Specific Immune Responses Flashcards
What type of white blood cells make up the specific immune response?
Lymphocytes make up the specific immune response.
What are the positives and negatives of lymphocytes?
Lymphocytes can target a specific pathogen
But they are much slower to act than the non-specific response
What are the 2 main types of response that the specific response features to pathogens?
The humoral response
The cellular response
Define what is meant by humoral response?
The humoral response - this is the response that targets pathogens in body fluid with antibodies
The cellular response - this is the response which involves highly-specialised cells that target pathogens inside cells
What is cell signalling?
The specific immune response involves a coordinated response between a wide range of cells.
In order to work together effectively, these cells need to communicate.
This is known as cell signalling.
How is cell signalling achieved in cells?
Cell signalling - is achieved through cell surface molecules
And through the release of hormone-like chemicals called cytokines
What must the target cell have in order to detect a signal?
In order to detect a signal, the target cell must have a specific cell surface receptor that is complementary to the cell surface molecule or chemical.
What are the ways in which the specific immune response can be initiated?
1) The ‘Pathogen’ itself
2) infected body cells
3) antigen presentation
4) hormone-like chemicals
What does an invading pathogen have which act as a marker, which is then detected by our body cells and cells of the immune response?
An invading pathogen has foreign antigens. These foreign antigens act as flags or markers that say ‘I am foreign’ and therefore these can be detected by our body cells and cells of the immune response
How are infected body cells involved in initiating a specific immune response?
- infected body cells are involved in sending out ‘distress signals’
What does a body cell do once infected?
When a body cell is infected, the internal cell organelles such as lysosomes will attempt to fight the pathogen
As a result a number of pathogen cells can become damaged and parts can then often end up attached to the plasma membrane
What functions does the fact that some of the pathogen can end up attached to the plasma membrane have?
Pathogen parts attached to infected body cells can act as a distress signal and be detected by cells from the immune system
It can also act as a marker to indicate that the host cell is infected - T killer cells (a specialised WBC which will be explained later) can recognise this and can destroy it
Identify the type of phagocyte which take antigen-presentation to the next level?
Macrophages in the lymph nodes - play an important role in initiating the specific response to a disease
Explain how a macrophage becomes an antigen presenting cell?
- When a phagocyte engulfs a pathogen it incorporates part of the pathogen onto its cell surface
- It then becomes known as an antigen-presenting cell. An antigen-presenting cells is meant to activate the cells of the specific immune response that can ‘combat’ the pathogen more effectively
What is the name of the hormone-like chemicals that are released by cells which can act as instructions to many of the cells of the immune response?
Cytokines - act as instructions to many of the cells of the immune response
What are monokines?
Monokines - these are released by macrophages. Monokines are cytokines which attract nearby neutrophils by chemotaxis
What is chemotaxis?
Attraction by chemicals
What are interleukins?
These are released by macrophages
These are cytokines which can stimulate the proliferations and differentiations of the specific immune system such as B and T cells
What is proliferation?
Dividing of cells to increase numbers
Define lymphocytes:
Lymphocytes are relatively small WBC
They circulate around the body in the BLOOD and the LYMPH
They are the WBC involved in the specific immune response
Name the two main types of lymphocytes?
- T-lymphocyte
2. B-lymphocyte
Where are T-lymphocytes and B-lymphocytes produced?
Bone marrow
Where do T-lymphocytes mature?
THYMUS
Where do B-lymphocytes mature?
BONE MARROW
Once both types of lymphocytes are mature they reside in various locations in the body, but especially which location?
Especially high numbers can be observed within the lymph nodes
What do lymphocytes produce as they mature?
As they mature lymphocytes produce small quantities of a particular glycoprotein called antibodies.
When antibodies are placed onto the plasma membrane of lymphocytes what do they act as?
The antibodies act as receptor which are able to bind with a particular antigen, if this should appear in the body.
What happens if pathogens do enter the body and the lymphocytes have receptor that are complementary to the antigen on the pathogen?
Then a response is triggered and B-lymphocytes and T-lymphocyte respond in different ways.
What type of lymphocytes are involved in the cell mediated response?
T-LYMPHOCYTE are involved in the cell-mediated response because they do not involve antibodies but target and story cells that are directly infected by pathogens.
What is the first step that initiates the T-lymphocyte?
Stp 1:
An antigen-presenting cell macrophage, ingests, processes and presents the antigen on its cell surface membrane
This is known as antigen-presentations
Step 2 - T-lymphocyte
The antigen-presenting cell then travels through the lymphatic system until it comes in contact with a T-lymphocytes that has an antibody on its surface which is COMPLEMENTARY to this antigen.
Once a particular antigen is recognised by a specific T-lymphocyte it becomes selected
CLONAL selection
What is clonal selection?
Once a particular antigen is recognised by a specific T-lymphocyte it becomes selected - clonal selection
Step 3 - T-lymphocytes
Once activate the selected T-cell beings to divide by mitosis and differentiate
This is known as clonal expansion
What are the main 2 types of T-lymphocytes?
T-killer
T-helper
What is the role of a T-killer lymphocyte?
Tk search for infected cells and bind to the cells presenting the complementary antigen
Tk then SECRETE enzymes/hydrogen peroxide into infected cells to kill it and the pathogen
What is the role of T-helper lymphocytes?
T-helper lymphocytes release cytokines (interleukins)
Cytokines are chemical messengers that activate and stimulate B-cells
Step 4: T-lymphocyte
Following the initial immune response some T-killer or T-helper cells remain behind as T memory lymphocytes Tm and provide immunological memory
Why is it important to have some T-cells remain behind as memory T-cells?
At a second encounter with the invader, Tm cells can reproduce to create a FASTER and STRONGER immune response than the first time the immune response responded to the invader.
