3.2.3 Cell Recognition and the Immune System Flashcards
How does the HIV virus replicate?
Attaches to receptor molecule on host cell membrane. Capsid is released into cell and it uncoats and releases nucleic acid. Reverse transcriptase is used to make a complementary strand of DNA from the viral RNA template. Double stranded DNA is made and inserted into the human DNA (using integrase). Host cell enzymes are used to make viral proteins from the viral DNA within the human DNA. The viral proteins are assembled into new viruses and releases from the cell via cell lysis
What is AIDS?
When the immune system deteriorates and eventually falls
How does the human body distinguish between self & non-self cells?
Marker molecules (proteins) are present on the membrane of cells, enabling the body to recognise these as ‘self’ cells.
What is a toxin?
A protein (antigen) released by pathogens which are poisonous to the body.
What is phagocytosis?
When foreign cells are engulfed by phagocytes, digested by lysozymes released by lysosomes in the cell.
Describe the role of T-helper cells.
Recruit & signal to phagocytes AND activate B cells
Describe the role of T-cytotoxic cells.
Kill abnormal & foreign cells (produces proteins to do this e.g. perforin)
What is a B plasma cell?
A type of B cell which secrete LOTS of monoclonal antibodies (all complementary to a specific antigen)
Describe the importance of the variable region of an antibody.
Has a unique protein structure, which provides specificity to one type of antigen.
What does the humoral immmune response consist of?
B cells- antibodies, clonal selection.
What does the cellular immune response consist of?
T cells- phagocytes, cell signals etc.
Describe the primary response of the immune system.
When the body first detects a type of pathogen, a slow response, which creates memory cells. The body will show symptoms until enough antibodies are made.
Explain why the secondary response is quicker than the primary immune response.
B- memory cells are activated and divide into plasma cells, producing antibodies. T-memory cells are activated and produce T-cells to kill the pathogen. FEWER STEPS!
What is active natural immunity?
When a person is immune, after naturally contracting an infection.
What is passive immunity?
When a person is immune, by being given antibodies rather than making them. e.g. natural from breastfeeding.
Give 2 differences between passive & active immunity.
Active- lasts longer, memory cells are produced, response takes longer to happen, needs antigen to trigger response.
What is a vaccine?
A low dose of an inactive/dead pathogen are injected- contain antigens to trigger immune response, creating protective memory cells.
What is herd immunity?
When more members of a population have had a vaccine/are immune, so more people are protected asthe disease can spread less rapidly, even if they haven’t had the vaccine themselves.
What is antigenic variation?
Where a pathogen can change the antigens on its surface (e.g. different strains of flu)
Explain why people must receive a different flu vaccine annually.
The flu virus undergoes antigenic variation, so memory cells from one vaccine will not always protect against new strains.
What are monoclonal antibodies?
Antibodies which are all made from identical B plasma cells- complementary to the same specific antigen.
Describe how monoclonal antibodies can be used in anti-cancer drugs.
Antibodies are specific to antigens on cancerous cells (tumour markers)- the drug bind s& accumulates in specific area (much fewer side effects than conventional cancer treatments).
What is an ELISA test?
Where antibodies are attached to an enzyme, which produces a coloured substrate- used in diagnosis.
Which part of the immune system does HIV initially affect?
T cells
Explain why antibiotics cannot be used on HIV.
Antibiotics are specific to bacteria e.g. murein cell walls, so would be ineffective on viral structure.
Why is aseptic technique important?
prevents contamination of cultures by unwanted microorganism
What is phagocytosis?
Phagocyte recognises the antigens on a pathogen. endocytosis. pathogen is contained in a phagocytic vacuole. lysosomes, containing digestive enzymes fuse with the vacuole, enzymes are released and they destroy the pathogen. phagocyte presents antigen on its surface
What do the receptors on T cells do?
bind to antigens displayed by antigen presenting cells
How are T cells activated?
When their receptors bind to complementary antigens on the surface of antigen presenting cells. once activated by this binding each t helper cell produces a clone of active t helper cells and a clone of t memory cells
Describe the antibody structure
Four polypeptide chains, 2 heavy and 2 light. each chain has a variable region and a constant region
State the variable region on an antibody
Form the antigen binding site. The shape is complementary to a particular antigen, its shape varies between antibodies
What are B memory cells?
They bind to the antigen. They remain or months or years in the body, enabling the individual to respond more quickly to the same antigen in the future.
If the zone of inhibition is wider, what does this indicate about the antibiotic?
the wider the clear zone, the more effective the antibiotic is at preventing growth
