Defense Mechanisms Flashcards
Immune system
What are the two types of defense mechanism?
Non-specific
Specific
What are the characteristics of a non-specific response?
(2 points)
The response is:
- Immediate
- Same for all pathogens
What are examples of non-specific responses?
(2 points)
- Physical barriers
- Phagocytosis
What are the characteristics of a specific response?
(2 points)
The response is:
- Slower
- Specific to each pathogen
What are the two types of lymphocyte?
T and B lymphocytes
Which response does the T lymphocyte do?
Cell-mediated response
Which response does the B lymphocyte do?
Humoral response
How does the immune system recognise self and non-self cells?
By analysing the proteins on the surface of the cell
What is the first step of phagocytosis?
Phagocyte is attracted to the pathogen by chemical products
What happens after the phagocyte is attracted to the pathogen by chemical products in phagocytosis?
The phagocyte attaches to the pathogen by its receptors
What happens after the phagocyte attaches to the pathogen by its receptors in phagocytosis?
The phagocyte engulfs the pathogen, forming a phagosome
What happens after the phagocyte becomes a phagosome in phagocytosis?
Lysosomes move towards the phagosome
What happens after the lysosomes move towards the phagosome in phagocytosis?
The lysosomes release lysozymes, which hydrolyse the pathogen
What is an antigen?
Any part of an organism that is recognised as non-self by the immune system and stimulates an immune response
Where are antigens usually found?
Usually proteins on the cell surface membranes or cell walls of invading cells
Where are lymphocytes produced?
In the bone marrow
Where do B lymphocytes mature?
In bone marrow
Where do T lymphocytes mature?
In the Thymus gland
What is the first step of the cell-mediated response?
Pathogen invades body cells or are taken in by phagocytes
What happens after the pathogen is taken in by a phagocyte in the cell mediated response?
The phagocyte places the pathogen’s antigens on its cell surface membrane
What happens after the phagocyte places the pathogen’s antigens on its cell surface membrane in the cell mediated response?
Receptors on specific T cells fit exactly onto these antigens
What happens after receptors on the T cells fit onto the pathogen’s antigens on the phagocyte’s cell surface membrane in the cell mediated response?
The T cell becomes activated and divides rapidly by mitosis
What can the cloned T cells do after the cell-mediated response has taken place?
(4 points
- Develop into memory cells that can respond rapidly if the same pathogen invades again
- Stimulate phagocytes to engulf pathogens
- Stimulate B cells to divide and secrete antibodies
- Activate cytotoxic T cells
How do cytotoxic T cells kill infected cells?
They release a protein called perforin that makes holes in the cell-surface membrane, causing it to become freely permeable to all substances, making the cell die
What does humoral immunity involve?
Antibodies
What is the first step of humoral immunity?
Surface antigens of a pathogen are taken up by a B cell
What is the step after surface antigens of a pathogen are taken up by a B cell in the humoral response?
The B cell processes the antigens and presents them on its surface
What is the step after the B cell processes the antigens and presents them on its surface in the humoral response?
A helper T cell attaches to the processed antigens on the B cell, activating it
What is the step after a helper T cell activates the B cell in the humoral response?
The B cell divides by mitosis to make plasma cells and memory cells
What do plasma cells do?
They secrete antibodies into the blood plasma
What do memory cells do?
When they come into contact with an antigen a second time, they divide rapidly into plasma cells and more memory cells
What is a monoclonal antibody?
When a single antibody can be isolated and cloned outside the body
How can direct monoclonal antibody therapy be used to treat cancer?
- Monoclonal antibodies are produced that are specific to the antigens on the cancer cells
- These antibodies are given to the patient and attach to the receptors of the cancer cells
- They then block the chemical signals that the cancer cells release in order to replicate rapidly
How can indirect monoclonal antibody therapy be used to treat cancer?
Attaching a radioactive or cytotoxic drug to the monoclonal antibody. When the antibody attaches to the cancer cells and kills them
How do pregnancy tests use monoclonal antibodies?
Placenta produces a hormone called hCG, that is found in the urine. hCG in the urine bind to the monoclonal antibodies on the test strip. The hCG-antibody-colour complex moves along the strip until it is trapped by another antibody creating a line
What are ethical issues with the use of monoclonal antibodies?
- Use of mice in production
- Parents need to have full knowledge and give full consent as the use of monoclonal antibodies can have risks as well as benefits
- Safety testing of new drugs can have dangers
What is passive immunity?
The introduction of antibodies into individuals from an outside source.
How quickly is immunity acquired from passive immunity?
Immediately
What are examples of passive immunity?
- Anti-venom given to snake bite victims
- Antibodies passing through the placenta from mother to fetus
What is active immunity?
Stimulation of the production of antibodies by the individuals’ own immune system
How long does active immunity take to develop
Several weeks
What are the two types of active immunity?
- Natural active immunity
- Artificial active immunity
What is natural active immunity?
Results from when the individual is infected naturally. The body creates its own antibodies and continues to do so for many years
What is artificial active immunity?
From vaccination. Inducing an immune response without suffering the symptoms of the disease
What is the intention of vaccination?
To stimulate an immune response against a particular disease. This makes memory cells be produced which allow for a quicker response to a future infection from the same disease
What are the features of a successful vaccination program?
- The vaccine must be economically available to immunise the vulnerable population
- Must be few side-effects
- Means of producing, storing and transporting the vaccine
- Qualified staff to administer the vaccine
- Must be possible to vaccinate the majority of the vulnerable population (herd immunity)
What is herd immunity?
When a sufficiently large proportion of the population has been vaccinated. This makes it difficult for the vaccine to spread
Why is herd immunity important?
Its never possible to vaccinate everyone in a large population. Therefore if most of the population is vaccinated, the transmission of the pathogen is interrupted.
How might a vaccine not induce immunity?
- If an individual has a faulty immune system
- Individuals could develop the disease immediately before they are immune, and harbour the disease and transmit it
- The pathogen could mutate and therefore develop different antigens
