immunology Flashcards
Describe the non-specific defence mechanisms the body may launch against pathogens (5 marks)
- Pathogen is engulfed by the phagocyte.
- Engulfed pathogen enters the cytoplasm of
the phagocyte in a vesicle; - Lysosomes fuse with vesicle releasing
digestive enzymes; - Lysosome enzymes break down the pathogen.
- Waste materials are ejected from the cell by exocytosis;
Describe how a phagocyte destroys a pathogen present in the blood.
- Engulfs;
- Forming vesicle/phagosome and fuses with lysosome;
- Enzymes digest/hydrolyse;
Give two types of cell, other than pathogens, that can stimulate an immune response.
- (Cells from) other organisms/transplants;
- Abnormal/cancer/tumour (cells);
- (Cells) infected by virus;
When a vaccine is given to a person, it leads to the production of antibodies against a disease-causing organism. Describe how
- Vaccine contains antigen from pathogen;
- Macrophage presents antigen on its surface;
- T (helper) cell with complementary receptor protein binds to antigen;
- T cell stimulates B cell;
- (With) complementary antibody on its surface;
- B cell divides to form clone secreting / producing same antibody;
- B cell secretes large amounts of antibody;
Explain how the humoral response leads to immunity.
- B cells specific to the antigen reproduce by mitosis.
- B cells produce plasma and memory cells
- Second infection produces antibodies in larger quantities AND quicker.
Describe the difference between active and passive immunity.
- Active involves memory cells, passive does not;
- 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 (given) is broken down;
- Active (can) take time to develop/work, passive fast acting;
State why some antibodies are referred to as monoclonal
(Antibodies) produced from a single clone of B cells / plasma cells;
OR
(Antibodies) produced from the same B cell / plasma cell;
Tests using monoclonal antibodies are specific. Use your knowledge of protein structure to explain why.
- Specific) primary structure / order of amino acids;
- (Specific) tertiary / 3D structure / shape;
- (So) Only binds to / fits / complementary to one antigen;
Describe the structure of the human immunodeficiency virus (HIV).
- RNA (as genetic material);
- Reverse transcriptase;
- (Protein) capsomeres/capsid;
- (Phospho)lipid (viral) envelope OR Envelope made of membrane;
- Attachment proteins;
HIV replication
- Protein on HIV binds with a protein commonly found on TH cells.
- Capsid fuses with cell-surface membrane and releases Viral mRNA and enzymes into the helper TH cell.
- The HIV’s reverse transcriptase converts viral mRNA into cDNA using host nucleotides.
- Viral cDNA moves into nucleus of T cell and is inserted into host cell genome (DNA). The person is now INFECTED.
- Transcription and translation of this DNA occurs so the T cell starts to manufacture HIV particles.
Describe how a person infected with HIV will develop AIDS (if untreated) and die of secondary infections.
- High viral load leads to increased destruction of helper T/CD4 cells;
- Less activation of B cells/cytotoxic T cells/phagocytes;
- Less production of plasma cells/antibodies OR (With cytotoxic T cells) less able to kill virus infected cells;
- (More able to) destroy other microbes/pathogens OR (More able to) destroy mutated/cancer cells;
Describe the role of antibodies in producing a positive result in an ELISA test.
- (First) antibody binds/attaches /complementary (in shape) to antigen; 2. (Second) antibody with enzyme attached is added;
- (Second) antibody attaches to antigen;
- (Substrate/solution added) and colour changes;
