Week 3 - Adaptive Immunity Flashcards
Define Immunity
Capacity of the immune system to successfully defend the body against a potentially infectious agent
What cells are involved in adaptive immunity?
Lymphocytes
What are the 2 types of lymphocytes?
- B cells
- T cells
Where do both types of Lymphocytes originate from?
Stem cells in bone marrow
What is an Antigen?
Any substance that the body recognises as foreign, or non-self
Name the two categories of adaptive immunity
- Anti-body mediated immunity
- Cell-meditated immunity
Describe ‘Anti-body meditated immunity’
- This response activates B-cells that then proliferate and produce:
- Plasma cells
- Memory cells - Involves the activation of B cells and secretion of antibodies when in contact with a pathogen.
- Produces antibodies to destroy microbes
Describe ‘Cell-meditated immunity’
- Destroys infected cells
- Immune response that does not involve antibodies.
What cells are involved in ‘anti-body meditated immunity’?
- B cells
- Plasma
- Memory
What cells are involved in ‘cell-meditated immunity’?
- T cells
- Memory-T cells
How do B cells provide immunity?
Fight bacteria and viruses by making Y-shaped proteins called antibodies, which are specific to each pathogen and are able to lock onto the surface of an invading cell and mark it for destruction by other immune cells
How do Plasma cells provide immunity?
Produce antibodies which circulate in the blood and other body fluids which target bacteria and their toxins and prepare them for destruction, also target viruses before they enter body cells
How do Memory cells provide immunity?
Persist in the body for months - years and can react with the same antigen again if it enters the body at a later date
How do T cells provide immunity?
Destroy cells that harbour viruses or bacteria and cancer cells and parasites. They fight intracellular pathogens
How do Memory T cells provide immunity?
Specifically produced to the microbe
Where does ‘anti-body meditated immunity’ occur?
In the bone marrow
Where does ‘cell-meditated immunity’ occur?
In infected cells
What is the primary immune response?
Response of the immune system the first time it is exposed to a particular antigen. There is a lag period 5 – 7 days in which there’s no increase in the level of antibodies in the blood.
What is the secondary immune response?
Due to increased numbers of specific memory cells which are more easily stimulated to produce plasma cells which produce antibodies. The memory cells provide immunological memory.
Why is the secondary immune response important?
Causes the many memory cells to rapidly produce new plasma cells & large numbers of antibodies within a few days. Possessing memory cells & the capacity to produce a rapid secondary response means that a person is immune to that specific antigen.
What are the 4 classes on antibodies?
- igG
- igA
- igM
- igE
What are some features of igG class?
- Protect against bacteria, neutralise toxins and viruses, trigger complement, make phagocytosis more effective.
- The longest-lasting of the antibodies in the blood
- Can cross the placenta so foetus and new-born get some protection from mother.
What are some features of igA class?
- Most common antibody in secretions and on mucus membranes
- Bind antigens before they invade tissues and prevent microbes adhering to mucus membranes - especially in respiratory system
- Most abundant antibody in the body
Name some examples of mucus membranes
- Breast milk
- Saliva
- Tears
What are some features of igM class?
- First type to be produced when antigen is encountered
- Lasts only a short time therefore presence of these indicates a very recent or current exposure to the antigen
- Very good at clumping antigen, and triggering complement
What are some features of igE class?
- Tiny amounts only
- Involved in allergic reactions
- Bind to mast cells and basophils which release histamine when antigen binds to igE
Name and describe the 4 functions of antibodies
- Enhance phagocytosis. Antibodies coat the microbe making it easier for the phagocyte to recognise & ingest the microbe.
- Activates complement. When the antibody connects to the antigen it changes shape exposing a section of the antibody where complement proteins can bind. Complement is activated.
- Neutralisation: Antibodies bind to & block the attachment sites on the microbe to stop it binding to the host cell.
- Agglutination into large complexes so reduces the number of infectious units phagocytes have to deal with.
Describe the role of major histocompatibility complex (MHC)
To prevent the immune system from attacking our own cells. We have proteins on the surface of our cells which identify us as self
How do T cells destroy infected cells?
A cell infected by a virus or bacterium displays microbial antigen fragments on its surface. The cytotoxic T cell binds to the infected cell and inserts perforin proteins into the cell membrane, which injects enzymes which kill the cell. This stops the virus multiplying and exposes it to antibodies outside the cell. Memory T cells specific to the microbe are produced
What are antibodies also known as?
Immunoglobulins
