11.1 THE IMMUNE SYSTEM
- Created by: lineventer
- Created on: 07-01-21 14:51
Identifying Pathogens Revision
Every body cell has a common set of plasma membrane proteins. White Blood Cells recognize the set of proteins that are "self". Pathogens has different proteins (Antigens) that are "not self" and this causes the production of Antibodies
Antigens: Any molecule that can trigger an immune response leading to generation of antibodies
Antibodies are specific to antigens therefore foreign antigens are recognized and antibodies are then produced
ABO blood type classification uses the presence/absence of a certain antigen on red blood cells
Specific Immune Response
- Pathogens ingested by Macrophages
- Antigens from the pathogen are now displayed in the plasma membrane of Macrophage
- Helper T cells bind to the antigens displayed by the Macrophages
- When Helper T cells bind to the antiges Helper T cells are activated by the Macrophage
- The activated T cells then bind to Lympocytes called B cells
- The Helper T cell activates the selected B cell through binding and also releasing a signalling protein
Specific Immune Response
- Macrophages ingest pathogens via phagocytosis and present the antigen on their surface
- Helper T cells bind to the antigens displayed on the Macrophages and become activated
- Activated T cells bind with B cells while causing the B cells to activate through binding and release of a signalling protein
- Activated B cells rapidly divide by mitosis to form plasma cells that produce a large number of specific antibodies
- Antibodies destroy the pathogen
- Antibodies and plasma cells persist temporarily
Small number of plasma cells remain long after infection and become memory cells
Memory cells are then inactive till the body faces the same pathogen then allowing the memory cells to become activated leading to a faster response
- Macrophage presents antigen
- Helper T lymphocyte becomes activated
- B lympocyte becomes activated
- Plasma - secrete antibodies
- Memory - long lived in bloodstream
Antibodies
Antibodies: (Immunoglobins) Y shaped protein produced mainly by plasma cells
Antibodies aid in the destruction of pathogens:
- Opsonization: Make pathogen more recognizable to phagocytes so pathogen is more readily engulfed. Once bound they link the pathogen to the phagocyte
- Neurtalization of viruses and bacteria: Prevent viruses from docking to host cells
- Neutralization of toxins: Bind to toxins produced by antibodies
- Activation of complement: A collection of proteins which ultimetly lead to the perforation of pathogen membranes by forming a pore in the membrane allowing water and ions to enter the cell causing the cell to lyse
- Agglutination: Cause pathogens to stick together so they are prevented from entering cells and easier for phagoctyes to ingest
Immunity
Immunity is due to:
- Presence of antibodies that recognize antibodies
- Memory cells that allow for the production of antibodies
Primary Immune Response: Launched the first time pathogen infects the body
Secondary Immune Response: Launched second time pathogen infects the body
Memory cells ensure the second time an antigen is encountered the body is ready to respond rapidly by producing antibodies at a faster rate
Vaccine
Vaccine: Live attenuated (weakened) version of the pathogen
- A vaccine is introduced (usually through injection) into the body
- Stimulates a primary immune response
- If the pathogen enters the body it is destroyed by antibodies during a secondary immune response which is much faster and stronger so little to no symptoms are experienced
Smallpox
Smallpox was the first infectious disease to have been eradicated by vaccination
Cowpox is a mild viral infection of cows very similar to Smallpox
Edward Jenner's procedure:
- 1796 delibrately infected an 8 year old boy with Cowpox using the blisters of a milkmaid who had this disease
- Attempted to infect the boy with Smallpox but found that he was immune
- This testing was repreated on a small group of people and Jenner himself
Jenner's testing procedure is considered unethical:
- No prior research had been done before human testing to determine the effectiveness and possible side - effects
- Informed consent was not given
- Initial testing was done on a child which would not be approved
Epidemiology
EpIdemiology: The study of the distruction patterns and causes of a diseases in a population
By studying the spread, patterns and causes of diseases predictions can be made and preventative measures taken. Results from epidermological studies can help predict where outbreaks may occur and how to contain them.
Histamines
Histamine: Small organic molecules produced by two types of leukocyte - basophils and mast cells
Key effect in the immune response: Increases permeability of capiliaries to white blood cells and other proteins such as antibodies
Function of Histomine:
- Dialation of small blood vessels in the infected area causing the vessels to become leaky
- Increases the flow of the fluid containing immune components to the infected area
- Allows some of the immune components to leave the blood vessels resulting in both specific and non-specific responses
This allows the components of the immune system to engage the pathogen early at the site of infection
Histamines and Allergies
Cells have histamine receptors
Histamine trigger symptoms of allergy:
- Nose itching, fluid build up, sneezing, inflammation
- Allergic rashes
- Anaphylaxis (dangerous swelling)
To lessen effets of allergic responses - Anti-Histamines can be taken
Zoonotic Pathogens
Zoonosis: Pathogen which can cross a species barrier
A major contributing factor to this is the growth of contact between animals and humans such as living in close contact with livestock or the disruption of habitats.
Measels, Polio and Syphillis pathogens are species-specific and only affect humans
Flu, Ebola and Salmonella can be transmitted between humans and other animals
Monoclonal Antibodies
Monoclonal Antibodies are used for the treatment and diagnosis of diseases
Examples are:
- Test for malaria to identify whether either humans or mosquitoes are infected with the malaria parasite
- Test for the HIV pathogen
B cells are fused with Myeloma which produced many different hybridoma cells
Each Hybridoma cell is tested to find the cells that produces the required antibody
The desired Hybridoma cells is then allowed to divide and form a clone
The clones secrete the orginal antibody produced by the original Lymophocyte
- An animal is injected with an antigen and in response produces specific plasma cells
- The plasma cells are harvested from the spleen of the animal
- Harvested plasma cells are fused with tumor cells forming hybridoma cells
- Hybridoma cells are screed to see which ones are producing useful antibodies
- The selected hybridoma are allowed to divide and produce clones
Monoclonal Antibodies in Pregnancy
Monoclonal Antibodies are used in pregnancy test kits
The urine of pregnant women contain hCG: protein secreted by the developing embryo and later by the placenta
Pregnancy test kits contain monoclonal antibodies to which hCG binds. This causes a coloured band to appear indicating that hCG is present in the urine sample and that the woman is pregnant
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