Disease And Immunity Flashcards
(32 cards)
What is a pathogen?
A pathogen is a microorganism that causes disease.
Name three types of pathogens
Bacteria, Fungus, viruses
State two ways in which pathogens can cause disease
By releasing toxins
Damaginh host cells
What is the difference between specific and non specifoc responses to disease?
Specific is much slower (yet quicker after re-infection)
Specific is only affective against a specific pathogen, non- specific works on a range of pathogens, and always uses the same response
Non-specific is present from birth, specific isnt
What is an antigen?
A foreign protein that stimulates an immune response and the production of antibodies.
How can a cell identify a virus?
Via their specifoc antigens on the surface of the virus, that are specific to each molecule
Name a non specifoc immune response
Phagocytosis
Describe the stages of phagocytosis
A phagocyte regocnises and binds to the specific antigen on the pathogen.
It engulfs the pathogen, enclosing it in a vesicle.
Lysosomes fuse with the vesicle, and its hydrolytoc enzymes damage the bacteria cell walls
The enzymes digest the pathogen by hydrolysis of its molecules
The phagocyte places the pathogens antigens on its surface membrane, becoming an antigen presenting cell.
How can a cell become an antigen presenting cells?
Cells that:
Are infected by a virus
An abnormal cell that has become cancerous
A phagocyte that has just engulfed and hydrolysed a pathogen
What is the difference between cellular and humoral specific immune responses?
Humoral is mediated by B cells, cellular is mediated by specific T- helper cells
Humoral produces and releases antibodies, cellular destroys infected cells
Describe the process of the cellular immune response
A specific t-helper cell binds to an antigen on the antigen presenting cell, via its complimentary receptors
This stimulates the specific T-helper cell to divide by mitosis, to produce more T-helper cells and memory cells
The T-helper cells release cytokines, which stimulate specific cytotoxic T- cells to divode by mitosis
The cytotoxic cells release perforin, which destroys the infected cell by osmotoc lysis.
Describe the process of the humoral immune response
The specofc B cell binds to an antigen on the pathogen, via its complimentary receptors
Cytokines released by specifoc Thelper cells activate the B cells, causing them divide by mitosis to prodice cells that differentiate into plasma cells and memory cells.
Plasma cells produce and release antibodies
Memory cells remain in the body, and upon second exposure prodice plasma cells that release more antibodies more rapidly
How many antibodies can plasma cells produce per second?
Around 200
What are antibodies?
Proteins synthesised by specifoc plasma B cells.
They have a specific tertuary structure, that is complimentary to a particular antigen
What is the role of antibodies?
Antibodies can bind to specific antigens (due to their complimentary tertiary structure) to form an antigen- antibody complex.
They then neutralise the pathogens, by clumping them together, allowing phagocytes to engulf more pathogens. This is called agglutination
What are monoclonal antobodies?
Antibodies that are produced by the same specific B-cell/ plasma cells. They have the same tertiary structure and will bond to the same antigen
What are five uses of monoclonal antibodies?
Medical diagnosis
Pregnancy testing
Targeted drug treatments
Drug testing
Covid testing
Explain the process of the Elisa test is
A container is coated in monoclonal antibodies, specific to the antigen being tested for
The sample being tested is added to the container. If the antigen is present it will bind to the monoclonal antibodies.
The container is washed to remove any unbound antigens
A second monoclonal antibody with an emzyme attached is added, and will bind to another site of the antigens
The container is washed again
The substrate to the enzyme is added, and hydrolysed (if the antigen and therefore enzyme is present). This will cause a colour change, indicating a positive result
What is passive immunity?
Where antibodies are aquired from an outside source. It give immediate immunity yet the effect is short lived
What is active immunity?
Immunity stimulated by the production of antibodies
It is not immediate as memory cells need to be made, yet this means the effect is long lasting.
It can be aquired naturally (by pathogens) lr artificially (vaccinations)
What are vaccinations?
The introduction of an antigen into an organism, with the intention of making them immune to a specifoc disease
Explain how vaccinations provide immunity for a disease
A vaccination contains a specific inactive/ weakened antigen
The antigen will be displayed on an antigen presenting cell.
Specific Th cells will bind to the antigen, and release cytokines
Cytokines will activate specific B cells to divide by mitosis, producing memory cells and plasma cells
Upon second exposure to the same antigen, memory celld will prodice olasma cells, whoch will produce and release more antibodies more rapidly
The pathogen is therefpre destroyed before symptoms start
What makes a vaccination programme successful?
The vaccine must have very few side effects
Must have means of administration
Easily stored and transported
Economically available in larger quantities
What is heard immunity?
Where around 90% of the population are vaccinated against a particular disease, which prevents the spread of the disease to people who are not vaccinated/ immune
