Biol 1057 - cell recognition and immune system Flashcards
Outline the tyoes if oathogens and immune systems role
➢Pathogens (foreign substances) such as
o Viruses
o Bacteria
o Fungi
o parasites
➢The immune system has a vital role in protecting the body by
o Killing and removing pathogens
o Destroying cancer cells
Explain how the immune system is activated
➢ Antigens (proteins) on the surface of pathogens are
recognised by special receptors on the immune cells.
➢ Triggering a series of processes in the body (Immune
response).
Briefly outline the 3 layers of defence
o Physical and Chemical Barriers
* skin, mucosa, epithelial surfaces
o Innate Immune Response
* Specialised cells
* Phagocytosis
* Inflammation
o Adaptive Immune Response
* Specialised Cells
* Antibodies
Outline physical and chemical barriers
o Skin
* keratin of the skin prevents microbial growth
o Mucous membranes
* lining the respiratory, digestive, reproductive, and urinary tracts
* cilia that line the upper respiratory tract sweep mucus and trapped particles up into the
throat, where they can be coughed, expelled or swallowed.
o Perspiration, saliva, and tears
* contains antibacterial enzymes.
o Urine
* flushes bacteria from the urinary tract.
o Acid pH
* stomach, vagina
o Normal flora
* microbes in the mouth and intestine.
Briefly outline white blood cells
➢Cells of the immune system involved in protecting the body against pathogens.
➢Produced and derived from multipotent cells in the bone marrow known as
haematopoietic stem cells.
➢Found throughout the body, including the blood and lymphatic system
Types of white blood cells are granulocytes (neutrophils, eosinophils, and
basophils), and agranulocytes (monocytes, and lymphocytes [T cells and B cells])
Define stem cells and progenitor cells
Stem cells: Cells with the capacity to divide
and differentiate to a wide range of cell types.
Progenitor cells: Cells with the capacity to divide
and differentiate to a narrow range of cell types
Briefly outline the lymphatic system
Lymphatic vessels and lymphatic organs
➢ The lymphatic vessels drain excess fluid from the tissues
and return it to the blood.
➢ White blood cells also travel in lymphatic vessels as well
as in the blood.
➢ The lymphatic organs produce and maintain white blood
cells.
➢ Responsible for the production, maintenance, and
distribution of lymphocytes.
➢ Helps defend the body against pathogens.
Outline primary and secondary lymphoid organs
➢ Primary lymphoid organs
o Bone marrow: produces all types of blood
cells including stem cells that give rise to all
white blood cells
o Thymus: maturation site for T cells
➢ Secondary lymphoid organs
o Spleen, lymph nodes: sites where white
blood cells are likely to encounter pathogens
Outline where lymphocytes, b-cells and T cells are found
Lymphocytes - bone marrow
b -cells - produced and mature in bone marrow
t-cells - produced in one marrow, mature in thymus
BRriefly outline the innate immune response
➢If the pathogens escape the physical and chemical barriers they then encounter the
specialised cells of the innate immune response.
➢ Which includes the following processes:
o Inflammation
o Phagocytosis - neutrophils, macrophages, dendritic cells, natural killer
cells etc.
o Protective proteins (in blood, Complement System)
o Fever
➢Immediate Response
Outline the inflammatory response
➢ Localised response to injury x
➢ A wound causes tissue injury and presents an entry
point for pathogens.
➢ Injured cells and mast cells release histamine x, which
dilates the blood vessels near the site of injury.
➢ This allows excess blood flow to the site of injury and
allows white blood cells and platelets to enter the
area.
➢ Platelets release clotting factors to repair the wound. x
➢ The first white blood cells to arrive are
neutrophils. x
➢ They phagocytose (engulf) debris, dead cells
and bacteria.
➢ If neutrophils are overwhelmed, they secrete
chemical mediators (cytokines) to attract
monocytes.
➢ Monocytes differentiate into macrophages
which are more powerful and longer-lived
phagocytes than neutrophils.
➢ Nearby cells secrete chemical factors
(growth factors) to repair the damaged area
Outline phagocytosis
- Phagocyte moves towards pathogen via chemotaxis and surrounds pathogen as recognises foreign antigen
- Phagocyte cytoplasm engulfs the pathogen into vacuole to form a phagosome
- Phagosome and Lysosome fuse and release digestive enzymes lysozymes
- Which hydrolyse/digest the pathogen/bacteria
- Antigens displayed on the cell membrane
Outline protective proteins
- Bind to mast cells and trigger histamine release in inflammatory response
- They can attract phagocytes.
- Bind to the surface of pathogens and tag them for
phagocytosis. - They can form a membrane attack complex that produces
holes in the surface of bacteria, allowing fluid to enter
the bacteria, causing them to burst
Outline the types of protective proteins
➢ Cytokines
o messenger proteins that bind to immune cells and cause them to
divide.
o Attract immune cells to the area or alter their activity e.g. in the inflammatory
response.
o Attract monocytes to the site of injury.
➢ Interferons
o produced by virus-infected cells to alert nearby cells to the infection.
➢ Interleukins
o Largest group of cytokines.
o They facilitate communication between white blood cells.
o Can amplify or dampen immune responses
Outline fever
➢ Common reaction to infection causing rise in body temperature.
➢ Can be triggered by cytokines.
