3.2.4 Immunology Flashcards
What is a pathogen?
- Microorganism (bacteria, virus, fungi)
- That causes disease
What is a non specific defense mechanism?
Doesn’t distinguish between pathogens/ responds the same way to all pathogens
How does a pathogen cause disease after entering the body?
- Produces toxins
- Damages cells
Describe how antibodies are produced in the body following an infection
- Virus contains antigen
- Virus engulfed by phagocyte
- Presents antigen to T cells / T helper cells which secrete cytokines
- Specific B cell becomes activated
- Divides to form clones
- By mitosis (in clonal selection and expansion)
- Plasma cells produce and secrete antibodies
- Which are specific to the antigen
- Memory cells formed
Describe how a pathogen is destroyed by phagocytosis
- Phagocyte attracted by a substance or chemical/ binds to antigen
- Engulfs pathogen
- Into vesicle/phagosome
- Lysosome fuses with phagosome
- And releases hydrolytic enzyme (eg lysozyme)
- Which hydrolyses the pathogen
- Antigen is presented on the cell surface membrane of the cell - it is an antigen presenting cell
Antigen definition
Foreign protein
which triggers an immune response - production of antibodies
Description of active immunity
- Immunity gained from antibodies produced by the immune response (after a pathogen / antigen enters the body)
- Memory cells made
Description of passive immunity
- Immunity gained without an immune response (body is given the antibodies)
- No memory cells
Natural immunity description
Immunity gained by being infected (active) or receiving antibodies from the mother across the placenta or breast milk (passive)
Description of artificial immunity
Immunity gained either by vaccination (active) or injecting antibodies (passive)
Aside from pathogens what types of cell stimulate an immune response?
- Transplanted cells/cells from other organisms
- Virus infected cells
- Cancerous cells
Describe the difference between active and passive immunity (6)
- Active involves memory cells, passive doesn’t
- Active involves production of antibody by plasma cells/ memory cells
- Passive involves antibody introduced into body from outside/ named source
- Active long term because antibody produced in response to antigen
- Passive short term because antibody is broken down
- Active can take time to develop, passive fast acting
Uses of monoclonal antibodies in medical treatments (*2)
- Targets/carries/binds drug to specific cells/antigens/receptors
- Block antigens/receptors on cells
How do antibodies stimulate phagocytosis?
Bind to antigen (are markers) and cause agglutination (clumping) /attract phagocytes
Role of antibodies (*2)
- Agglutination of cells - easier for phagocytes to locate
- Act as markers that stimulate phagocytes to engulf the bacterial cells
How are antibodies specific to an antigen?
- Antibody variable region has specific amino acid sequence/primary structure
- Shape/tertiary structure of the binding site
- Is complementary to these antigens
- (Binds and) forms antigen-antibody complex
What is the difference between cellular and humoural immune response?
Humoural immunity produces antigen-specific antibodies, cellular doesn’t.
Antibodies, T cells, B cells = humoural
Phagocytes = cellular
What are the 2 types of white blood cells?
- phagocytes (non-specific)
- lymphocytes (B cells/B lymphocytes, T cells, memory B cells7)
Antibody definition, monoclonal antibody definition
- A protein specific to an antigen produced by B cells/ secreted and released by plasma cells
- antibodies produced from a single clone of B cells/plasma cells or the same B/plasma cell
Description of secondary immune response
- higher concentration of antibodies
- produced more quickly
- due to memory cells
How do vaccines protect people from disease?
- vaccine contains antigens
- dead/weakened pathogens
- memory cells produced
- on second exposure more antibodies are produced more rapidly
- antibodies destroy pathogens
- herd immunity/ fewer people to pass on the disease
Describe how a positive result is produced in an ELISA test
- antibodies attached to plate
- first antibody binds to antigen to form antigen - antibody complex because they’re complementary
- plate washed to remove unbound antibodies
- second antibody with enzyme attached is added
- second antibody attaches to antigen
- plate washed to remove unbound antibodies
- substrate added to cause colour change due to enzyme
Describe how HIV causes the symptoms of AIDs
- HIV destroys T helper cells
- more viruses produced leads to fall in T cells
- so fewer T cells to activate B cells
- reduced antibody production
- immune system not working properly - person more prone to opportunistic infections/cancer
- eg cancer, TB, pneumonia
Why are antibiotics ineffective against viruses?
- antibiotics stop metabolism, viruses don’t have metabolism
- some antibiotics work against (eg ribosomes) which viruses don’t have
- viruses hide in cells were antibiotics can’t reaxg
What does attenuated mean?
- microorganism alive
- but does not cause symptoms of a disease
