Immune response

Specific, non specific and antibodies.

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Immune response
Non ­ specific responses
Primary defences:
Skin ­ most skin cells are called Keratinocytes, these cells act as a barrier to pathogens.
Mucous membranes - Mucus (made in the goblet cells) trap pathogens then is expelled out
of the body.
Stomach ­ very acidic environment and this kills the pathogens.
Secondary defence:
Phagocytes engulf and destroy pathogens.
It recognises pathogens by their antigens on their surface.
Antibodies in our blood attach to the antigens, phagocytes have membrane bound protein
that act as receptors.
Lysosomes (inside the phagocyte) release digestive enzyme (lysins) to digest the pathogen.
The phagocyte then absorbs the harmless products of digesting the pathogen.
Specific immune response
Responding to the antigen on the surface of the pathogen
3 ways the antigen can be recognised by the immune system:
1. On the surface of pathogen once in the body
2. Some phagocytes (macrophages) engulf pathogen and present the antigens on their surface
(antigen presentation)
3. Infected cells may also put antigens from the pathogen on their cell surface
Antigens are recognised by:
T-helper cells ­ signal to other WBC by releasing chemicals called cytokines.
T-killer cells will destroy host infected cells to destroy pathogens before multiplying.
B-cells ­ the specific cells identified (clonal selection) which have the correct version of the
receptor for the antigen on the infecting pathogen. This specific t/b cell then divides by
mitosis into a large no. of identical cells = clonal expansion.
B-cells divide and then differentiate into b-plasma cells which make antibodies which are
specific to the antigen.
B-memory cells stay in the blood so when the same antigen is detected they can become
plasma cells and quickly respond by producing antibodies.
T-memory cells also remain in the blood to trigger the b-cell response.

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Antibodies
made of protein
4 polypeptide chains (2 heavy & 2 light/short)
Disulfide bridges between the coils of the antibody (tertiary structure)
Antibodies attach to antigen to neutralise the pathogen.…read more

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