Immune System Flashcards
what forms the immune system?
white blood cells
What pathogens can the immune system fight?
Viruses
- Bacteria
- Fungi
- Worms
- Protozoans
Role of the immune system
Detect non-self (pathogens) + respond by removing non-self invaders
A pathogen?
Agent that causes disease, can be cellular or non-cellular
What can white blood cells have?
- non-specific generalized response
- specific targeted response
What does the lymphatic system contain?
Spleen
- Thymus
- Lymph nodes
- Bone marrow
- An open network of lymphatic vessels
what happens when it is a open Lymphatic System?
the vessels have an open ending and can collect excess fluid including pathogens
what happens when it is a closed Lymphatic System?
such as in the circulatory system it means arteries, capillaries and veins all join, and blood flows continuously through them in the circuit.
what is Lymph?
Tissue fluid and white blood cells (leukocytes)
Role of the lymphatic system?
- Return excess tissue fluid back to the circulatory system
2. Transport antigen presenting cells (type of WBC) to lymph nodes where specific immune response is triggered
What are lymph nodes?
Part of the lymphatic system where specific immune response takes place
Role of Lymph nodes?
- Contain lymphocytes (T+B Cells)
- Filter and trap pathogens and cancer cells
- A specific immune response can be triggered here
Which WBC have a non-specific immune response?
Natural Killer Cells
Basophils
Natural Killer Cells?
- Kills virus infected and tumour cells
Basophil (inflammation)
secretes histamines
Which WBC are phagocytes?
Neutrophil
Macrophage
Neutrophil?
- Engulfs foreign particles and microorganisms
Macrophage?
- Engulfs foreign particles and microorganisms and secretes component proteins
Which WBC are Involved in specific immune responses?
Eosinophils B cell T helper Cells Cytotoxic T cell Platelets (blood clotting)
Eosinophils
- Secretes enzymes that break down cell walls in pathogens
B cell
- Activated plasma cells produce antibodies
- Memory B cells provide immunity
T Helper Cells
- Secretes interleukin to stimulate
o B and T cells, to divide
o Action of macrophages and neutrophils
Cytotoxic T cell
- Produce chemical that cause death in foreign, infected and altered cells
- Memory TC cells provide immunity
Platelets
- Cellular fragments without a nucleus they assist blood clotting and wound repair to prevent entry of pathogen
why is essential to distinguish self from non self?
is vital for specific and non-specific immune responses in order to detect and respond to foreign material
What do foreign material have that recognize foreign immune cekks
their own self markers (antigens)
Does the response alter in 1st and second?
does not alter, even if the same pathogen is encountered ( no memory of previous pathogens)
4 ways of preventing entry of foreign material in first line defence
- Intact skin
o A physical barrier - Mucus and cilia
o Trap pathogen and also acts as a protective barrier - Natural secretions
o Contain bactericidal agents such as enzymes (in tears, saliva) or stomach acid - Commensal Organism
o Inhibits growth of pathogenic bacteria as they take up space and nutrients inhibiting the growth of potential pathogens
Why are open wounds dangerous?
provide entry for pathogen, there fore important to have blood clotting
blood clot structure?
Wound arteries constrict platelets clump fibrinogen fibrin factor 8 (forms) blood clot!
How does the second line of defense occur?
initiated after the foreign material has entered
- Inflammation
Non-specific, same level of response, even if pathogen encountered
- Phagocytosis
= recognise, engulf and destroy microorganisms and debris, using digestive enzymes
What phagocytes can be used in phogocytosis?
- Neutrophils and monocytes
o In blood - Macrophages and dendritic cells
o In tissues
- Complement
- The biochemical cascade of more than 20 blood proteins
Complement is activated by presence of antigen/antibody complexes formed as a result of the specific immune response and by the pathogen it self
Functions of complement
- Cell membrane is ruptured (not cell walls)
- Attract phagocytes (chemotaxis)
The phagocytes help to remove ab/ag complexes - Coat bacteria (= opsonisation) which enhances phagocytosis (to engulf the bacteria)
- Cytokines
Signalling molecules (messengers) of the immune system
- Their effect is dependent on cells having appropriate receptors for the cytokines
- They’re released by cells (often th, any wbc) after tissue injury or infection
What do cytokines trigger?
- non-specific immune responses such as activation of macrophages, inflammation and blood clotting
- Specific immune responses such as increasing the antibody response
How are cytokines similar to hormones?
as they are found circulating in blood must bind to specific receptor to cause a cellular response
How are cytokines different to hormones?
- Many different cells can produce cytokines and can act on wide variety
- Less cytokines than hormones
- Interferon
Particular type of cytokine produced by wbc and by virally infected cells
- Makes cells more resistant to infection by stimulating the production of antiviral proteins
o Activates NK cells and macrophages to help remove the viral infection
- Natural Killer cells
Major role in the rejection of tumours and cells infected by virus
- Can be activated by cytokines
- They kill by expressing a death signal or releasing chemicals such as perforin, triggering apoptosis of the infected cell so the virus cannot be spread
- Fever
Develops in response to
- Cytokines from macrophages
- Pyrogens (toxins released) from bacteria
High temps can inhibit bacterial growth but increase human enzyme activity and production of immune cells.
