cell recognition and the immune system Flashcards
physical and chemical defense of the human body
first line of defense
skin, mucous, tears, saliva, inflammation, recognizing foreign cells to be targeted
how does the body recognise foreign cells
proteins on the surface of cells and viral particles allow them to be identified
often part of the phospholipid biolayer - glycolipids and proteins
function of proteins on the surface of cells
allows the body to recognise self and foreign cells
what types of cells are foreign
pathogenic cells
abnormal body cells
toxins
name of the molecule used by the body to identify foreign cells
antigen
examples of the importance of antigens
(phagocytosis)
phagocytes have surface proteins that act as receptors and bind to the proteins on the surface of pathogens
this means that pathogens can be ungulfed
the antigens that were in the pathogen can now be presented on the phagocyte
other cells of the immune system can then be recruited
ultimately what is the purpose of antigens
cell to cell recognition
self antigens definitiuon
antigens that are produced by the organisms own body cells
dont stimulate immune response
how do pathogens have antigen variability
antigens on their surface changes frequently due to genetic mutations
why is antigen variability bad
surface receptors on memory cells can only bind to one antigen so no secondary immune responses can form
role of phagocytes
recognise and engulf pathogens - phagocytosis
phagocytosis process
chemicals released by the pathogens attract phagocytes
phagocytes move toward the site of infection, non self antigens recognised
phagocyte binds to antigens on pathogen
cell membrane of phagocytes extends out entrapping the pathogen in the phagocytic vacuole
lysosome fuses with the phagocytic vacuole
hydrolytic enzymes digest the pathogen
pathogen us displayed on the cell surface
What type of cell are lymphocytes
White blood cell
Features of lymphocytes
Smaller than phagocytes
Large nucleus
Produced in the bone marrow
Life cycle of T - lymphocytes
Immature t lymphocytes form in the bone marrow
They leave the bone marrow to mature in the thymus
When they mature they develop T-cell receptors (basically an an antigen)
How do T cells divide
Mitosis
How do T-lymphocytes activate
When they encounter and bind to a specific antigen that is being presented by host cells
This could be a phagocyte
What happens when T lymphocytes activate
Divide by mitosis to increase in number
They then differentiate into :
Helper T cells
Cytotoxic T cells
What does an antigen presenting cell do
Present the antigens from toxins, ingested pathogens and foreign cells
Help to recruit other cells of the immune system
Specific immune response can be created
Many immune system cells can present antigens - examples
Macrophages and dendritic cells
Function of helper T cells
Assist other white blood cells in the immune response by releasing cytokines which stimulate :
Maturation of B lymphocytes into antibody secreting plasma cells
Production of memory B cells
Activation of cytotoxic T cells which destroy tumour cells
Killer T cells function
Patrol the body in search of antigen presenting cells
Attach to the foreign antigens on the cells membrane of infected cells
Secrete toxic substances that kill the infected body cells and the pathogen inside
What do B lymphocytes do
Mature the genes coding for antibodies
Once mature B lymphocyte cells make one type of antibody molecule - these remain on the cell surface membrane of the molecule
Part of each antibody forms a glycoprotein receptor that can combine specifically with one type of antigen
What must b cellss (when immature) do before developing antibody receptors
Divide by mitosis
Process of a primary immune response using B lymphocytes
Only one b cell has an antibody receptor that is specific to the shape of the antigen that has entered the body
The selected b cell divides by mitosis, some of the daughter cells develop into plasma cells others into memory cells
Plasma cells secrete antibodies that specifically combine with the antigen that has entered the body
