Immunology Flashcards
State 2 ways that pathogens can cause harm/disease (2)
Produce toxins which can directly damage tissues
Can sometimes replicate inside and destroy host cells
What is an antigen? (1)
A foreign protein that stimulates an immune response that results in the production of a specific antibody
What is a phagocyte? (1)
White blood cell that engulf and destroy any cell that presents a non-self-antigen
Describe the process of phagocytosis (4)
Pathogen engulfed by phagocyte (endocytosis) into the cytoplasm and in a vesicle which is called a phagosome
Lysosomes fuse with phagosome releasing hydrolytic enzymes which hydrolyses the pathogen
Waste materials released from the cell by exocytosis
Antigens presented on the cell surface membrane and the phagocyte becomes an antigen presenting cell
Give 2 differences between specific and non-specific immune responses
Name the two types of specific immunity (4)
Non-specific: (phagocytosis) same for all pathogens
Specific: (B and T lymphocytes)
Non-specific: immediate
Specific: time lag
Cell mediated and humoral response
Outline the process of the cell mediated response (4)
T helper cell with specific receptors binds to complementary antigen on APC
Cytokines released which:
Stimulate clonal expansion of complementary T helper cells - become memory cells or trigger humoral response
Stimulates clonal expansion of cytotoxic T cells- secrete enzyme perforin to destroy infected cells
Role of Cytotoxic killer T cells (2)
Locate and destroy infected body cells that present the correct antigen
Bind to APC (antigen-presenting-cells)
Outline the process of the humoral response (4)
Specific T helper cell with specific receptor binds to complementary antigen and activates a specifically complementary B cell
Cytokines (released by specific T helper cell) signal the specific B cell to clone by mitosis
B cells differentiate into plasma cells and memory (B) cells
Plasma cells secrete antibodies
What is the role of memory (B) cells? (1)
Remain in the body to respond to pathogen rapidly and extensively if there is a future re-infection
Contrast the primary and secondary immune response (9)
Primary:
Initial response when a pathogen is encountered
Small number of antibodies
Slower rate of antibody production
Secondary:
Re-exposure to same antigen
Faster rate of antibody production
Higher concentration of antibodies
Antibodies level remain higher after the secondary response
Shorter time lag between exposure and antibody production
Pathogen usually destroyed before any symptoms
What causes antigen variability? (4)
Random genetic mutation changes DNA base sequence
Results in different sequence of codons on mRNA
Different primary structure of antigen = H-bonds, ionic bonds and disulphide bridges form in different places in tertiary structure
Different shape of antigen
Explain how antigen variability affects the incidence of disease? (2)
Memory cells no longer complementary to antigen - individual no immune - can catch the disease more than once
Many varieties of a pathogen - difficult to develop vaccines containing all antigen types
What is an antibody? (2)
A protein made in response to a foreign antigen which has a binding site which binds specifically to an antigen.
Produced by specific plasma cells
Describe the structure of an antibody (4)
Quaternary structure - 4 polypeptide chains
2 light chains bonded to 2 longer heavy chains
Constant region: main part of antibody which is the same in all antibodies
Variable region: different primary structure so different tertiary structure
Disulphide bridge - joins two different polypeptides
How do antibodies destroy pathogens? (5)
Agglutination: specific antibodies bind to the antigen on pathogen and clump them together so that phagocytes can ingest them more easily
Opsonisation: marking pathogens so phagocytes recognise and destroy the pathogen more efficiently
Lysis: bind to antigens and lead to destruction of the pathogens membrane
Anti-toxin and anti-venom: bind to toxins or venom to prevent these molecules from binding to complementary target receptors
Prevent pathogen replication
What is passive immunity? (3)
The short-term immunity that results from the introduction of antibodies from external sources
No production of memory cells
No exposure to antigen
What is active immunity? (3)
Antibodies produced in response to exposure to an antigen.
Provided by the memory cells that are produced after a primary immune response to a pathogen
Exposure to antigen
Why are antibodies ineffective against viruses? (2)
Antibodies often work by damaging murein cell walls to cause osmotic lysis - viruses have no cell walls
Viruses replicate inside host cells - difficult to destroy them without damaging host cells
How do vaccinations work? (7)
Vaccine contains antigen from pathogen
Macrophage presents antigen on its surface
T cell with complementary receptor protein binds to antigen
T cell stimulates B cell
(With) complementary antibody on its surface
B cell secretes large amounts of antibody;
B cell divides to form clone all secreting / producing same antibody.
What kind of pathogens are vaccines ineffective against? (1)
Pathogens that show antigenic variability
Why are booster vaccines sometimes administered? (2)
To make sure that memory cells are still present in the blood which increases efficiency of the vaccine
When the vaccine does not induce a strong response these can be given to maintain immunity
How do vaccines provide herd immunity? (2)
When significant proportion of population is vaccinated, the pathogen is less likely to affect a non-immunised individual
Reduces available carriers of the pathogen
What are the ethical issues with vaccinations? (4)
Development and testing involve use of animals - which can infringe rights of animals
Can cause potentially dangerous side effects
Vaccine is only available to those who can afford it (people in poor countries cannot)
Human testing - putting people at risk and it is mostly the poor people who choose to take part in trials
What are monoclonal antibodies? (1)
Antibodies with the same tertiary structure made from identical/cloned B cells
