Immunology Flashcards
State 2 ways in which pathogens can cause harm/ disease
-can produce toxins that directly damage the tissue
-can sometimes replicate inside then destroy host cells
Define the term ‘antigen’ (2)
- a molecule (usually a protein) that stimulates an immune response that results in the production of a specific antibody (ANTibody GENerator)
What can specific molecules on the plasma cell surface membrane identify?
-pathogens
-cells from other organisms of the same species
-abnormal body cells
-toxins
How can pathogenic bacteria help humans?
-pathogenic bacteria have different proteins in their cell membranes to our proteins
-our immune system can detect these different antigens and make antibodies against them (with complimentary shapes)
What is the surface of all cells/ pathogens covered in?
-specifically shaped antigens that help identify each particular type of cell to the host organism
What happens if antigens are not recognised?
-the body will treat that cell/ pathogens as non self and initiate an immune response which will lead to the destruction of the cell/ pathogens/ protein
-glycolipids and glycoproteins are examples of antigens
What are self antigens?
When your immune system doesn’t react against your on cell membrane proteins
What are non self antigens
- the proteins on the surface of pathogens or transplanted cells are non self and your immune system does react against them
What is a non specific immune response?
-first line of defence
-skin, mucous secretion, blood clotting, phagocytic cells (macrophages), tears (lysosomes)
What s a specific immune response?
-specific to a certain antigen
-T Cells (cell mediated response)
-B cells (humoural response = production of antibodies)
What type of immunity is phagocytosis ?
Non specific
What are phagocytes?
- a group of white blood cells which can distinguish between cells and dont display self antigens
-they will engulf and destroy non self antigens through phagocytosis
-can detect chemical signals produced by pathogens
What does a macrophage do?
Present a small fragment of the original pathogen on its surface
describe the process of phagocytosis (7)
1+2- pathogen is engulfed by phagocyte
3- engulfed pathogen enters the cytoplasm of the phagocyte in a vesicle (now called a phagosome)
4- lysosomes fuse with phagosome releasing hydrolytic digestive enzymes (lysozomes)
5- lysosome enzymes hydrolyse the pathogen
6+7- waste materials are released from the cell by exocytosis and antigens presented on the cell surface membrane and the phagocyte become an antigen presenting cell
Why might phagocytosis not always be the best option?
-in case of an infection, it takes far too long to destroy all the invading pathogens in the event of an infection, which may result in damage to tissues and organs
Some white blood cells are phagocytic. Describe how these phagocytic white blood cells destroy bacteria (5)
-phagocyte attracted to bacteria by chemicals/ recognise antigens on bacteria as foreign
-engulf/ ingest bacteria
-bacteria in vacuole / vesicle
-lysosome fuses with/ empties enzymes into vacuole
-bacteria digested/ hydrolysed
What are the stages of the cellular response?
- Antigen presenting
- Clonal selection
Describe the antigen presenting stage in cell mediated immunity (primary response)
- specific T helper cells can respond directly to a pathogen or its antigen OR they respond to antigen presenting cells, that presents the specifically complimentary antigen to their receptors
-the antigen presenting cell presents the pathogens antigen on its cell surface membrane
Describe the clonal selection stage in cell mediated immunity (primary response)
- a specific t helper cell binds to presented antigen via its complimentary response
-t helper cell is activated and clones (through mitosis) to produce many t helper cells with complimentary receptors to the antigen
describe cell mediated immunity/ primary response
What are the 3 types of T cells?
t helper cells
t memory cells
Cytotoxic (killer) T cell
Describe the roles of a t helper cell
-specific Th cell binds to antigen presenting cells
-release cytokines that attract phagocytes to the area of infection
-release cytokines that activate cytotoxic killer T cell
-activates a specifically complimentary B cell
-form memory Th cells
describe the roles of a cytotoxic killer T cell
-locates and destroys infected body cells that present to the correct antigen
-binds to antigen presenting cells
-releases perforin which creates holes in the cell surface membrane which destroys the APC
What happens when a specific T helper cell has been activated?
The cloned daughter cells differentiate into 3 types of T cells
What is the humoural response?
-when B cells are activated to produce antibodies
-B cells must be stimulated by their complimentary t helper cell by the release of cytokines
Describe B cell activation
- a specific T helper cell with the correct receptor binds to presented antigen and then locates and activates a specifically complimentary B cells must
-the specific T helper cel releases cytokine chemicals that signal the specific B cell to clone by mitosis (clonal selection)
What two types of cells can B cells differentiate into?
-plasma cells
-memory (B) cells
What do plasma B cells do?
-produce and secrete vast quantities of specific antibodies into the blood plasma
What do memory B cells do?
