Topic 2 - Immunity Flashcards
What is a pathogen
A disease causing microorganism
How does an infection occur
If the pathogen gets into the host and colonises its tissues
How does a disease occur
When an infection leads to recognisable symptoms in the host
What is an epidemic
An outbreak of an infectious disease that spreads rapidly among individuals of a population at the same time
What is a pandemic
An outbreak of a disease that occurs over a wide geographic area and affects an exponentially high proportion of the population
What are the three lines of defence in the body to resist pathogens
To prevent entry
If this fails, phagocytes are sent to gather at the site of infection to ingest the pathogen
If this fails, the body targets that particular pathogen, in a specific immune response
What are the barriers of pathogen entry
The skin, consists of layers of dead cells filled with a tough protein (keratin) and oily secretion
Tears and saliva that contain lysozyme
Mucus which traps microorganisms and contains lysozyme
Acid in the stomach
How do pathogens enter the body
Through broken skins or via the lungs and intestines
What are 2 types of phagocytes at accumulate at the site of infection
Polymorphs and macrophages
What is the immune response, and what white blood cell does it involve
A specific response to the detection of pathogens in the body, involving lymphocytes
What is an antigen
A foreign or ‘non-self’ molecule that is carried on the cell-surface membrane of pathogens
What is a special protein receptor
A receptor carried on the cell-surface membrane of a lymphocyte, which is complementary in shape to a specific antigen
What are stem cells
Unspecialised cells that can give rise to a variety of specialised cells
Why is there no response to ‘self’ antigens
There are no lymphocytes set up to respond to the molecules of the individuals cells
What are the two specific types of Lymphocytes
B-Cells and T-Cells
What is the difference in where B and T cells mature
B-Cells continue maturing in the Bone Marrow
T-Cells mature in the Thymus
What immune response are B-Lymphocytes involved in
Antibody-mediated immunity
What type of immune response are T-Lymphocytes involved in
Cell-mediated immunity
What is the nature of the immune response in B-Lymphocytes
They secrete antibodies which counter the antigen-carrying pathogens
What is the nature of the immune response in T-Lymphocytes
They attack infected cells with antigen present on the membrane
How does a Lymphocyte become activated/ sensitised, and what do they do once they become sensitised
It comes into contact with a ‘non-self’ antigen, they divide by mitosis to clone and differentiate into a variety of cells
What are antibodies
Secreted material from the Cloned B-Cells involved in antibody-mediated immunity
What are immunoglobulins
Globular protein antibodies
What part of the antibody is specific to a particular antigen
The binding site
What are some ways in which antibodies can function
They may neutralise toxins produced by bacteria - antitoxins
Clump or agglutinate bacteria - agglutinins
Attaching to viruses to prevent entry to host cells
Destroy bacterial cell walls, causing lysis
Attach to bacteria, so phagocytic cells can identify them
What are the four steps in antibody mediated immunity
- Bacteria enters the body
- Bacterial antigen is recognised by the correct B-Cell with the complementary receptor
- The sensitised B-Cell divides by mitosis to produce plasma cells and memory cells
- Plasma cells produce antibodies, which destroy the bacteria
What are the 4 different types of cloned T-Cells
Killer T-Cells
Helper T-Cells
Memory T-Cells
Suppressor T-Cells
How do Killer T-Cells work
They destroy infected cells directly by attaching to the antigens on the surface of the target cell and realising preforin, which produces pores within the cell-surface membrane, resulting in lysis of the cells
How do Helper T-Cells,work
They secrete cytokines which promote the activity of other cells, I.e they stimulate B-Cells to produce plasma cells, and they activate Killer T-Cells
How do Memory T-Cells work
They stay in the body, so that if the antigen appears again, it results in rapid destruction of the cells with the antigen present
How do Suppressor T-Cells work
They release their own cytokines after the successful elimination of the pathogen, which signals the deactivation of T-Cells and B-Cells
What are the 4 steps of Cell-Mediated Immunith
- The host cell becomes infected with viruses with viral antigens present
- The viral antigen is recognised by the correct T-Cell with the complementary receptor
- The sensitised T-Cell divides by mitosis to produce different types of T-Cell
- The Killer T-Cells recognise infected cells and destroy them before viruses reproduce
How to B-Cells and T-Cells complement eachother
Plasma B-Cells destroy ‘free’ pathogens, and Killer T-Cells destroy the infected cells
What are some other cells that Killer T-Cells destroy
Cancer cells
Cells of Transplanted Tissue
What are the two types of immunity
Passive and active
What is passive immunity
Occurs when an individual receives antibodies from another source
What are the two types of passive immunity
Natural and artificial
How does natural passive immunity occur
