Cell regognition and the immune system Flashcards
What are our defence mechanisms against pathogens?
Preventing entry of pathogens,
Physical and chemical.
Inflammation (swelling and heating) the region incaded by the pathogen
recognising ‘foreign’ cells and targeting any pathogenic cells - specific immune response.
What can the immune response identify?
Pathogens
Cells from other organisms of the same species
Abnormal body cells
toxins
What is an antigen
Marker molecules that can be detected by antibodies and trigger an immune response.
What is the importance of antigens in the immune response?
Phagocytes have surface protiens - act as receptors
bind to antigens
engulf and digest
presented on surface of phagocyte (now antigen presenting cell)
specific immune response triggered.
Antigen variability
antigens on the surface of a pathogen changing frequently due to genetic
mutations
Problem - SPECIFIC immune response does not work as it is only complememtry in shape to one antigen.
when the pathogen changes - lymphocytes and memory cells can no longer bind.
no secondary immune response. host infected and suffers again.
Phagocytes immune response type and two types.
Non-specific.
Neutrophils
Macrophages
Neutrophils, function
released in large numbers but short lived
chemicals released by the pathogens attract the neutrophils
this response is known as chemotaxis
the pathogen they are travelling to many be covered in antibodies.
these antibodies will stimulate an attack.
Receptor protiens recognise antibody molecules and attach to them.
cell surface membrane engulfs the pathogen in a phagocytic vacuole.
endocytosis.
What is the job of lysosomes in the immune response?
contain lysozymes
digest unwanted material in the cells.
the phagocytic vacuole around the pathogen is called a phagosome
a lysosome fuses with the membrane of the phagosome to form a phagolysosome
digestive enzymes released and destroy the pathogen. After killing and digesting the pathogens, neurophils die, this leads to the formation of Pus.
What is endocytosis?
engulfing a cell using the cell membrane to bring it into the cell.
Macrophages role in the immune system
larger than neutrophils and are long lived cells
in organs (lungs, liver, spleen, kidney) not just the blood
monocytes turn into macrophages when they leave the blood.
do not destroy the pathogens completely, cut it up.
display the antigens on their surface
to be recognised by lymphocytes.
T lyphocytes compared to phagocytes
Both white blood cells
specific immune response rather to non-specific
smaller
both produced in the bone marrow
The T-lymphocyte response.
T-cell receptors
similar structure to antibodies and are each specific to one antigen.
activated by binding to their specific antigen which is presented
this antigen presenting cell is a macrophage.
displaying the antigen on it’s cell surface membrane.
Divide by mitosis
Helper T cells
Cytotoxic T cells.
Role of Helper T cells.
Release cytokines (hormone-like signals)
stimulate:
maturation of B-lymphocytes into antibody secreting plasma cells
production of memory B cells
activation of cytotoxic T cells
increased rate of phagocytosis
B-lymphocytes and the humoral immune response
each B-lymphocte can only make one type of antibody molecule
part of each antibody forms a glycoprotien receptor which combines with specifically one type of antigen.
They recognise the pathogen, bind to it (clonal selection)
divid repeatedly by mitosis (clonal expansion)
they can differentiate into:
plasma cells
memory cells
Primary immune response
clonal selection
Clonal expansion
plasma cell B-lymphocytes secrete lots of atibody molecules
short lived but antibodies stay longer than the cells.
memory B-lymphocyte cells remain circulating the blood for a long time.
Relatively slow process