Third line of defence is…
- Slower than non-specific
- Provides long lasting immunity due to memory cells
- On repeat infection by same organism, response is greater and quicker
Antigen
- Part of the foreign material that is recognised as foreign and initiates an immune response
Antibody
Protein produced by specific plasma cells, their purpose is to bind antigens and inactivate them, are part of humeral immunity
Are antibodies specific?
- Specific and made in response to antigens. ( Epitopes must fit the antigen bonding site of the antibody)
Where are antibodies found and what are they involved in?>
- Involved in humoral immunity
- Found free within blood and surface of B lymphocytes
What are antigen presenting cells?
- Include macrophages, dendritic cells and B cells
- Macrophages and dendritic cells engulf (via phagocytosis), and display the fragments of the foreign material on their MHC Class II markers
- Binding antigens makes them activated and they migrate to local lymph nodes to activate T cells, therefore stimulating cell immunity
What cells are involved in Cell Mediated Specific Immune Response?
- T cells involved
o Produced in bone marrow, mature in thymus
o They migrate to the lymph nodes - Two main types
o T helper
o T cytotoxic - Most effective in removing virus infected cells
o Also participate in defending against fungi, protozoans, cancers and intracellular bacteria.
o Major role in transport rejection
What are T helper lymphocytes
- Require the antigen to be presented to them on a Antigen presenting cell = macrophage or dendritic cell
- T cells have T cell receptors on their surface that recognise foreign antigen on the APC
- When specific T cell is stimulated, clonal expansion follows so there are many T helper cells specific for that antigen,
Memory T cells are also produced
what happens when T helper cells are activated?
they release cytokines that
o Allow B cells to differentiate into antibody producing plasma cells and memory cells (part of the specific immune response)
Can activate Tc
Increase NK cell activity and phagocytosis (parts of the non-specific immune responses)
What are t cytotoxic cells used for?
killing any host cells that have been infected by viruses
o Display fragments of the antigen on their surface which can be recognised by the T cytotoxic cells as foreign
o Can kill cells often before the virus can release a fresh crop of viruses
- Useful in fighting cancerous cells, which have new and foreign antigens on their surface
- Involved in transplant rejection if the donated tissue is not well matched for the MHC markers, so the donated tissue is recognised as foreign and destroyed by the patient
What are T cytotoxic cells stimulated by?
APC or by Th cells or by recognition of foreign fragments of the antigen on the surface of any infected cells
What is the humoral response?
- Refers to the immune response mediated by antibodies (released from plasma cells). T helper cells essential to complete the response
- Specific antibodies bind to the antigens (of bacteria), antigen/antibody complex and they cross link. This is called Aggulination
what is agglutination?
– activates complement and phagocytosis
B cells?
o Produced in the bone marrow, migrate to the lymph noes
o Have antibodies on their cell membrane and these act as the receptors for the antigens
o B cells are specific (like T cells), can only bind with one type of antigen
o Only a few B cells are made with any one surface
Memory cells?
o After an infection has been removed, most pf the memory cells are no longer required and they are killed by apoptosis (organised cell death, where organelles can be recycled)
o SAVES SPACE WOOHOO
What is the clonal selection theory?
During Embryonic development millions or randomly generated B cells are formed
These are able to recognize many different antigens including those that have never ever been encountered
The variety of B cells is possible to the structure of antibodies
Advantage of active immunity?
- Long term immunity due to the production of memory cells
On a second injection get a quicker, larger and longer lasting secondary response - Due to pre-existing memory cells specific to the pathogen
Herd Immunity
- Where the majority of the population is immune to a particular disease, usually by vaccination. This prevents the spread of diseases to more vulnerable of the community.
Advantage and Disadvantage of herd immunity?
ad - Does provide short term immunity to pathogens by the Ab’s binding to the foreign antigens + agglutinate them
dis- - Only short term immunity and does not produce memory cells for long term immunity
Where do Antibodies from passive immunity come from?
- Specific antibodies can come from horses or rabbits that have not been exposed to the antigen
o Initially the does of toxin is very small, to not kill the animal but enough to stimulate antibody production and memory cells - B cells can be cultured in a laboratory and the antibodies is collected
- Fusing mouse B cells with tumour cells.
o Each hybrid cell produces clones of itself and each clone produces the same antibody = monoclonal antibodies
- Hypersensitivity
Sometimes the immune system reacts to antigen that cause no real threat to body, but the subsequent immune response can cause moderate to serious tissue damage and even death
1a. Allergies
A rapid and vigorous overreaction of our immune system to a previously encountered antigen – which is called an allergen as it produces an allergic reaction
Treatment of allergic reactions
- To administer anti-histamine to suppress some allergic reactions
Cortisone can be used as it reduces the immune system in general - To desensitise people by the repeated administration of tiny amount of allergen extracts under the skin. Specific IgA antibodies are made against the allergen.
