CBI-20306 Cell biology and health reader
summary
1- Introduction to the immune system
Foreign invaders include:
Bacteria
Viruses
Parasites
Fungi
When the immune system does not function properly it can target the wrong thing causing allergies
and autoimmune diseases. Cytokines allow cells to regulate their own growth and behaviour, enlist
their fellows and direct new recruits to trouble spots.
A pathogen can enter the body through skin or through mucous membranes. The three defense lines
are:
1. Physical barriers
2. Innate immune system
3. Adaptive immune system
The key to the immune system is to distinguish between the self and non-self. This distinction is
made via peptide presentation on MHC complexes. MHC complexes that carry foreign molecules
kick-start the immune system.
An antigen is anything that triggers an immune response. A seemingly harmless substance to which
the immune system responds is called an allergen.
All immune cells originate from stem cells in the bone marrow. Leukocytes are divided in
mononuclear cells and granulocytes.
Mononuclear include:
Monocytes
Lymphocytes
NK cells
Granulocytes include:
Neutrophils
Eosinophils and basophils
Mast cells are special cells that can only be found in tissue and not in the blood. They have a central
oval nucleus and histamine granules
Monocytes
Have an irregular shape and kidney shaped nucleus
Actively leave the blood stream and morph into macrophages
When they encounter a pathogen, they phagocytose. A phagosome fuses with a lysosome
and the chemicals destroy the pathogen
Lymphocytes
Small, almost filled by the nucleus
When activated cytoplasm increases
Can become a T or B cell in either thymus or bone marrow. B cells start producing antibodies.
T cells further differentiate
,NK cells
Short lived
Mostly in blood, spleen or liver
Neutrophils
Lobed nucleus (3) and many small granules
Kill by phagocytosis
Move into tissue when called
Short lived
Eosinophils
Lobed nucleus (2) and granules in cytoplasm
Involved in protection from parasites
When a parasite is too large to phagocytose, they excrete their granules to create a toxic
environment
Basophils
Lobed nucleus (2) and large granules
Can protect from parasites through degranulation
Mast cells
Look like basophils but don't occur in the blood
Central oval shaped nucleus
Long lived
Phagocytose opsonized bacteria
Stores histamine in granules
Takes part in allergic reactions
All cells have proteins on their surface called 'cluster of differentiation' CD molecules. Helper T cells
have CD4 on their membrane.
Immune response:
1. A cut in a finger
2. Activation innate immune system
3. Neutrophils present become activated
4. They release granules with bacteria killing enzymes
5. Some neutrophils can explode to create a sticky web trapping bacterium
6. Macrophages arrive and seek out bacteria and eat dying neutrophils
7. Macrophages phagocytose bacteria and kill them by releasing chemicals into the phagosome
8. The macrophage releases chemicals and cytokines which increase blood flow to the cut
9. The macrophage releases cytokines alerting other cells
10. The adaptive immunity is activated
Cytokines
Include interleukins, interferons and growth factors
Most interleukins are produced by t helper cells
Il-2 triggers the immune system to produce t cells
Chemokines generally attract specific cell types
Cytokines can be pro-inflammatory or anti-inflammatory
Cytokines can have different effects/multiple roles at different sites
Antibodies
, Produced by activated B cells
Consists of 2 heavy and 2 light chains
Tips (Fab-fragments) are highly variable and are binding sites
The tail is referred to as the Fc site
A pathogen consists of multiple antigens
an epitope can be a PAMP specifically recognized by receptors on immune cells, each
antibody is specific for one epitope
Antibody functions are:
o Neutralization of the pathogen by covering it
o Opsonisation (flagging it/labelling it)
o Complement activation
Antibodies bind to the Fab parts; Fc receptors bind to the Fc part of antibodies. Fc receptors
can have an activating or inhibiting function
Adaptive immunity can be a cellular or humoral response.
2- structure of the immune system
There are primary and secondary lymphoid organs. At primary sites immune cells are created.
Cut example from Ch. 1 activation adaptive immunity:
1. Monocyte derived cells take up an antigen and travel to secondary lymphoid organs
2. The antigen is presented to the adaptive immune system
In primary lymphoid organs a process occurs that destroys 95% of the self-antigens.
Bone marrow
Lymphocytes derived from here are B cells
Contains two types of stem cells
o Hematopoietic (blood cell producing)
o Stromal (fat/cartilage/bone producing)
Two types of bone marrow
o Red
o Yellow
Most blood cells originate from red marrow which mainly occurs in flat bones like hip bones
Thymus
Lymphocytes that mature here are T cells
Incorrect T cells or ones that attack the 'self' die and are removed
After puberty involution of the parenchyma of the thymus occurs
Each thymus lobe is divided into a dark peripheral cortex and a lighter central medulla.
Lobes contain reticular cells, macrophages and lymphocytes
Reticular cells from a network providing support. They help maintain a microenvironment
Lymphocytes are more numerous in the cortex
In the thymus positive and negative selection for T cells occurs
Infection from the skin is managed by lymph nodes, infections from the intestine is managed by
peyers patches. Blood borne pathogens are taken care of by the spleen and respiratory infections go
to organs like the tonsils. Each lymphoid organ provides a microenvironment appropriate for the
pathogen that will be encountered there.
