Immune System Flashcards
To understand the different kinds of immune responses and how they occur
What is a phagocyte?
A phagocyte is a type of white blood cell that carries out phagocytosis.
What are the stages of phagocytosis?
A phagocyte recognises the foreign antigen on a pathogen
The cytoplasm of the phagocyte moves around the pathogen, engulfing it.
The pathogen is now contained in a phagocytic vacuole in the cytoplasm of the phagocyte.
A lysosome fuses with the phagocytic vacuole. The lysozymes break down the pathogen
The phagocyte then [resents the pathogen’s antigens- it sticks to the antigens on its surface to activate other immune system cells.
What is a lysosome?
A lysosome is an organelle that contains enzymes called lysozymes.
What are T-cells and what do they do?
A T cell is another type of white blood cell. It has receptor proteins on its surface that bind to complimentary antigens presented to it by a phagocyte.
What do helper T cells do?
Helper T cells release chemical signals that activate and stimulate phagocytes.
What do cytotoxic T cells do?
They kill abnormal and foreign cells.
What are B cells and what do they do?
B cells are also a type of white blood cell
They’re covered with antibodies . Each B cell has a different shaped antibody in its membrane and so different ones bind to different shaped antigens.
What are antibodies?
Antibodies are proteins that bind antigens to form an antigen-antibody complex
What happens when a surface of a B cell meets a complimentary shaped antigen?
It binds to it
This activates the B cell. This is clonal selection.
The activated B cell divides into plasma cells.
What do plasma cells do?
Plasma cells make more antibodies to a specific antigen
They secrete loads of antibodies specific to the antigen. These are called monoclonal antibodies.
What is the structure of an antibody like and how does this help in the immune response?
An antibody has 2 binding sites so can bind to 2 pathogens at the same time. This means that pathogens become clumped together. This is called agglutination.
Antibodies are proteins- made up of chains of amino acids. The specificity of an antibody depends on its variable region, which form the antigen binding site. Each antibody has a variable region with a unique tertiary structure that’s complimentary to one specific antigen.
All antibodies have the same constant region
What does a cellular immune response involve?
T cells and other immune system cells
What does a humoral immune response involve?
B cells, clonal selection, and the production of monoclonal antibodies.
What is the primary immune response?
When an antigen enters the body for the first time
The immune response is very slow as there aren’t many B cells around yet to produce the antibodies for this specific antigen.
Eventually the body will produce enough of the right antibody to overcome the infection
Both T and B cells produce memory cells after being exposed to an antigen.
What do memory T cells do?
They remember the specific antigen and will recognise it a second time round