➢ Increased body temperature can help fight infection by:
o Directly inhibiting some bacteria and viruses
o Slowing bacterial growth
o Increasing the phagocytic ability of white blood cells
Outline the adaptive immune response
➢ When innate (non-specific) defences have failed to prevent an infection,
adaptive defences come into play.
➢ Act specifically against individual targets
➢ Involve lymphocytes (B cells and T cells)
o have the capacity to recognise and kill the pathogens
➢ The immune response turns off once the threat is gone
➢ The immune system “remembers” the pathogen and if it encounters the same
pathogen again it can mount a faster immune response.
Briefly define antigens
- Cell surface molecule which stimulates an immune response
- Each lymphocyte can only recognise one specific antigen.
Briefly describe the structure of antibodies
(2 heavy chains)
(2 light chains held by disulfide bridges to connect polypeptide chains)
- Binding sites on the variable region have specific tertiary structure complementary to an antigen
- Rest of the molecule known as the constant region
- 5 classes of antibodies (IgG, IgM, IgA, IgD, IgE).
How do antibodies lead to the destruction of a pathogen?
- Antigen-antibody complex is formed
- Which leads to the destruction of pathogens through agglutination
- Which enhances phagocytosis
Briefly outline T-cells
T cells have receptors that
recognise specific antigens.
➢ T cells can only recognise antigens presented to them by other cells.
o Antigen-presenting cells (APC).
➢ There are two main types of T-cells:
o Cytotoxic T cells: destroy pathogens.
o Helper T cells: secrete cytokines that
control the immune response
Outline which cells are APC
➢ Phagocytes
➢ Cells infected by a virus
➢ Transplanted cells
➢ Cancer cells
Outline cell mediated immunity
- Once the pathogen is destroyed, antigens presented on its cell membrane(APC)
- Complementary acticated T-lymphocyte binds to foreign antigen on APC
- Activating T-lymphocyte, therefore, produces clones of complementary T helper cell by mitosis(clonal expansion)
- Cloned complementary T-helper secrete cytokines cells then stimulate:
=cytotoxic T- cells to kill abnormal body cells
=B-cells (humoral response)
=Phagocytes for phagocytosis
OR become memory cells to respond to another encounter of same pathogen
Outline the role of cytotoxic t cells
➢ Bind to virus-infected or cancer cells (target
cells).
➢ Release perforin molecules that punch holes
in the plasma membrane of the target cell
and form a pore.
➢ Deliver granzymes into the pore that cause
the target cell to undergo apoptosis (cell
death).
➢ Cytotoxic T cells then moves on to the next
target cell.
Outline B- cells
➢ They have surface receptors (B cell receptor, BCR)
that recognise specific antigens.
➢ They can differentiate into plasma cells that secrete
antibodies identical to the B cell receptor.
➢ B cells are responsible for humoral immunity,
Outline humoral immunity
- Antigen binds to the complementary antibody on membrane of the B-cell to form antigen-antibody complex
- Antigen enters the B-cell by endocytosis so B-cell becomes an APC
- Activated complementary T-cell binds to the B-cell causing B-cell to undergo clonal expansion
- B-cells reproduce by mitosis & differentiate into plasma cells OR MEMORY cells(LONG LIVED)
- Plasma cells(SHORT LIVED) secrete antibodies with the complementary variable region to antigen
Outline innate and adaptive immune response
Outline primary and secondary immune response
➢ Primary Response
o First exposure to the antigen.
➢ Secondary Response
o Second exposure to the antigen
o Facilitated by plasma cells
o More rapid
o More antibodies are produced
Outline how antibodies are used for therapeutic and diagnostic purposes
Plasma cells secrete monocolonal antibodies
which can be used to:
o Bind to receptors on cancer cells and block their growth
* Herceptin for breast cancer
o Target cytotoxic drugs to specific cells reducing their side-effects.
o Diagnose disease
* hepatitis, chlamydia, prostate cancer
o Pregnancy testing
Outline the production of monocolonal antibodies
- An antigen is injected into a mouse.
- The mouse naturally produces
lymphocytes, that in turn produce
antibodies specific to the antigen that
was injected. - Cells producing the lymphocytes, are
removed from the mouse. - They are then fused with human cancerous cells called myeloma (tumour) cells to form hybridoma
cells which divide indefinitely. - And produce millions of monoclonal antibodies specific to the original antigen.
- These antibody producing cells are grown and collected in a laboratory.
Outline passive immunity
o Passive immunity
* can be produced by the administration of antibodies
* is short-lived
* does not require direct contact with the pathogen
* anti-venom for snake bites
* immunity acquired by the foetus from maternal antibodies crossing the placenta
Outline active immunity
o Active immunity
* requires direct contact with the pathogen
* stimulates the individual’s immune system to produce its own antibodies
* is long-lasting
* depends on the presence of memory B cells and memory T cells
* includes the immunity acquired naturally with infection (natural active immunity)
* can be produced by vaccination (artificial active immunity)
Outline vaccination
➢ Vaccination results in the production of memory cells that are
quick to respond to a subsequent infection.
➢ For some vaccines, a second administration (booster) is needed to
produce and maintain high levels of immunity.
➢ Herd immunity: when a sufficiently large proportion of the
population is vaccinated, making it difficult for the pathogen to
spread
