Can you describe how each
type of cell has speci c CELL RECOGNITION AND THE
molecules on its surface that
identify it ?
These speci c molecules include proteins and
IMMUNE RESPONSE
enable the immune system to identify:
• pathogens Can you describe the effect on antigen variability on disease and disease
• cells from other organisms of the same prevention ?
species Antigen variation is where the antigen on the surface on the pathogen are formed differently due to changes in the
• abnormal body cells gene of the pathogen .
• toXins This means when your infected a second time , the memory cells from the rst infection will not recognise the
antigens and the immune process has to start from scratch
Can you de ne antigen ?
EG. HIV and u virus
Any part of organism that is foreign
and triggers the attack of antibodies in
the immune system Can you describe the role of antigen presenting cells in the cellular response ?
• when pathogens invade body cells or are taken in by phagocytosis, the phagocyte places antigens from the
Can you de ne antibody ? pathogen on its cell-surface membrane.
Protein that is produced by lymphocytes and • receptors on a speci c helper T cell t exactly onto these antigens.
attaches to a speci c antigen • this activates the T cell to divide rapidly by mitosis and form a genetically identical clone of itself.
• the cloned T cells are then able to develop into memory cells that enable rapid response to future infections by the
same pathogen, as well as stimulate phagocytes to engulf pathogens by phagocytosis, B cells to divide and secrete
their antibody and activate cytotoxic T cells.
Can you explain the Can you describe the role of helper T cells
concept of herd in stimulating :
immunity ? Cytotoxic T cells - Helper T cells divide and
Can you describe the structure • if three quarters of a differentiate through mitosis into cytoxic T cells .
of an antibody ? population are vaccinated ,
B cells - helper T cells stimulate B cells to divide into
• heavy and light chain the occurrence of the
• Variable and constant region disease is reduced. plasma and memory cells.
• Binding site • Therefore those not Phagocytes - stimulates phagocytes to engulf
• Disulphide bridge vaccinated have a fewer pathogens by phagocytosis
chance of catching it.
Can you describe the response of T lymphocytes
to a foreign antigen ( the cellular response )
• Phagocyte engulfs pathogen and displays antigen on cell surface.
• A T cell with a speci c receptor binds onto the antigen
• T cell divides through mitosis into T helper cells, Cytoxic and
memory cells
• Cytoxic cells release perforin which destroys cells surface membrane
.
Can you explain phagocytosis ?
• Phagocyte recognises the foreign antigens
• Cytoplasm moves around the pathogen , engul ng it.
• Lysosomes fuse with phagocyte vacuole , lyzozomes kill the pathogen
• The phagocyte then presents the pathogens antigens , activating
other immune system cells.
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, Can you describe the response of B
lymphocytes to a : Describe the role of :
foreign antibody ( Humerol immunity )- T helper cells - release chemical signals
• Antigen binds to complimentary B cell receptor that stimulate phagocytes , cytoxic cells and B
• Antigen is engulfed and digested by the B cell cells .
• Antigen is presented on plasma membrane Cytotoxic T cells - release perforin which
• T cell binds to antigen , stimulating B cells to divide by
mitosis destroys cells surface membranes , killing them.
• B cells differentiates , into plasma and memory cells
Clonal Selection - B cells - responsible for Humerol response ,
When an antigen binds to an antibody on the surface of a B divide into plasma and memory cells
cell , this together with the substances released from T helper
cells activates the B cell.
Memory cells - record the speci c
Can you explain the antibodies needed to bind to the antigen and
formation of the remain in blood.
Describe the roles of plasma and memory antigen-antibody
cells in the primary and secondary complex ? Plasma cells - Identical clones of B cells
immune response - When an antigen and which secrete lots of antibodies
Primary : slow response as not enough B cells to antibody have the
make antibodies ,eventually makes enough antibodies complimentary molecular
shape .
then T and B cells produce memory cells. When a antibody collides
Secondary : clonal selection happens faster , with a complimentary
memory cells divide into plasma cells to produce antigen they bring forming Cell mediated - T cells and other immune
antibodies , memory T cells divide into cytoxic T cells to an antigen antibody system cells used
kill the cell carrying antigen. complex
Humerol response - B cells , clonal
selection and production of monoclonal
Can you describe the structure of HIV
( human immunode ciency virus)
• core contains RNA and reverse transcriptase
• Outer counting of a capsid and extra layer called
an envelope ( stolen from previous host cell )
• Sticking out the envelope are lots of attachment
Can you explain the differences between proteins
active and passive immunity ?
Active - when your immune system makes its won Can you describe HIVS replication in
antibodies after being stimulated by a antigen
helper T cells
• attachment protein attaches to cell membrane
Passive -immunity you get from being given antibodies • Capsid releases into cells , released RNA into
made by a different organism . cytoplasm
• Reverse transcriptase used to make
Passive immunity natural - baby becomes immune due to complimentary DNA strand from RNA template
antibodies in breast milk • Double stranded DNA made from this inserted
Passive immunity arti cial - you become immune after being into human DNA
injected with antibodies from something else • Host cells enzymes used to make viral proteins
Active immunity natural - when you become immune after from viral DNA found in human DNA
catching the disease • Viral proteins assemble into new virus which buds
Active immunity arti cial - when you become Immune after from cells and go on infect other cells.
being given the vaccine .
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