CIE 11.3 The Adaptive Immune Response (A-level & Osmosis)

Study Notes

The Adaptive Immune Response

Comprised of lymphocytes, a type of white blood cell found in blood and lymphatic systems.
Main types of lymphocytes include T lymphocytes and B lymphocytes, each playing distinct roles in immune response.

T Lymphocytes and Cell-Mediated Immunity

T lymphocytes originate from bone marrow and mature in the thymus.
Clonal deletion eliminates immune cells that react to self-antigens to prevent autoimmune responses.
Clonal anergy occurs when immune cells evade deletion but remain non-functional.

T-Cell Action Steps

Antigen Presentation: Neutrophils and macrophages phagocytose pathogens, acting as antigen-presenting cells (APCs) to T-helper (TH) cells.
TH Cell Activation: Activates pathogen-specific cytotoxic (TC), memory (TM), and B-cells; produces cytokines to proliferate these cells and interferons to enhance immune response.
Cytotoxic T Cells (TC): Directly attacks and kills infected cells through a series of mechanisms.

Mechanism of Cytotoxic T Cells

TC cells target infected cells by binding to MHC molecules.
Produce perforins to create pores in the infected cell’s membrane.
Release granzyme A and B which enter the cell through perforations; A poisons the cell while B destroys it.
Apoptosis is induced when TC’s Fas ligand binds to Fas receptor on the infected cell.
Before apoptosis, the infected cell secretes interferons that inhibit viral replication and bolster defenses in nearby cells.
Antibodies act against remaining viruses after infected cells undergo apoptosis; they opsonize the viruses, blocking their ability to infect new cells.

B Cells and Humoral Immunity

Each B cell is specific to a certain antigen, like T cells.
Activated by interactions with particular TH cells.
B cells produce antibodies critical for humoral immunity, which is defense mediated by secreted molecules in blood and lymph fluid.

Description

Test your knowledge on the adaptive immune response, focusing on the roles of lymphocytes, particularly T and B cells. Explore topics like clonal deletion, antigen presentation, and the action steps of T cells in the immune response.