-remain in the body to respond to the pathogen rapidly and extensively in case of future reinfection (stay in blood circulation)
Describe the primary response for infection
-the whole process from initially recognising a pathogen as non self, up to producing antibodies
Define the term antibody
-a protein made in response to a foreign antigen- has binding sites which bind specifically to an antigen
-a specific antibody is produces by a specific ‘plasma cell’ (B plasma cell)
Describe the structure of an antibody
-a complex protein with a quaternary structure
-made up of 4 polypeptide chains
-the antibody is Y shaped
Draw and label an antibody
What part of the antibody is the main/darker part? (At the bottom of the Y)
Constant region
What part of the antibody is the constant region?
The main/ darker part
Which part of the antibody is the bottom of the Y?
Constant region
Which part of the antibody is the variable region?
-the top/ arms of the Y
-the lighter part of the antibody
What is the variable region of the antibody?
-a region with a different primary structure and therefore a different tertiary structure (different shapes)
What do all antibodies consist of?
-constant region
-variable region
-antigen binding site
-heavy chain 1
-heavy chain 2
-light chain 1
-light chain 2
-disulphide bridges between R groups
-receptor binding sites
What does an antigen binding sites do?
Bind 2 antigens at the same time
How are antigen antibody complexes formed?
-due to their specific binding sites, antibodies only bind to specific antigens forming a (permanent) antigen-antibody complex
How do antibodies assist in the destruction of pathogens?
-agglutination
-opsonisaton
-lysis
-anti toxin & anti venom
-prevent pathogen replication
Describe how agglutination can destroy pathogens?
Specific antibodies bind to the antigens on pathogen and clump them together
Describe how opsonisation can destroy pathogens
Marking pathogens so phagocytes recognise and destroy the pathogen more effectively
describe how lysis can destroy pathogens
Binds to antigens and lead to destruction of the pathogens membrane
How do anti toxins and anti venom destroy pathogens
Binds to toxins or venom (both usually proteins) to prevent these molecules from binding to their complimentary target receptors
What happens to activated B cells?
-once activated B cells clone by mitosis to produce plasma and memory cells as part of the humoural response
-these memory cells are not directly involved in destroying the invading pathogen
-they remain in the circulation in case of future reinfection by the same pathogen
What happens if memory cells encounter the same antigen again?
-if the memory cells encounter the antigen again, they are rapidly activated (by cytokines secreted by T helper cells) and divide rapidly by mitosis
What happens to genetically identical cloned memory cells?
-they differentiate into plasma cells and even more memory B cells
What do plasma cells produce?
-vast numbers of the specific antibody for the invading pathogen in a short period of time
What is the secondary response?
-the activation of memory cells o produce antibodies
Describe the secondary response
-a rapid and extensive response
-the antigen is normally eliminated before it can cause disease or any symptoms develop (makes the person immune to the disease)
-in a secondary response more antibodies are produced more rapidly
Describe the term antigenic variability (in terms of a secondary response)
-a change in antigen from the previous infection due to gene mutations in the pathogen
Why is the secondary immune response effective?
-most pathogens have the same antigens on their surface, and so are recognised by memory cells when reinfection occurs
-some pathogens have antigens that mutate and change shape (flu, HIV)
What happens when a gene is mutated in a pathogen?
-gene mutations in pathogens lead to a change in the tertiary structure of antigens specific to the B cell (change due to previous infection)
-this means memory B cell antibodies will no longer be complimentary to the mutated pathogen so no antigen-antibody complex can form
-meaning the individual can’t initiate a secondary response
What are the types of immunity?
-active and passive
Describe passive immunity (5)
-no exposure to antigen
-antibodies are given (mother, antiserum)
-no memory cells are produced
-short term
-fast acting
(Short lived protection as antibodies are recognised as non self so are destroyed so no memory cells re produced)
describe active immunity (5)
-exposure to antigen
-antibodies are produced
-memory cells produced
-long term
-takes time to develop
(Make your own antibodies so is long lasting as it can make memory cells e.g. natural production after infection or artificial production after vaccination)
contrast active and passive immunity (5)
What do vaccines contain?
-antigens from dead, weakened or attenuated pathogens
How do vaccines work (6)
-pathogen is engulfed by a phagocyte and displayed on an antigen presenting cell
-a specific T helper cell binds to the antigen on the antigen presenting cell
-the specific T helper cel stimulates a specific B cell (by releasing cytokines)
-b cell divides by mitosis to produce plasma and memory cells
-plasma cels produced and release antibodies
-memory cell recognise the antigen on second infection
What may vaccines not be effective against?
Pathogens which show antigenic variability
What can vaccines be? (4 things)
- Antigens isolated as fragments of the pathogen (HPV vaccine)
- Weakened or ‘attenuated’ heat treated versions of the pathogens 9measles- contain ‘live bacterium’ but not pathogenic
- Inactivated toxin from pathogen (tetanus virus)
- Killed pathogen 9whooping cough vaccine)
What is herd immunity?
