U3 KA6 - Specific Cellular Defences Flashcards
What are Lymphocytes?
White blood cells involved in the specific immune response
What are the two types of Lymphocytes?
B Lymphocytes and T Lymphocytes
What is the role of B Lymphocytes?
To produce specific antibodies against antigens, which leads to the destruction of the pathogen.
Each B-lymphocyte clone produces a specific antibody molecule that will recognise a specific antigen surface molecule of a pathogen.
What are Antibodies?
Y-shaped protein molecules which have binding sites specific to particular antigens. When antibodies bind to antigens, the pathogen is inactivated.
What is an Antigen?
Antigens are molecules, also often proteins, located on the surface of foreign cells (e.g. pathogens) that trigger the specific immune response.
Antigens are specific to each invading pathogen therefore lymphocytes will produce a specific antibody to combat the invasion
What is Clonal Selection Theory?
Once the lymphocyte has been selected for a specific antigen, it multiplies, creating large numbers of identical lymphocytes (clones) bearing that particular receptor.
What does the binding of an antibody to an antigen do?
It creates an antibody-antigen complex.
The formation of this complex inactivates the pathogen (or its toxin), making it more susceptible to phagocytosis.
The antigen-antibody complex can then be destroyed by phagocytosis
Sometimes, the antibody-antigen complex stimulates the activation of proteins that bring about lysis (bursting) of the pathogen.
Describe Allergies in terms of the immune system
B lymphocytes can trigger an immune response against substances that are harmless to the body, for example, pollen, a normally harmless antigen.
An allergy is a normally harmless hypersensitivity by B lymphocytes to an antigen.
What is the role of T lymphocytes?
To destroy body cells that have been infected by the pathogen
What is apoptosis?
Programmed cell death
Describe the process of Apoptosis
- Cell becomes infected with pathogen (virus)
- T Lymphocytes attach onto antigen of infected cells and release proteins.
- These proteins diffuse into infected cells causing production of self-destructive enzymes – it is these enzymes which cause cell death (apoptosis).
- The remains of the cells are then removed by phagocytosis
What happens If the immune system fails to recognise the difference between self and non-self-antigens?
It can result in T lymphocytes attacking the body’s own cells. This can lead to autoimmune diseases.
Examples of autoimmune diseases
- type 1 diabetes
- rheumatoid arthritis
- multiple sclerosis
Whats the difference between the primary immune response and the secondary immune response?
The Secondary immune response is much more rapid because:
- Antibody production is much more rapid
- Concentration of antibodies produced reaches a much higher level (greater)
-The higher concentration of antibodies is maintained for a longer time
What makes the secondary immune response possible?
memory cells
What are memory cells?
These are B and T lymphocytes specific to the antigen which are made in response to clonal selection following first exposure.
When a person is exposed to the same pathogen for a second time, these cells multiply rapidly to produce clones of that lymphocyte to attack and destroy the pathogen before the individual exhibits symptoms.
What is HIV
Human Immunodeficiency Virus (HIV) is a virus that attacks and destroys the body’s T lymphocytes.
What impact does HIV have on the immune system?
The reduction in the number of T lymphocytes in the body due to HIV can then lead to the development of Acquired Immune Deficiency Syndrome (AIDS).
What is AIDS
Acquired Immune Deficiency Syndrome (AIDS).
Individuals with AIDS have a weakened immune system and so are more vulnerable to attack from other infections.
Without immunity, infection by microorganisms, such as those that cause tuberculosis and pneumonia, becomes more common, and can be fatal.
What is the Treatment for HIV/AIDS
These is no cure for HIV/AIDS therefore they are given antiretroviral drugs.
Antiretroviral drugs work by stopping the virus replicating in the body. This allows the immune system to repair itself and prevents the development of AIDS. This treatment is highly effective and allows people infected with HIV to live long and otherwise healthy life.