When antibodies pass naturally from mother to baby across the placenta and in the mothers breast milk
When does artificial passive immunity occur
When antibodies are administered by injection. They can be obtained from a person recovering from injection, from an animal, or as monoclonal antibodies produced by genetically modified mouse cells
Why is passive immunity temporary
The antibodies are used up in antigen-antibody reactions and the recipient has no plasma cells to make more
What is serum
Blood plasma without clotting factors, but contains antibodies
What is active immunity
Occurs when an antigen enters the body and stimulates the body’s immune system to produce antibodies and memory cells
What are the two types of active immunity
Natural and artificial
When does natural active immunity occur
When a person is infected
What is the difference in the primary and secondary response
The secondary response has an immediate start
The secondary response has faster production of antibodies, and a higher maximum concentration
The secondary response lasts a longer time
Why is the secondary response faster than the primary response
Memory cells produced in the primary response, destroys the antigens if they show again in the secondary response
What is artificial active immunity
It involves vaccination
What is vaccination
It involves injecting a person with antigenic material that has been rendered harmless but leaves the surface antigens intact
What is a booster vaccination
A secondary injection of a vaccine, which further heightens the immune system
What is herd immunity
Occurs when a large percentage of a population has become immune to an infection, so providing a measure of protection for individuals who are not
What is a monoclonal antibody
An antibody produced from a single clone of plasma cells. Thus, they are identical and are complementary to a single, specific antigen
What is an immunoassay
A test to measure the presence of a molecule through the use of an antibody
What is a bio marker
A naturally occurring molecule, often a protein, which can be detected and acts as an indicator of a disease or the effects of its treatment
What do successful organ transplants rely on
Tissue typing
Use of X-Rays
Immunosuppression
What is tissue typing
Where the compatibility of the donor and the recipient cell-surface membrane are similar and then donor tissue is used for which there is an optimal match
Why are X-Rays used in organ transplants
To irradiate bone marrow and lymph tissues, so as to inhibit the production of lymphocytes and therefore slow down rejection
Why is immunosuppression used in organ transplants
To inhibit DNA replication, cell division and the cloning of lymphocytes, and so delay the rejection of the graft
What is the ABO blood system
The blood-type system determining the presence of anti-A and anti-B antibodies in people who lack corresponding antigens from birth
What antigens are present in the blood groups A, B, AB and O
A - A
B - B
AB - A and B
O - none
What antibodies are present in the blood groups A, B, AB and O
A - anti-B
B - anti-A
AB - none
O - both anti-A and anti-B
What are agglutinins
If they encounter red blood cells with the complementary antigen, they will cause them to stick together or agglutinate
What occurs in an unsuccessful blood transfusion
Donated blood with agglutinate in the recipients blood system, which clumps blood and would block capillary networks, which cause organ failure and death
What blood group can receive A blood
A - Yes
B - No
AB - Yes
O - No
What blood group can receive B blood
A - No
B - Yes
AB - Yes
O - No
What blood groups can receive AB blood
A - No
B - No
AB - Yes
O - No
What blood groups can receive O blood
A - Yes
B - Yes
AB - Yes
O - Yes
What blood group is the universal donor, and why
Blood group O, as it lacks both A and B antigens and is safe to use in all transfusions
What blood group is the universal recipient and why
Blood group AB, as it lacks both anti-A and anti-B antibodies, so can safely receive blood of any blood type
What is the Rhesus system
Depends on whether a marker protein is present
What is the difference between Rh -ve and Rh +ve
The rhesus antigen. If a person possesses it, they are Rh +ve, and if they don’t they are Rh -ve
What antibodies do Rh -ve people produce
Anti-D antibodies
How is an Rh -ve mother giving birth to two Rh +ve babies dangerous
Once a Rh -ve mother has given birth to a Rh +ve baby, the mother produces anti-D antigens. Any subsequent Rh +ve baby may receive anti-D from the mother will result in agglutination of the baby’s blood
What is an antibiotic
Substances produced by microorganisms that act against bacteria
What is antibiotic resistance
When an antibiotic becomes less effective due to the continuous use of it
How can you reduce the risk of antibiotic resistance
Antibiotics are only used when necessary
A person prescribed antibiotics completes the course
Hospitals take care to no spread bacteria between patients
Consideration to using more than one antibiotic to treat a disease
Some antibiotics are seldom used and kept as a ‘last resort’
What is sepsis
The presence in tissues of harmful bacteria and their toxins, through infection of a wound
