Immune defences Flashcards
(43 cards)
What are the three defence mechanisms of the body that are used to protect itself from pathogens and foreign matter?
- Natural barriers
- innate immune response
- adaptive immune responses
What are the three types of natural barriers?
Provide examples.
- chemical: acids, enzymes (in saliva or tears), mucus, sebum, swear,
- mechanical: intact skin, mucous membranes, cilia, nasal hairs
- microbiological: gut flora
How can the body distinguish from self and non-self cells?
Self-cells contain molecules present on the surface of their cell membranes that identify themselves as belonging to the body while non-self cells contain surface molecules (antigens) that the body recognises as not belonging to the body.
Why does the body need to distinguish between self and non-self cells?
White blood cells play a vital role in the non-specific and specific defence. It is important that when defending the body against pathogens white blood cells are able to distinguish foreign cells from those of our own body.
This….
What is the difference between class 1 MHC markers and class 2 MHC markers?
MHC 1 markers are located on the surface of all human cells with a nucleus whereas MHC 2 markers are only located on antigen presenting cells.
These markers are treated in a different manner by white blood cells.
Where are blood cells produced?
Produced in the bone marrow of long bones.
Which type of blood cell leaves the bone marrow in an immature state?
T cells (T lymphocytes). The migrate to the thymus gland which is their site of maturation.
Do all blood cells look the same?
No, all blood cells take on different looks as they have different roles.
What is the first line of defence?
The body’s natural barriers.
- part of the defence against pathogens provided by the mechanical, chemical and microbiological barriers of the innate immune system that prevent entry of pathogens into the body.
What is the second line of defence?
Involves innate responses to the presence of foreign particles.
- consists of the actions of immune cells and soluble proteins mounting a rapid but non-specific attack against pathogens that gain entry to the body.
- cannot distinguish one type of microorganism from another
What is a phagocyte? (4)
- a white blood cell which engulfs pathogen via phagocytosis
- formed in bone marrow and flow through lymphatic and circulatory system
- the lysosomes present in the phagocyte destroys the pathogen with enzymes
- includes macrophages, dendritic cells and neutrophils
What are the cells of the second line of defence?
Use the acronym!
Please bring home no more pathogens.
- Phagocyte
- Basophil
- Histomine
- Neutophil
- Macrophage
- platelets
What are complement proteins?
Provide 2 examples.
A group of proteins that assist phagocytes in recognising the presence of pathogens
eg antibodies, interferons
What is an interferon?
State the cause and effect.
- A chemical (cytokine) that is secreted by viral infected cells.
- The release of interferon makes adjacent uninfected cells more resistant to the virus (reducing chance of infection).
- It triggers cells to make enzymes which prevent the virus from making more copies of itself.
- successful against viruses that do not travel far.
What is inflammation?
What is released?
A reaction to infection whereby histamines (from mast cell) causes local arterioles to expand, drawing more blood into the area.
Histamine causes capillaries to become highly permeable allowing macrophages and neutrophils to pass out of the bloodstream to the infected area.
What is the temperature response?
When macrophages recognise a foreign cell they release the cytokine; interleukin 1.
This causes the hypothalamus to reset, resulting in a fever.
The high body temp is an unfavourable condition for the pathogen (limits reproduction) hence providing WBC a better chance to defend.
What is the lymphatic system?
A system of vessels and lymph nodes which plays a vital role in defending the body against the myriad of pathogens.
Is the lymphatic system a one-way system?
No, the system contains valves which prevent the backflow of fluid. The system relies on muscle contranctions to circulate the lymoh fuid around the body.
What are lymph nodes?
Sections filled with WBC which filter lymph passing through the body. Antigens will pass though here and meet lymohcytes.
They swell during infection as lymphocytes are multiplying rapidly in order to overcome invader.
What are the primary lymphoid organs?
Generate lymphocytes from immature progenitor cells.
- bone marrow
- thymus
What are the secondary lymphoid organs?
Sites where mature B and T cells are activated by meeting complementary antigens, developing into effector cells.
- lymph nodes
- the spleen
What is the third line of defence?
A form of specific immunity in which people produce their own antibodies to a particular antigen.
Involves action of b cells and t cells.
What is the primary response of the adpative immune system?
Occurs after first contact with pathogen
- Mactrophage captures pathogen and displays fragmnets of its antigen on an MCH2 marker.
- Macrophage binds with a t-helper cell and M releases interleukin one which activate T helper cell
- T helper cell releases interleukin 2, activating other lymphocytes
What is the cell-mediated response?
Involves action of T cells on intracellular pathogens
- the T helper cell directly binds to the MCH 2 marker on M and becomes activated when M releases interleukin 1
- the activated T cell releases interleukin 2, stimulating other helper T cells, cytotoxic t cells and b cells that are specific to that disease to become activated. Clonal selection
- Helper t cells will differentiate into t memory cells which remain in the lymph nodes
- the cytotoxic t cells will attack infected cells. they use their t cell receptors to recognise MCH1 markers on cells, they bind to marker and secrete perforin proteins.
- these proteins punch holes in the membrane of infected cells and stimulate cell to undergo apoptosis
- suppressor t cells then turn off immune response once infection has been eradicated
