3.2.4 Cell recognition and the immune system 2 Flashcards
(42 cards)
The humoral response
-the antibodies involved are soluble in the blood and tissue fluid of the body
The humoral response
Role of B cells/lymphocytes
The humoral response
-produced in primary immune response
-B cell / lymphocyte
└has antibodies on its surface
└which are specific and complementary to only one antigen
-clonal selection
└is the selection and activation of the specific B cell
└by macrophages / antigen presenting cells /T helper cells / cytokines
-clonal expansion
└is where the selected cell divides by mitosis to form clones
-B cells differentiate and specialise
-B cells form plasma cells
└which produce antibodies
└which are, specific and complementary to the antigen
-B cells form memory cells
└memory cells are long-lived and remain in body
└they provide a secondary response
└which is a faster and stronger response to subsequent exposure of same antigen
B cells
- type of white blood cell
- covered with antibodies which are specific and complimentary to different antigens
Clonal selection
-the selection and activation of the specific B cell
└by macrophages / antigen presenting cells /T helper cells / cytokines
Clonal expansion
-where the selected cell divides by mitosis to form clones
Antibody
Definition
-large Y-shaped protein produced by B-cells/plasma cells with antigen-specific receptors
Antibody
Role in immune response (to bacterium/viruses)
-variable region binds to antigen on the surface of the pathogen
└as the variable region specific and complimentary to the antigen
-they agglutinate pathogens
-then immobilise pathogens
-they combine with pathogen to stop entry to cell
-they break wall of bacterium open (lysis)
-the constant region, attracts phagocytes and makes it easier to engulf bacterium
Antibody specificity
–why the antibody will only detect this antigen
- the antibody has a specific primary structure
- and the specific shape of the binding site
- is complimentary to and binds with the antigens (on the pathogen)
- and forms a complex between antibody and antigen
Antibody
Structure
List
Antigen-binding site Light chain Heavy chain Receptor binding site Variable region (different in different antibodies) Constant region
Antibody
Structure
-four polypeptide chains
└one long pair of chains: heavy chains
└one shorted pair of chains: light chains
-each antibody has a specific binding site which fits precisely onto a specific antigen → antigen-antibody complex
└binding site is different on different antibodies so is called a variable region
└sequence of amino acids at binding site form specific 3d shape → binds directly to specific antigen
-the rest of the antibody is known as the constant region which binds to receptors of cells such as b cells
Antibody
Structure to function
-variable region
└= antigen binding site
└the shape of the variable region is specific and complimentary to the antigen= bind to antigen
-hinge region
└allows flexibility
└so it can bind with more than one pathogen
-constant region
└to hold tertiary structure of molecule
└for binding to receptors on cells / phagocytes
-disulphide bonds
└hold polypeptide chains together
How does the antibody lead to the destruction of the antigen?
-don’t destroy them directly
└prepare antigen for destruction
What happens when the antigen is a bacterial cell?
-antibodies assist destruction in 2 ways:
└cause agglutination of the bacterial cells
└=easier for the phagocytes to locate
└serve as markers
└=stimulate phagocytes to engulf bacterial cells they are attached to
Variable region
Function
= antigen binding site
└the shape of the variable region is specific and complimentary to the antigen= bind to antigen
Hinge
Function
-allows flexibility
└so it can bind with more than one pathogen
Constant
Function
-to hold tertiary structure of molecule
└for binding to receptors on cells / phagocytes
Disulphide bonds
Function
-hold polypeptide chains together
The formation of an antigen-antibody complex
-if antigen is specific and complimentary to the antibody
└forms antigen-antibody complex
Agglutination
-as antibodies have 2 binding sites, it can attach to two pathogens at the same time
└they can clump together= agglutination
└=easier for phagocyte to engulf
Agglutination
Issues
-each antibody cam bind to more than one antigen so more than one bacterium
└=agglutination
-an issue as clotting occurs if blood transfusion is not correct
Plasma cells
-secrete antibodies to destroy antigen
└usually into blood plasma
-cells survive for a few days
└make vast quantities
EQ: Suggest three cells where you might expect to find large quantities of plasma cell
Explain why
-rough endoplasmic reticulum
└makes and transport the proteins of the antibodies
-golgi apparatus
└to sort, process and compile the proteins
-mitochondria
└to release the energy needed for such massive antibody production
Memory cells
-responsible for secondary immune response
-live longer than plasma cells (often decades / rest of life)
-circulate blood and tissue fluid
-divide rapidly into plasma cells and more memory cells when they encounter the same antigen
└the plasma cells produce antibodies needed to destroy pathogen
└new memory cells circulate for future infection
-don’t produce antibodies directly
Memory cells
Function
-long-term immunity against the original infection
-increased quantity of antibodies
└produced at faster rate than primary immune response
-ensures new infection is destroyed before it can develop enough to cause harm/symptoms
└the person is often totally unaware that they have been infected
