Defense Mechanisms Flashcards
Describe the two stages of human immune response.
Stage 1 - Cell mediated immunity
- pathogens either invade body cells or are taken in by phagocytes.
- phagocyte presents antigens on it’s cell-surface membrane.
- the receptors from a specific TH cell fit exactly onto the antigen.
- the attachment stimulates the TH cells to undergo mitosis, producing identical clones.
- theses cloned cells either, become memory cells, or more TH cells which then either stimulate b cell mitosis, stimulate phagocytosis, or active TC cells.
Stage 2 - Humoral immunity
- B cells undergo mitosis after stimulation from TH cells.
- these cloned B cells either become plasma cells which secrete antibodies leading to the destruction of the pathogen by agglutination, or become memory cells.
Describe the process of phagocytosis.
- pathogen releases chemical products, attracting the phagocyte to move along a concentration gradient towards it.
- receptors on the phagocytes cell-surface membrane recognise and attach to chemicals on surface of pathogen, where the phagocyte engulfs the pathogen to form a phagosome.
- lysosomes in the phagocyte migrate towards the phagosome, fusing with it to form a phagolysosome.
- lysosomes release lysozymes into the phagolysosome which break down/digest the pathogen into waster material, which is removed from the cell by exocytosis.
What are the two types of lymphocyte?
(where they mature, where produced, what immunity associated with?)
T Lymphocytes -
- produced by stem cells in the bone marrow.
- mature in the thymus gland.
- associated with cell-mediated immunity.
B lymphocytes -
- produced by stem cells in the bone marrow.
- mature in the bone marrow.
- associated with humoral immunity.
How do Cytotoxic T cells work in the immune response?
- They kill infected cells by producing a protein called performing which makes holes in the cells membrane.
- This causes the cell membrane to become fully permeable to all substances, resulting in the cells death.
Name 4 non-specific mechanisms of humans barriers to disease.
Epidermis of skin -
- layers of dead cells prevent infection.
Mucus membrane -
- protective music layer secreted by goblet cells to trap invaders.
Ciliated epithelia -
- sweeps invaders away so they can be removed.
HCl in stomach -
- low pH to denature pathogens enzymes.
Describe the structure of an antibody.
- ‘Y’ shape.
- contains two heavy chains, and two light chains.
- has an antigen binding site at the open end of the ‘Y’ shape, which is a variable region, the rest of the body of the antibody being the constant region.
- has a receptor binding site on the ‘closed/single’ end of the ‘Y’ shape.
- made of four polypeptide chains.
What are 5 uses of monoclonal antibodies?
- targeting medication to specific cells by attaching a therapeutic drug to an antibody.
- preventing the uncontrolled growth/division of cancer cells by blocking chemical signals from the cancer cells once attached to the cells receptors.
- indirect monoclonal antibody therapy by attaching a radioactive or cytotoxic drug to the antibody, to allow them to be attached to cancer cells and kill them.
- diagnosing influenza, hepatitis, and chlamydia very quickly.
- can produce pregnancy test results quickly.
Name some ethical issues behind monoclonal antibodies.
- their creation requires deliberately inducing cancer in mice.
- some treatments have resulted in deaths of patients.
- safe testing of them have many risks associated with them.
Describe the structure of HIV Virus.
- contains reverse transcriptase and RNA surrounded by a capsid (protein coat).
- the capsid is surrounded by a matrix, which has a lipid envelope surrounding it, containing attachment proteins on the surface of the envelope.
How does HIV replicate?
Viral replication;
- HIV particle binds to host TH cell with attachment proteins.
- It releases its viral RNA into the host cell, which undergoes reverse transcriptase to become DNA.
- The viral DNA integrates into the host cell DNA.
- This causes the host cell to produce viral proteins and genomes.
- These are assembled into new HIV particles.
How does the ELISA test detect the presence and quantity of a protein in a sample?
Reaction site;
- free antibodies with specific binding sites bind to any of the antigen in the urine sample added. wash to remove any unbound antibodies.
- the free antibodies will travel along the test to the test site.
Test site;
- different fixed antibodies containing dye substrate and specific to antigen are present.
- any free antibodies with antigen will bind to fixed antibodies, causing colour change, any not stopped will travel to control site.
Control site;
- other different fixed antibodies specific to empty binding site on free antibodies, contains dye substrate, are present.
- any remaining free antibodies will bind to these, inducing a colour change.
How does HIV cause AIDS symptoms?
Why are antibiotics ineffective?
- by killing or interfering with the normal functioning of the TH cells.
- this reduces the immune systems efficiency greatly.
- viruses rely on hosts cells to carry out their metabolic processes, so don’t contain any of their own metabolic pathways and cell structures.
- therefore no metabolic pathways or cell structures for the antibiotics to disrupt.
What is the difference between Indirect and Direct detection using the ELISA test?
Indirect - unnamed antibody attaches to antigen, then another antibody attaches to unnamed antibody, inducing a colour change.
Direct - complementary antibody attaches to antigen and induces a colour change.
What are the main features of a successful vaccination programme?
- suitable vaccine must be economically available in sufficient quantities to immunise most of the vulnerable population.
- there must be few side effects if any to prevent putting people off getting vaccinated.
- means of producing, storing and transporting the vaccine must be available.
- must be means of appropriately administering the vaccine.
Name some differences between Passive and Active immunity.
Passive -
- produced by introduction of antibodies into individuals by outside source.
- no direct contact with pathogen or antigen is required to provide immunity.
- short lived immunity due to lack of memory cells produced as antibodies aren’t replaced when broken down as they are ‘foreign material’.
Active -
- produced by stimulating the immune system to produce it’s own antibodies.
- direct contact with pathogen or antigen is required.
- immunity takes longer to develop however is long-lasting.
