Cell recognition and the Immune system Flashcards
Name some of the bodies defence mechanisms against pathogens
Physical and chemical defences, Inflammation (swelling and heating) and recognising foreign cells known as ‘specific immune response’
Give examples of physical defences
Skin and Mucus Membranes
Give examples of chemical defences
Tears, saliva and sweat containing lysozyme, destroys bacteria
What is the name given to the bodies own cells
self
What is the name given to foreign cells
non-self
How can the body recognise foreign cells
Due to specific molecules located on the surface of cells (usually proteins)
What contains the surface molecules to be recognised as foreign
Pathogenic cells, abnormal body cells, toxins, cells from individuals from the same species
What are these surface molecules known as
Antigens
Give an example of abnormal body cells
Cancerous or pathogen infected cells
What form are toxins in
Chemical rather than cellular. (Released by bacteria)
Give an example of when cells from other individuals may enter the body
Organ transplants
What do antigens allow for
cell-to-cell recognition
Where do eukaryotes contain their antigens
Cell membranes
Where do prokaryotes contain their antigens
Cell walls
What can also act as antigens on cell surface membranes
Glycolipids and Glycoproteins
What are the two forms of antigen
Self antigens or Non-self antigens
What is antigen variability
Antigens present on the surface changing frequently due to genetic mutations.
Do some pathogens exhibit genetic variability
Yes
How does genetic variability pose as a problem for the immune system
Lymphocytes and memory cells produce one specific immune response. Therefore, the surface receptors are complementary in shape to just one antigen. When the antigen changes the lymphocyte and memory cells can no longer bind. So, no secondary immune response.
Give examples of common pathogens that exhibit antigen variability
The cold virus and influenza virus
What are the two main types of phagocyte
Neutrophils and Macrophages
What is the role of phagocytes
To recognise and engulf pathogens (phagocytosis)
What are phagocytes and where are they produced
White blood cells. Produced in bone marrow
What is the 1st step of phagocytosis
Chemicals released by pathogens, as well as chemicals released by body cells e.g. histamines, attract phagocytes. (Chemotaxis)
What is the 2nd step of phagocytosis
Phagocytes move toward the site of infection, where pathogens can be identified due to antigens. Phagocytes have receptor proteins on surface to recognise pathogens as non-self.
What is the 3rd step of phagocytosis
The phagocyte attaches to the pathogen by binding to its antigens. Once attached the cell surface membrane of the phagocyte extends our and around the pathogen engulfing it. (Endocytosis)
What is the phagocytic vacuole formed when the phagocyte engulfs the pathogen called
Phagosome
What is the 4th step of phagocytosis
The phagocytic vacuole fuses with a lysosome to form a phagolysosome. The lysosome releases digestive enzymes called lysozymes e.g. by hydrolysis of bacterial cell walls.
What is a lymphocyte
Another type of white blood cell
Which is smaller lymphocytes or phagocytes
Lymphocytes
What is the lymphocytes nucleus like
A large nucleus that fills most of the cell
When are lymphocytes produced
In the bone marrow before birth (weeks 25-32)
What are the two types of lymphocytes
T-Lymphocytes (T-Cells) and B-Lymphocytes (B-Cells)
Where do immature T - Lymphocytes mature
They leave the bone marrow and mature in the thymus
What do mature T - Lymphocytes have
T cell receptors
What is the structure of T cell receptors similar to
They are similar to antibodies and are specific to one antigen
When are T -Lymphocytes activated
When they bind to their specific antigen that is being presented by one of the hosts cells
How do activated T-lymphocytes divide
Mitosis
What two main types of T cell do T-Lymphocytes differentiate into
Helper T cells and Cytotoxic T cells (also known as killer T cells)
What do helper T cells do
Assist other white blood cells in the immune response by releasing cytokines which stimulate:
The maturation of B lymphocytes
The production of memory B cells
The activation of cytotoxic T cells
An increased rate of phagocytosis
What do T killer cells do
Patrol the body, attach to the foreign antigens on the cell surface membranes of infected cells and secrete toxic substances that kill the infected body cells, along with the pathogen inside.
What do Perforins do and what are they secreted by
Secreted by T killer cells and punch a hole in the cell surface membrane of infected cells, allowing toxins to enter
Where do B - Lymphocytes remain while they mature
In bone marrow
Where do B - Lymphocytes go once they have matured
They spread through the body, concentrating in lymph nodes and the spleen
What do B -Lymphocytes do
Mature the genes coding for antibodies and are changed to code for different antibodies
What can B Lymphocyte cells do once mature
Each type of B lymphocyte cell can make one type of antibody molecule. At this stage, the antibody molecules do not leave the B-Lymphocyte cell but remain in the cell surface membrane.
What does part of each antibody molecule form
A glycoprotein receptor
What will happen between antigens and B - Lymphocytes if an antigen enters the body
B - Lymphocyte cells with the correct cell surface receptors will recognise and bind to it (clonal selection)
How do B -Lymphocytes divide
Clonal expansion
What two main types of cell do B -Lymphocytes differentiate into
Plasma cells and Memory cells
what happens when an antigen enters the body for the first time
The small number of B-Lymphocytes with receptors complementary to that antigen are stimulated to divide by clonal expansion
What do some of the B-Lymphocytes become after being screed in the primary response and what do they do
Plasma cells that secrete lots of antibodies into the blood, lymph or linings of the lungs and the gut
How long do the plasma cells last in the primary response
Their numbers drop off after several weeks, but the antibodies they have secreted stay in the blood for longer
What do other B -Lymphocytes become if they dont become plasma cells in the primary response
Memory cells
is the primary response quick
No, it is a relatively slow response
