immunity

• Interleukin-2 Action

  • Stimulates proliferation of memory B cells and B cells.

  • B Cells

    • Engages in mitosis, transforming into plasma cells.

    • Plasma cells generate extensive amounts of antibodies targeting specific viruses.

  • Antibodies

    • Y-shaped proteins with two arms specialized to attach to specific antigens.

    • Function in blood and extracellular fluid, representing a proactive defense against free pathogens.

• Three General Functions of Antibodies

  • Neutralization

    • Mechanism: Antibody binding prevents the virus from attaching to host cells.

  • Agglutination

    • Mechanism: Antibodies clump antigens together, making it easier for macrophages to engulf them during phagocytosis.

  • Opsonization

    • Mechanism: Antibody binding enhances phagocytosis by marking the pathogen for destruction, guiding phagocytes to the target.

Complement System and Non-specific Responses

• Enhancement of Non-specific Immune Response

  • IL-2 promotion of complement proteins.

  • Complement Proteins

    • Function: Circulate in blood, identifying and lysing bacterial cells.

  • Macrophages remain alert to clean up debris post-infection following the immune response.

Conclusion

• Recap of Immune Response Components

  • Specific immunity involves a division of labor between cell-mediated and antibody-mediated pathways.

  • Each pathway targets specific aspects of the infection, collaborating to eliminate pathogens and establish immunological memory for faster future responses.