5.1- DEFENCE MECHANISMS Flashcards
What is any infection, in effect?
interaction between the pathogen and the body’s various defence mechanisms
How can an individual die from a pathogen sometimes?
sometimes the pathogen overwhelms the defences
How can the body recover from a disease?
body’s defence mechanism overwhelms pathogen and individual recovers
How does the body overcoming a pathogen help it for next time?
body’s defences are better prepared for same pathogen + can kill it before it can cause any harm
What is the body being able to kill the pathogen before it causes harm called?
immunity
What is the main reason for why some people are unaffected by certain pathogen?
immunity
Who will rarely die from an infection?
fit, healthy adult
Who is more likely to die from an infection?
ill health, young and elderly usually more vulnerable
What does the human body have to protect itself from pathogens?
range of defences
What are the two types of defences the human body has?
general and immediate defences
more specific, less rapid but longer-lasting
Examples of general and immediate defence? (2)
skin forms barrier to entry of pathogens
phagocytosis
What do more specific, less rapid but longer-lasting response involve?
a type of white blood cell called a lymphocyte
What two forms do more specific, less rapid but longer-lasting response take?
cell-mediated responses
humoral responses
What do cell-mediated response involve?
T lymphocytes
What do humoral responses involve?
B lymphocytes
What must lymphocytes be able to do to defend the body from invasion by foreign material?
distinguish body’s own cells + molecules from those that are foreign
What are the body’s own cells + molecules called?
self
What are foreign material called?
non-self
What would lymphocytes do if they were unable to distinguish body’s own cells + molecules from those that are foreign?
lymphocytes would destroy organism’s own tissues
What does each type of cell, self or non-self have?
has specific molecules on its surface that identify it
What is most important about the molecules (cells, self + non-self)?
proteins
Why are the proteins the most important (cells, self + non-self)?
proteins have enormous variety + a highly specific tertiary structure
What does the variety of specific 3D structure do? (cells, self + non-self)?
distinguished one cell from another
What does the protein molecule allow the immune system to identify? (4)
pathogen i.e. HIV
non-self material i.e. cells from other organisms of same species
toxins including those produced by certain pathogens like bacterium that causes cholera
abnormal body cells i.e. cancer cells
As pathogens, non-self material, toxins and abnormal body cells are all potentially harmful, what is the first stage of removing the threat they pose?
identification
What complications can human who have had tissue/organ transplants have?
immune system recognises these as non-self even though they have come from individuals of same species
What does the immune system try and do to transplanted tissue/organ?
attempts to destroy the transplant
What is done to reduce the tissue rejection?
donor tissues for transplant normally matched as closely as possible to those of recipient
Where do the best matches for tissue-organ transplants come from?
often come from relatives that are genetically close
What are administrated to patients after organ/tissue transplants?
immunosuppressant drugs
What do immunosuppressant drugs do?
reduce level of immune response that still occur
Are specific lymphocytes produced in response to an infection?
no
Do all specific lymphocytes already exist?
yes- all 10 million different types
Given that there are so many different types of lymphocytes, what does this mean when a pathogen enters the body? (hint: probability?)
high probability that when a pathogen gets into the body, one of these lymphocytes will have a protein on its surface that’s complementary to one of the proteins of the pathogen
In other words, what happens when the lymphocyte has a protein on its surface that’s complementary to one of the proteins on the pathogen?
lymphocyte will ‘recognise’ the pathogen
As there are so many different lymphocytes, what are the numbers like of each type?
there are very few of each type
As there are very few of each type of lymphocyte, what happens when an infection occurs?
the one type already present that has the complementary proteins to those of the pathogen stimulated to divide to build up its numbers
Why does the one type of lymphocyte already present that has a complementary protein to those of the pathogen divide and build its numbers?
so it has numbers to a level where it can be effective in destroying it
What is it called when the complementary lymphocyte to the pathogen divides to destroy it?
clonal selection
What does clonal selection explain?
why there’s a time lag between exposure to the pathogen and body’s defences bringing it under control
About how many different lymphocytes are present at any time?
around 10 million
What is each type of lymphocyte capable of?
capable of recognising a different chemical shape
In the foetus, what are the lymphocytes constantly doing?
constantly colliding with other cells
Why is infection in a foetus rare?
because it’s protected from the outside world by the mother, and in particular, the placenta
As infection in a foetus s rare, what will the lymphocytes collide with?
collide almost exclusively with the body’s own material (self)
What will some of the lymphocytes have?
receptors that exactly fit those of the body’s own cells
What happens to the lymphocytes that have receptors that fit those of the body’s own cells?
either die or are suppressed
What are the remaining lymphocytes like, after the lymphocytes with receptors that fit the body’s won cells are removed?
only remaining lymphocytes are those that might fit foreign material (non-self) and so only respond to foreign material
What do lymphocytes produced in the bone marrow in adults initially only encounter?
only encounter self-antigens
What happens to lymphocytes from the adult bone marrow that show an immune response to the self-antigens?
undergo programmed cell death (apoptosis) before they can differentiate into mature lymphocytes
Will any clones of the anti-self lymphocytes appear in the blood?
no
What is left as the clones of the anti-self lymphocytes do not appear in the blood?
leaves only those that might respond to non-self antigens