-if enough individuals in the population are vaccinated (85%), then there is little chance of the disease spreading, therefore even non vaccinated people will be protected
Describe some minor vaccination ethics
-some vaccinations can cause side effects but they are usually mild and cause fewer problems than the disease itself
-in some individuals, side effects may result in complications that could have permanent, severe effects on the individual
-it is the decision of the individual (with medical advice) to decide whether to vaccinate or not
List some ethical issues associated with vaccines and heir development
-development and testing involve the use of animals- does this infringe animals rights?
-human testing (clinical trials)
-is it available to everyone or only those who can afford it?
-balancing risk of side effects against possible benefit
-should vaccination programs be compulsory?
-should we be aiming to eliminate an organism (loss of genetic variability)
What is a monoclonal antibody?
-antibodies with the same tertiary structure
What are some uses of monoclonal antibodies?
-research
-immuno assays (pregnancy test kits and ELISA) (ELISA is used to diagnose HIV)
-diagnosis (shows presence of a certain antigen
-targeting drugs
-killing specific cells
-isolating specific chemicals
What are some ethical issued with monoclonal antibodies?
-similar to vaccines
-involve inducing tumours in mice
-mice may be genetically engineered to produce human antibodies
-1/2 examples of human volunteers suffering major ad unexpected side effects when testing the monoclonal antibody
What is an ELISA test?
-used to determine the presence of the antibody (indirect ELISA) or the antigen (sandwich ELISA)
-used to diagnose HIV
What does indirect ELISA determine/ look for?
-presence of an antibody
What does sandwich ELISA look/ test for?
-presence of an antigen
Draw and label a diagram of indirect ELISA
Draw and label a diagram of sandwich ELISA
Describe the process of HIV testing
- Most common method: stick HIV antigens (capsid protein) to the indside of the wells
-wash off any unbound antibody - Add a blood sample to the wells that may contain anti-HIV antibodies (if infected)
3.A second anti-human antibody is then added that is complimentary to the human antibody
-wash off any unbound antibody (IF YOU DON’T, YOU MAY GET A FALSE POSITIVE) - The anti-human antibody has an enzyme attached to it that can catalyse conversion of a substrate to a coloured product
What may HIV cause?
AIDS
Draw and label an example HIV structure
Describe the process of HIV replication
- Attachment proteins on HIV binds with a protein receptor commonly found on T helper cells
- Capsid fuses with cell surface membrane and releases viral RNA and enzymes into the helper TH cell
- The HIV’s reverse transcriptase converts viral RNA into cDNA using host nucleotides and cDNA converted to dsDNA by DNA polymerase
- Viral cDNA moves into nucleus of the T cell and is inserted into the host cell genome (DNA). The person/ cell is now infected
5 & 6. Transcription of viral DNA into viral mRNA which is translated to produce HIV proteins. The infected T helper cell starts to manufacture new HIV virions/ particles - Particles (virions) break away from the T helper cell with a selection of host cell surface membrane which forms their lipid envelope, with T helper receptor proteins embedded (to gain access into more t helper cells)
-over time, this leads to a reduction in the number of t helper cells or reduction by inactivation of T helper cells
How do antibiotics work?
-prevent bacteria from making a normal cell wall (murein/peptidoglycan) by targeting 70s ribosomes
-bacteria are unable to resist osmotic pressure and the cells burst due to an increase in cell volume of water by osmosis
-viruses use host cells organelles to carry out metabolic activities so do not have any viral organelles to disrupt
-viruses also have a capsid (protein coat) rather than a murein cell wall so antibiotics can’t act on viruses like they do for bacteria
-as viruses spend most of the time within a host cell, they are out of reach for antibiotics
Describe AIDS
-it is not a pathogen so can’t be detected using antigens or antibodies, it can be screened for by checking the number of t helper cells
-it replicates using the body’s t helper cells, so HIV reduces an individual ability to respond to pathogens as their cell mediated immunity is compromised
-an uninfected person should have 800-1200 helper cells per m cubed of blood, an infected person ca have as few as 200
-screening elisa can detect HIV status in a patient
-
Does HIV directly kill people?
-no, but it compromises the immune system and leaves people vulnerable to secondary diseases that ultimately cause death
-B memory cells must be activated by t helper cells which have been destroyed
What symptoms may someone with AIDS have?
-infections of lungs, intestines, brain and eyes
-weight loss and diarrhoea
What happens if someone has more HIV?
-more HIV
-destruction of more T helper cells
-less activation of B cell
-less able to destroy infected cell
What happens if someone has less HIV?
-less HIV
-destruction of less T helper cells
-more activation of B cell
-more able to destroy infected cell
