IMMUNITY
immunity
Phagocytes (neutrophils + macrophages)
• originate in bone marrow
• they are scavengers -remove any dead cells and invasive
organisms
Neutrophils
• have a lobed nucleus and granular cytoplasm
• short lived cells
Macrophages
• larger than neutrophils
• travel In blood as monocytes which develop into macrophages
once they leave the blood and settle in organs, where they
remove foreign matter
• long-lived cells
• do not destroy pathogens completely, they're cut up and their
antigens are displayed, hence it becomes an antigen presenting
cell.
Phagocytosis
• during an infection (caused by pathogens
invading the body), cells under attack respond
by releasing chemicals called histamines
• these attack neutrophils
• the movement towards chemical stimulus is
called chemotaxis
General steps of phagocytosis:
1) attraction (chemotaxis)
2) recognition + attachment
3) endocytosis
4) bacteria trapped within phagocytotic vacuole
5) fusion of lysosomes and phagocytotic vacuole
6) killing and digestion
lymphocytes
T-cells
B-cells 1. T-helper
1. B-plasma 2. T-killer
2. B-memory 3. T-memory
B-cells T-helper
-made and mature in the bone marrow produce interleukins
-travel to spleen for final maturation Interleukins stimulate:
1) B-plasma cells 1) B-cells to make antibodies
short lived 2) other T-cells to divide
3) macrophages to enhance the effect of
produce antibodies phagocytosis
2) B-memory cells T-Killer
form the immunological memory of destroys cells by releasing perform which
the body makes holes in the cell surface membrane
responsible for secondary response
T-memory
leads to immunological memory of antigen
responsible for secondary response.
cell mediated immunity
1) macrophage engulfs pathogen
2) T-helper's cell receptors, which is complementary to antigen, binds to antigen
3) T-helper then releases Interleukins
Interleukins stimulate B-cells to divide into plasma cells and produce antibodies in the humoral response.
Clonal selection - process by which an antigen binds to and activates Only those lymphocyte
bearing receptors for the antigen.
(in short, this is basically recognizing and choosing which B-cells to use)
Clonal expansion - the rapid multiplication of Bori)cell clones after activation by an antigen
numbers of white blood cells
• neutrophils in the blood increases during bacterial infection and whenever tissues become
inflamed and die.
• lymphocyte numbers increase during viral infections and TB.
Immune response - the complex series of responses of the body to
the entry of a foreign antigen
Involves activity of lymphocytes and phagocytes
antigen -substance that is foreign to the body and stimulates an
Immune response
self antigen - substance produced by the body that the Immune system does not recognise as foreign
and therefore does not stimulate an immune response.
non-self antigen - any substance or cell recognized by the immune
system as foreign and stimulates an immune response.
role of memory cells in the long-term
remain in blood for years and cause long term protection
antibodies
• globular glycoproteins
• have quaternary structure
• form group of plasma proteins called Immunoglobulins
hinge region -gives flexibility to bind around antigen
antigen binding sites - sequence of amino acids In
these regions make specific 3D shape which binds to
one type of antigen
functions of antibodies
- attach to flagella of bacteria making them less active and
easier for phagocytes to engulf
- cause agglutination (clump together)of bacteria reducing chance of spread
- punch holes in bacteria cell walls, causing them to burst when they absorb
water by osmosis
- antibodies coat bacteria, making phagocytosis easier as phagocytes have
receptor proteins
- combine with toxins, neutralizing them
- combine with viruses and bacterial toxins preventing them from entering or
damaging tells
-
Hybridoma method for the production of monoclonal antibodies
• B cells that divide by mitosis do not produce antibodies and plasma cells that secrete antibodies
do not divide
• Monoclonal antibodies - identical copies of one type of antibody
1) Antigen is injected into mouse
2) Spleen cells produce lymphocytes which produce antibodies are removed
3) plasma cells from spleen are fused with cancer cells or myeloma cells
forming hybridoma cells that divide indefinitely.
4) they divide by mitosis and produce antibodies
Using monoclonal antibodies in diagnosis and treatment of disease
In diagnosis
• used to locate position of blood clots
• Used to locate cancer cells which have different cell surface proteins and therefore can be
detected by antibodies
• Used to identify the strain of virus or bacterium causing an infection, which speeds up treatment
In treatment
• treatment of breast cancer - antibody binds to cancerous cells and marks them for destruction
by immune system
• Treatment of rheumatoid arthritis- antibody binds to proteins secreted by T-cells that causes
damage to cartilage in joints and blocks it's action
Types of immunity
Immunity
Active immunity Passive immunity
an antigen enters the Immunity gained
body, an immune without an
response occurs, and immune response
antibodies produced in
plasma.
Natural Artificial
• gained by being • gained by
infected (active) vaccination (active)
• mother to baby • Injecting antibodies
across placenta or (passive)
breastmilk (passive)
Vaccines
• preparation containing antigens which is used to stimulate an immune response artificially
• it may contain antigens in the form of live or dead microorganisms, harmless (attenuated
organism), toxoid (harmless toxin), surface antigens
How do vaccines provide long term immunity?
1) vaccines contains antigen that stimulate immune response
2) macrophages take up virus by phagocytosis and act as antigen presenting cells
3) lymphocytes bind to these and under clonal selection
4) clonal expansion then occurs by mitosis
5) memory cells are formed
6) booster is used to further stimulate memory cell formation
Poor response to vaccinations due to
• suffer from malnutrition and don't have enough proteins to make antibodies or
clones of lymphocytes
• Defective immune system and don't develop necessary B and T cell clones
Herd immunity
• herd immunity interrupts transmission in a population so that those who are susceptible
never encounter the infectious agents concerned
