Unit 8.2: Adaptive Immunity - Third line of Defense

What is the difference between the primary immune response and secondary immune response?

The primary immune response takes some time for immune cells to respond, but on the secondary immune response the response is much quicker and more intense

What is the secondary response specific to?

The secondary response is specific to a particular antigen

What is an epitope?

An epitope is a specific part of an antigen where an antibody can bind to

What are haptens?

Haptens are molecules that are too small to be noticed by the immune system

• Example of hapten: Penicillin

What do haptens attach to and what do they become?

What do stem cells eventually mature into?

Half of the stem cells stay in the bone marrow to mature into B cells

The other half of stem cells migrate to the thymus to mature into T cells

Where does cellular immunity take place and which type of cell does it involve?

Cellular immunity takes place inside the body’s cells and it involves T-lymphocytes (T-cells)

Where does humoral immunity take place and which type of cell does it involve?

Humoral immunity takes place in plasma and interstitial spaces and it involves B-lymphocytes (B-cells)

Which cells are part of cellular immunity’s defenses?

1. Antigen-presenting cells: macrophages, dendritic cells

2. T cells: helper T cells, cytotoxic T cells, memory T cells

Which cells are targetted by the cellular immunity system?

Abnormal body cells such as cancer or infected cells

Presentation of helper T cells

What is the role/purpose of MHC-II?

MHC-II reveals a pathogen’s antigens to helper T-cells in order to activate the immune response

Helper T cell diagram activation

What are the three steps required for an inactive helper T cell to be activated?

1. Macrophage presents an antigen on MHC-II

2. Helper T-cell receptor recognizes the antigen and CD4 binds to MHC-II

3. Cytokines activate the helper T-cell

Which two cells do activated helper T-cells divide into?

1. Specialized helper T cells which release cytokines

   1. These cytokines activate cytotoxic T cells, activate B cells and enhance innate immunity

2. Memory helper T cells

What are the three steps required for an inactive cytotoxic T cell to be activated?

1. Infected cell presents an antigen on MHC-I

2. Cytotoxic T-cell receptor recognizes the antigen and CD8 binds to MHC-I

3. Cytokines activate the cytotoxic t-cell

Which two cells do activated cytotoxic T cells divide into?

1. Specialized cytotoxic T cells that release perforin and granzymes

2. Memory cytotoxic T cells

Which cells are part of humoral immunity’s defense?

1. Activated helper T cells

2. B cells

3. Antibodies

Which cells are humoral immunity's targets?

• Free or extracellular antigens

Describe antibodies’ structure

The antibody is a Y shaped defensive protein where it contains two ‘arms’ that contain binding sites for the antigen of pathogens

Which antibody class is this?

Which antibody class is this?

Which antibody class is this?

What are the 5 ways antibodies protect us from pathogens?

1. Neutralization

2. Agglutination

3. Opsonization

4. Antibody-dependent cell mediated cytotoxicity

5. Complement activation - cell lysis

Describe the process of how B cells activate without helper T cells

1. Antigen directly activates the B cell

2. PAMPs activate the B cell through TLRs

3. B cell becomes a plasma cell and secretes antibodies

Describe the process of how B cells activate with helper T cells

1. Antigen binds to B cell

2. B cell takes in the antigen

3. B cell presents antigen to helper T cell

4. Helper T cell recognizes it, releasing cytokines

5. B cell becomes a plasma cell and secretes antibodies

What two cells do B cells differentiate into after being activated?

1. Plasma cells

2. Memory B cells

Which cells are involved in cellular immunity and their functions?

1. Helper T cell: secretes cytokines

2. Cytotoxic T cell: produces perforin and granzyme proteins

Which cells are involved in humoral immunity and their functions?

1. B cells: defends against pathogens using antibodies