Humoral and Cell mediated responses Flashcards
What is the immune response?
It is a homeostatic mechanism.
What are the 2 responses of the immune response/system?
- Humoral response/antibody-mediated immunity
- Cell-mediated response
What does the Humoral response/antibody-mediated immunty produce
B cells/B lymphocytes
What does the cell-mediated response produce?
T cells/T lymphocytes
Where are lymphocytes produced?
Lymphocytes a reproduced in the bone marrow. Some mature in the bone marrow and are called B cells. T cells mature in the thymus.
Where are lymphocytes stored?
Lymphoid tissue
Define what an antigen is
An antigen is a substance capable of causing an immune response.
What are 3 examples of an antigen?
- Virus particles
- Toxins
- Pollen
What are self-antigens?
Self-antigens bind to self receptors on the T cell, causing the T cell not to destroy it as it recognises it as a part of the body.
What are non-self antigens?
Non-self antigens bind to non-self receptors on T cells and are destroyed by them.
Define what an antibody is
Antibodies are Y-shaped proteins that belong to a group of proteins called immunoglobulins. They contain active sites that have a specific shape and combine with a complimentary antigen.
What are the 5 types of antibodies?
- Immunoglobins A
- Immunoglobins D
- Immunoglobins E
- Immunoglobins B
- Immunoglobins M
What are antigen-presenting cells (APC’s)?
APCs are immune cells that detect, engulf and inform the immune response about an infection.
What are 3 examples of APCs?
- Dendritic cells
- Macrophages
- B cells
What is the molecule that attaches to the APC?
Major Histocompatibility Complex Class II (MHC II)
What is Major histocompatibility complex class II?
MHC is a molecule that bonds to the antigen and displays it on the surface of the cell.
What is antibody-mediated immunity?
Provides resistance to pathogens and toxins before they enter the cell.
Outline the steps of antibody-mediated immunity
- APC presents the antigen to a specific B-cell and T-cell helper cells
- The APC and T helper cells release cytokines which activate more B cells
- Activated B cells undergo mitosis.
- Most B cells become plasma cells and secrete antibodies to circulate in the blood, lymph and extracellular fluid.
- Antibodies combine with specific antigens to form an antigen-antibody complex and destroy inactive non-self antigens.
- The remaining clones become memory cells which circulate all tissues in case of reinfection.
How do antibodies work?
- Inacatviate foreign enzymes or toxins by inhibiting their reaction with other cells
- Bind to the surface of viruses and prevent them from entering
- Coat bacteria with a substance so that phagocytes more easily consume them
- Cause particles to undergo agglutination assisting phagocytes in consuming them
- dissolve organisms
- React with soluble substances to make them insoluble and more easily consumed by phagocytes
What are memory cells?
A type of cell that recognises antigens to which the body has previously been exposed.
Describe memory cell’s primary and secondary immune responses
The primary response is slower as the body must undergo the process of antibody mediated immunity. The secondary response is much faster due to memory cells recognising the antigen more quickly.
What is cell-mediated immunity?
Provides immunity after the pathogen has entered the cell.
Outline the steps of cell-mediated immunity
- Pathogen is engulfed by macrophages and lysozymes destroy it and the APC presents the antigen on the surface
- Help T cells only recognise antigens bound to MHC II
- CYtokines are released by macrophages and helper T cells
- Cytokines stimulate T cells to form clones. They are sensitised, enlarged and divide.
- Most T cells become killer T cells or helper T cells and migrate to the place where large numbers of antigens are resent. Some become memory cells
- Cytokines attract macrophages
- Killer T cells release cytokines that cause the death of infected cells
What do killer T cells do?
Killer T cells attach to antigens and destroy them.