Step 5: T-lymphocytes
T-regulatory lymphocytes Tr shut down the immune response after the pathogen has been successfully removed
They are sometimes referred to as IMMUNOSUPPRESSIVE and are involved in preventing autoimmunity
What is an autoimmune disease?
An autoimmune disease is a disease that occurs when there is an:
Abnormal immune response against parts/tissues of the body
When does an autoimmune disease occur?
An autoimmune disease occurs when the antibodies start to attack our own antigens.
What are the causes of autoimmune disease?
The causes of autoimmune disease are unknown but seem to include both genetic and environmental factors
Define rheumatoid arthritis?
This is a painful inflammation of a joint
What is the cause of rheumatoid arthritis?
The cause is uncertain
What causes rheumatoid arthritis?
It starts with antibodies attacking the SYNOVIAL membrane around the joint
Define LUPUS?
Lupus can affect any part of the body, causing swelling and pain.
Lupus may be associated with antibodies that attack certain proteins in the nucleus in cells and affected tissues
Symptoms of lupus?
Lupus can cause HAIR LOSS
Lupus can cause RED-RING SHAPED, scaly patches or lesions on the skin at the upper back,neck, face and arms
Lupus can cause abnormally high sensitivity to SUNLIGHT, UV rays or fluorescent
Lupus can cause a butterfly skin rash on face, legs and arms
Lupus can cause MOUTH ULCERS
What type of specific immune response are B-lymphocytes involved in?
B-lymphocytes are involved in the humoral response because they target pathogens in the body fluid (humours) e.g. Blood/tissue fluid/lymph
Step 1 of how B-lymphocytes respond?
Antigen is detected by a particular B- lymphocyte that has an antibody on its surface which is complementary to the antigen
What is the major difference between how a T-lymphocyte and B-lymphocyte are activated?
B-lymphocytes recognise and are activated by pathogens carrying a particular antigen.
They are not activated by antigen-presenting cells
How will most B-lymphocytes spend their lives?
Most B-lymphocytes will spend all their lives without anything happening to them at all, because they never meet their particular antigen
Step 2, B-lymphocytes?
Once a particular antigen is recognised by a B-lymphocyte it becomes selected
This is known as clonal selections
What must take place before clonal expansion takes place?
The selected B-lymphocyte will not begin to divide until it becomes activated to do so.
It is the T-helper cells which release (CYTOKINES) INTERLEUKINS that stimulate B-lymphocytes to divide and differentiate
STEP3 B-lymphocyte?
Once activated the selected cell begins to divide by mitosis
This is known as clonal expansion
Step 4: B lymphocytes?
As the B-lymphocytes divide they also begin to differentiate into different types.
What are the 2 types of B-lymphocytes?
Plasma cells
Memory B-cells
Describe plasma cells?
Plasma cells secrete antibodies which are complementary to the antigen
Describe the role of memory B-cells?
These are long-lived/remain in circulation and provide IMMUNOLOGICAL MEMORY
Provide a secondary response to the pathogen which is FASTER STRONGER than previous immune response to same antigen
What are antibodies also known as?
Immunoglobulins
Define antibodies?
Antibodies are Y-shaped protein molecules produced by B-lymphocytes (PLASMA CELLS) in response to an infection.
Antibodies are capable of IDENTIFYING and NEUTRALISING antigens.
Describe the structure of an antibody:
Y-shaped molecule consisting of 4 polypeptide chains (2 light & 2 heavy chains) Variable region Constant region Disulphide bridges Hinge region
Describe the variable region?
Variable region - this ensures antibody specificity (differs from 1 type of antibody to another)
Has complementary shape to the antigen on the pathogen
Describe the constant region?
- the constant region is the same in all antibodies
- the constant region allows it to bind to phagocytes
Describe a disulphide bridge?
The disulphide bridges help hold the tertiary structure of the molecule
Describe the hinge region?
The hinge region allows flexibility and binding of more than one antigen
How do most antibodies work?
Most antibodies work by attaching to the antigens on a pathogen.
What are the possible effects of antibodies attaching themselves to antigens?
Neutralisation
Agglutination
Describe neutralisation?
The antibodies cover the binding sites on pathogens or bind to toxins
This helps prevent binding/entry to host cell
How do pathogens enter a cell?
In order for a pathogen to enter a cell it must fuse with the plasma membrane
Describe agglutination?
Large antibodies clump/bind together many pathogens
Thus resulting in clumps which become too large to enter host cell and also means there is an increased likelihood of being consumed by a phagocyte
Describe opsonisation?
These are a group of antibodies that bind to the antigens on a pathogen and then act as binding sites for phagocytic cells
OPSONINS therefore increase the likelihood of phagocytosis as phagocytes can bind more easily to the pathogen and destroy it
What are the molecules called that pathogenic cells (bacteria) release which makes people feel ill?
TOXINS
Describe the role of anti-toxins?
Some antibodies bind to the molecules that are released by pathogenic cells.
These molecules may be toxic and the action of anti-toxins makes them harmless
What is meant by the primary response?
When an infected agent is first detected there is delay before the appearance of antibodies in the blood.
This is the primary response
Why is there a delay in antibody production during the primary response?
As it takes time for the following to occur: - antigen presentation - clonal selection - clonal expansion - differentiation - productions of antibodies Also there are no memory cells
Describe what is meant by secondary response?
Upon a second infection by the same pathogen:
Antibody production starts much sooner (more rapid)
Antibody concentration reaches a higher concentration
This is the secondary response
What happens to the number of antibodies in the blood once the pathogen has been dealt with?
Once the pathogen has been dealt with, the number of antibodies in the blood drops rapidly
However MEMORY B CELLS remain in the blood and provide immunological memory
