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Antibody Structure and Function
The immune response
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Antigen
Molecule found on the
cell surface membrane
that can be
recognised as foreign
by the immune system.
Usually proteins,
glycoproteins or
glycolipids.
Antibody
(Immunoglobulin)
Proteins with a
specific quaternary
structure.
Able to bind
specifically to
antigens.
Produced by B-cells.
Antibody structure
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Antibody Structure
The specificity of the
antibody depends on its
variable regions
Antigen
Variable
regions (red)
The constant
regions are the
same for all
antibodies
Light chain
Hinge region
Disulphide bridges
Heavy chain
Constant regions
(blue)
Each antibody has a different shaped variable region (due to different amino acid
sequences) that is complementary to one specific antigen.
Antigen
binding
site
Antigen
binding
site
The structure
of an antibody
All antibodies are proteins. This means that they are made up of a long
chain of amino acids which are arranged into a complex structure.
Effector mechanisms
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Now try the questions at the end of the sheet.
What are lymphocytes?
Lymphocytes are a type
of white blood cell
(leukocyte) found in the
blood and lymph nodes.
Lymphocytes recognise
antigen molecules on the
surface of pathogens, and
co-ordinate the immune
response against that
pathogen.
Collectively, lymphocytes can recognize millions of different
antigens, due to the large variation of lymphocytes produced.
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Humoral and Cellular Immune Responses
-
Involve lymphocytes
B-lymphocytes – mature in bone marrow
T-lymphocytes – mature in thymus
B-lymphocytes produce antibodies –
humoral response
- T-lymphocytes directly affect
cells – cellular response
Different types of lymphocytes
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Humoral immune response
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B-cells
B-cell binds to antigen.
B-cell divides by mitosis.
Some cells formed are plasma cells – secrete
antibodies.
Some cells formed are memory cells – remain
in blood for a period of time, providing
immunity.
B-cells
Cellular immune response
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T-cells
Phagocyte takes up pathogen.
Antigens presented on surface of phagocyte
(antigen-presenting cell).
T-cell binds to antigen on APC.
T-cell divides by mitosis.
Several types of T-cell produced, including
memory cells and cells that stimulate B-cells
to replicate.
T-cells