Chapter 11 Flashcards
Animal physiology
How does the immune system recognise that a cell is ‘self?
‘Self’ = cell belongs to our own body and shouldn’t be attacked
- surface of our cells contain large carbs, glycoproteins and other polypeptides that can be recognised by our immune system as self
- bacteria, viruses, parasites, cancer cells and other pathogens have an array of molecules on their surfaces
- immune system can recognise these antigens as ‘non-self’- will trigger an immune response against them
NB/ every organism has unique molecules on the surface of its cells
- helps immune system to recognise cells as self
Antigen
any molecule that can trigger an immune response leading to the generation of antibodies
ABO blood group system
- presence of cell surface antigens is the basis for this system
- there’s also the Rhesus factor
Rh+ = found on surface of RBC in people who are rhesus positive
Rh- = when you don’t have the Rhesus factor on surface of RBC
NB/ all RBC have a standard complex carbohydrate, antigen H, on their surface
Blood group A
a molecule of N-acetylgalactosamine is added to antigen H
- has anti-B antibodies
Blood group B
a molecule of galactose is added to antigen H
- has anti-A antibodies
Agglutination
when antigens on the surface of RBC stimulate antibody production in a person w/ a different blood group
Blood group AB
- has both A and B antigens on RBC surface
- hence, body doesn’t have antibodies to A or B
- universal recipient because they can receive blood from any blood type
Blood group O
- has no A or B antigens
- but it has anti A + B antibodies (don’t affect transfusion)
- universal donor because it contains neither A or B antigens on RBC surface
Haemolysis
breakage of RBC membrane
- leads to release of haemoglobin and other internal components into the surrounding fluid
- agglutination will lead to haemolysis and may result in the death of the patient
Cellular immune response
- Antigen is ingested, via phagocytosis, by macrophages and B cells
- Both process and present antigen on their surface
- only B cells w/ antibodies that can bind the antigen will take in antigen for processing
- only B cells that can produce specific antibodies against antigen are selected for cloning later - Macrophage interacts w/ a helper T cell, activating it
- Activated helper T cell interacts w/ B cell that has antigen on its surface, and activates it
- Activated B cell rapidly divides by mitosis to form clones of plasma cells and memory cells
- Memory B cells stay in body for years after both plasma cells and antibodies have disappeared
- if an infection w/ same antigen recurs, memory B cells quickly divide to form plasma cells and new set of memory cells
- secretes specific antibodies against this specific infection
- memory cells provide long-term immunity to disease
Plasma cells
- produce antibodies of one specific type against the antigen
- have lots of rER and a well-developed Golgi apparatus
Antibodies
Antibodies: proteins that bind to foreign substances
- produced one immune system has reacted to invasion of an antigen
- help to destroy the antigen
- has a constant and variable region
Variable region: part of antibody which is highly specific to a particular antigen- long and short chains are held together by disulphide bonds
Immunity
To be immune against a certain infectious pathogen:
- body needs antibodies that are already in your blood
- or has memory cells that produce a specific antibody against this type of infective agent
Opsonisation
coating of a pathogen w/ antibodies to promote and enhance phagocytosis
Complement proteins
- group of more than 20 proteins that are present in blood and tissue fluid
- normally inactive
- some become activated when they are presented w/ antigens, this is fulfilled by antibodies
Process of opsonisation
- an antigen bound to an antibody is presented to a complement protein
- complement protein is cleaved, to produce activated protein- binds to membrane proteins of pathogens
- this creates pores in the membrane of the pathogenic cell, leading to its lysis or increases its chance of being engulfed by a phagocytic cell
- activated complement proteins may trigger release of histamines from basophils
- can also attract phagocytes to infection sites to enhance elimination of pathogens
Antigens vs. antibodies
Antigens: any entities that trigger an immune response
- eg. virus, bacterium, parasites, fungus or large glycoprotein
Antibodies: proteins produced by plasms cells ( a B cell originally) in response to an antigenic reaction
Primary immune response
Immune response triggered on the first encounter of the body w/ an antigen
What happens after primary immune response?
Following primary response, memory cells produced ensure that, if another infection w/ same pathogen occurs, body responds quickly
Secondary immune response
immune response stimulated on the second exposure to the same antigen
Describe the primary and secondary immune response
- initial conc. of antibodies to antigen A drops quickly
- memory cells produced during first infectious period ensure that when immune system is challenged a second time w/ same antigen A, reaction is faster
- when immune system is challenged a second time, memory cells (formed during primary response) divide by mitosis to form clones of plasma cells and memory cells
- plasma cells produce antibodies to give a fast response to invading pathogen
- the memory cells stay in the body to defend against any future attack
Why is the secondary immune response faster than the primary one?
The fact that memory cells can directly give rise to plasma cells without the need for antigen presentation or activation of helper T cells and B cells, allows secondary response to be much faster than the primary response
Vaccinations
- inject an attenuated form of pathogen or a toxin that is produced by the pathogen into the body
- vaccines contain antigens that trigger immunity but don’t cause disease
- inactivated toxin triggers a primary immune response resulting in production of antibodies and memory cells
- when actually infected by the toxin, memory cells can produce massive amounts of antibody
- ensures that macrophages and other killer cells can dispose of the infection
Zoonosis
transmission of a disease from animals to humans