Lymph nodes
summary
1- Introduction to the immune system
Foreign invaders include:
Bacteria
Viruses
Parasites
Fungi
When the immune system does not function properly it can target the wrong thing causing allergies
and autoimmune diseases. Cytokines allow cells to regulate their own growth and behaviour, enlist
their fellows and direct new recruits to trouble spots.
A pathogen can enter the body through skin or through mucous membranes. The three defense lines
are:
1. Physical barriers
2. Innate immune system
3. Adaptive immune system
The key to the immune system is to distinguish between the self and non-self. This distinction is
made via peptide presentation on MHC complexes. MHC complexes that carry foreign molecules
kick-start the immune system.
An antigen is anything that triggers an immune response. A seemingly harmless substance to which
the immune system responds is called an allergen.
All immune cells originate from stem cells in the bone marrow. Leukocytes are divided in
mononuclear cells and granulocytes.
Mononuclear include:
Monocytes
Lymphocytes
NK cells
Granulocytes include:
Neutrophils
Eosinophils and basophils
Mast cells are special cells that can only be found in tissue and not in the blood. They have a central
oval nucleus and histamine granules
Monocytes
Have an irregular shape and kidney shaped nucleus
Actively leave the blood stream and morph into macrophages
When they encounter a pathogen, they phagocytose. A phagosome fuses with a lysosome
and the chemicals destroy the pathogen
Lymphocytes
Small, almost filled by the nucleus
When activated cytoplasm increases
Can become a T or B cell in either thymus or bone marrow. B cells start producing antibodies.
T cells further differentiate
,NK cells
Short lived
Mostly in blood, spleen or liver
Neutrophils
Lobed nucleus (3) and many small granules
Kill by phagocytosis
Move into tissue when called
Short lived
Eosinophils
Lobed nucleus (2) and granules in cytoplasm
Involved in protection from parasites
When a parasite is too large to phagocytose, they excrete their granules to create a toxic
environment
Basophils
Lobed nucleus (2) and large granules
Can protect from parasites through degranulation
Mast cells
Look like basophils but don't occur in the blood
Central oval shaped nucleus
Long lived
Phagocytose opsonized bacteria
Stores histamine in granules
Takes part in allergic reactions
All cells have proteins on their surface called 'cluster of differentiation' CD molecules. Helper T cells
have CD4 on their membrane.
Immune response:
1. A cut in a finger
2. Activation innate immune system
3. Neutrophils present become activated
4. They release granules with bacteria killing enzymes
5. Some neutrophils can explode to create a sticky web trapping bacterium
6. Macrophages arrive and seek out bacteria and eat dying neutrophils
7. Macrophages phagocytose bacteria and kill them by releasing chemicals into the phagosome
8. The macrophage releases chemicals and cytokines which increase blood flow to the cut
9. The macrophage releases cytokines alerting other cells
10. The adaptive immunity is activated
Cytokines
Include interleukins, interferons and growth factors
Most interleukins are produced by t helper cells
Il-2 triggers the immune system to produce t cells
Chemokines generally attract specific cell types
Cytokines can be pro-inflammatory or anti-inflammatory
Cytokines can have different effects/multiple roles at different sites
Antibodies
, Produced by activated B cells
Consists of 2 heavy and 2 light chains
Tips (Fab-fragments) are highly variable and are binding sites
The tail is referred to as the Fc site
A pathogen consists of multiple antigens
an epitope can be a PAMP specifically recognized by receptors on immune cells, each
antibody is specific for one epitope
Antibody functions are:
o Neutralization of the pathogen by covering it
o Opsonisation (flagging it/labelling it)
o Complement activation
Antibodies bind to the Fab parts; Fc receptors bind to the Fc part of antibodies. Fc receptors
can have an activating or inhibiting function
Adaptive immunity can be a cellular or humoral response.
2- structure of the immune system
There are primary and secondary lymphoid organs. At primary sites immune cells are created.
Cut example from Ch. 1 activation adaptive immunity:
1. Monocyte derived cells take up an antigen and travel to secondary lymphoid organs
2. The antigen is presented to the adaptive immune system
In primary lymphoid organs a process occurs that destroys 95% of the self-antigens.
Bone marrow
Lymphocytes derived from here are B cells
Contains two types of stem cells
o Hematopoietic (blood cell producing)
o Stromal (fat/cartilage/bone producing)
Two types of bone marrow
o Red
o Yellow
Most blood cells originate from red marrow which mainly occurs in flat bones like hip bones
Thymus
Lymphocytes that mature here are T cells
Incorrect T cells or ones that attack the 'self' die and are removed
After puberty involution of the parenchyma of the thymus occurs
Each thymus lobe is divided into a dark peripheral cortex and a lighter central medulla.
Lobes contain reticular cells, macrophages and lymphocytes
Reticular cells from a network providing support. They help maintain a microenvironment
Lymphocytes are more numerous in the cortex
In the thymus positive and negative selection for T cells occurs
Infection from the skin is managed by lymph nodes, infections from the intestine is managed by
peyers patches. Blood borne pathogens are taken care of by the spleen and respiratory infections go
to organs like the tonsils. Each lymphoid organ provides a microenvironment appropriate for the
pathogen that will be encountered there.
Lymph nodes
