11.1 Antibody Production Flashcards
What does it mean if the immune system can differentiate between self and non-self?
The immune system has the capacity to distinguish between body cells (‘self’) and foreign materials (‘non-self’)
What does the immune system attack? self or non-self?
non-self
It will react to the presence of foreign materials with an immune response that eliminates the intruding material from the body
What identifies cells as “self”?
All nucleated cells of the body possess unique and distinctive surface molecules that identify it as self
What are self markers called?
These self markers are called major histocompatibility complex molecules (MHC class I) and function as identification tags
WIll the immune system react to self markers?
no
The immune system will not normally react to cells bearing these genetically determined markers (self-tolerance)
What can be categorised, as non-self?
Any substance that is recognised as foreign and is capable of triggering an immune response is called an antigen (non self)
What recognises antigens and what do they do?
Antigens are recognised by lymphocytes which bind to and detect the characteristic shape of an exposed portion (epitope)
What do lymphocytes trigger?
Lymphocytes trigger antibody production (adaptive immunity) which specifically bind to epitopes via complementary paratopes
What are 3 antigenic determinants?
Surface markers present on foreign bodies in the blood and tissue – inluding bacterial, fungal, viral and parasitic markers
The self markers of cells from a different organism (this is why transplantation often results in graft rejection)
Even proteins from food may be rejected unless they are first broken down into component parts by the digestive system
Where are self-markers present?
Self markers (MHC class I) are present on the surface of all nucleated body cells and identify the cell as part of the organism
Do all organisms have the same self markers?
no
Different organisms have distinct self markers which prevent transplantation of tissues (unless a very close genetic match)
Do RBC have self markers, why?
they do not - Red blood cells are not nucleated and hence do not possess the same distinctive and unique self markers as all other body cells
Due to RBC not being nucleated, what can be done to blood cells?
This means that red blood cells can be transferred between individuals without automatically causing immune rejection
Despite not having self markers, what may they contain?
However, red blood cells do possess basic antigenic markers which limit the capacity for transfusion (the ABO blood system)
What type of antigenic markers may red blood cells possess?
Red blood cells may possess surface glycoproteins (A and B antigens) either independently (A or B) or in combination (AB)
Can red blood cells have no surface glycoproteins?
yes
Alternatively, red blood cells may possess neither surface glycoprotein (denoted as O)
Why are blood transfusions not compatible between blood groups?
As humans produce antibodies against foreign antigens, blood transfusions are not compatible between certain blood groups
What blood groups can AB blood RECEIVE transfusions from?
AB blood groups can receive blood from any other type (as they already possess both antigenic variants on their cells)
What blood groups can A blood NOT RECEIVE transfusions from?
A blood groups cannot receive B blood or AB blood (as the B isoantigen is foreign and will stimulate antibody production)
What blood groups can B blood NOT RECEIVE transfusions from?
B blood groups cannot receive A blood or AB blood (as the A isoantigen is foreign and will stimulate antibody production)
What blood groups can O blood RECEIVE transfusions from?
O blood groups can only receive transfusions from other O blood donor (both antigenic variants are foreign)
What results in positive or negative blood groups?
An additional glycoprotein (Rhesus factor) is either present or absent, resulting in positive and negative blood groups
What is a pathogen?
A pathogen is an agent that causes disease – either a microorganism (bacteria, protist, fungi or parasite), virus or prion
What is a disease?
A disease is any condition that disturbs the normal functioning of the body (i.e. the body can no longer maintain homeostasis)
What is an illness?
An illness is a deterioration in the normal state of health of an organism (a disease may cause an illness)
Are pathogens species-specific?
YES
Pathogens are generally species-specific in that their capacity to cause disease (pathogenesis) is limited to a particular species
What are examples of diseases that affect human hosts?
Polio, syphilis, measles and gonorrhoea are examples of diseases caused by pathogens that specifically affect human hosts
Can certain pathogens cross the species barrier?
YES
Certain pathogens may cross the species barrier and be able to infect and cause disease in a range of hosts
What are zoonotic diseases?
Diseases from animals that can be transmitted to humans are called zoonotic diseases (or zoonoses)
What are examples of zoonotic diseases?
Examples of zoonotic diseases include rabies (dogs), certain strains of influenza (e.g. bird flu) and the bubonic plague (rats)
In what 4 methods can disease transmission occur?
direct contact
contamination
airborne
vectors
How can diseases spread via direct contact?
the transfer of pathogens via physical association or the exchange of body fluids
How can diseases spread via contamination?
ingestion of pathogens growing on, or in, edible food sources
How can diseases spread via airborne?
certain pathogens can be transferred in the air via coughing and sneezing
How can diseases spread via vectors?
intermediary organisms that transfer pathogens without developing disease symptoms themselves
In what two ways will the body respond to foreign pathogens?
When the body is challenged by a foreign pathogen it will respond with both a non-specific and a specific immune reaction
How does the non-specific response work?
Non-specific immune cells called macrophages will engulf pathogens non-selectively and break them down internally
What do a proportion of macrophages display?
A proportion of macrophages (dendritic cells) will present the antigenic fragments of the pathogen to specific lymphocytes
What can T and B lymphocytes be labelled as?
specific
The body contains millions of different T lymphocytes and B lymphocytes that each recognise a single, specific antigen
- why do macrophages present antigenic fragments?
Antigenic fragments are presented to specific helper T lymphocytes (TH cells) that, when activated, releases cytokines
- what do cytokines stimulate?
The cytokines stimulate a specific B cell that produces antibodies to the antigen to divide and form clones (clonal selection)
- what do most of the clones develop into?
Most of the clones will develop into short-lived plasma cells that produce large quantities of specific antibody
- what will a small proportion of the clones develop into?
A small proportion of clones will differentiate into long-lived memory cells that function to provide long-term immunity
Do pathogens only contain one antigenic fragment? Why?
Pathogens typically contain multiple distinct antigenic fragments on their surface and hence a single pathogen is likely to stimulate several different T and B lymphocytes to produce a variety of specific antibodies (polyclonal activation)
What happens when a specific B lymphocyte is activated?
When a specific B lymphocyte is activated following antigen presentation, it divides into plasma cells and memory cells
What are plasma cells?
Plasma cells are short-lived and secrete high numbers of antibodies that are specific to a particular antigen
What do plasma cells secrete?
Plasma cells will secrete ~ 2,000 antibody molecules per second into the bloodstream for roughly 4 to 5 days
By what mechanisms can antibodies aid in the destruction of pathogens?
Precipitation
Agglutination
Neutralisation
Inflammation
Complement activatio
mnemonic : PANIC