Immunity - B cells and antigenic variability

AQA - immunity

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B-cells and humeral immunity
First phase of the immune response is the cloning of T-cells. To allow them to build up their
T-cells produce factors that stimulate the B-cells to divide
B cells are responsible for the next stage in the immune response
This is called the humeral response.
This is because it involves antibodies
Antibodies are soluble in blood and in tissue fluids
Another word for bodily fluids is humour
There are many different types of B cells
As many as 10 million
Each of these 10 million produce a different antibody
Each antibody responds to one specific antigen
Protein on the surface of the of the pathogen cell Enters the blood or the tissue fluid 1
type of B cell has an antibody on it that is specific It fits the antigen ... they are
complimentary The B cell divides by mitosis Which forms a clone of B-cells Which
produces an antibody which is specific to the antigen.
They typical pathogen of TB has many different types of proteins on its surface They
all act as antigens Some pathogens, for example Cholera also produce toxins These
toxins also act as antigens --. Therefore, many different types of B cells make clones
The cell developed into 1 of 2 types of clones
A) Memory cells
B) Plasma Cells
Plasma cells secrete antibodies directly
They survive only for a few days
But make 2000 antibodies per second during their lifespan
Antibodies destroy pathogens and the toxins that they have produced
Plasma cells are responsible for immediate defence against infection
This is known as the primary immune response
Memory cells live longer than plasma cells
They live for decades
They do not produce antibodies directly, but circulate in the blood
If they encounter some pathogen at a later rapidly divide and become plasma cells
plasma cells produce the antibodies needed to destroy the pathogen while new memory
cells circulate in readiness for future infection. This is known as the secondary immune
It is more rapid and of grater intensity than the primary response
It ensures that the new infection is repulsed before it can cause any harm
Individual is usually unaware that they are having an infection.
When you get infected with chicken pox ... you get it once and then you are immune to it
for the rest of your life. This is because these diseases are single types. And thus, quickly
identified when they enter our body on the subsequent occasions.
In contrast influenza virus has over 100 different strains

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Antigens that the virus is made out of and those that produce the antigens are constantly
This is known as antigenic variability
This leads to the primary immune response
Body reacts as if it is a new infection
And so we get ill.…read more


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