1. Intro Flashcards
Function of immune system
Identify and eliminate harmful microorganisms/ substances
How does the immune system function?
Distinguishing ‘self’ from ‘non-self’ (or ‘normal self’ from ‘abnormal self’ in cancer)
Identifying ‘danger’ signals, inc. tissue damage
Immunopathology
Damage to host caused by immune system
Pathogens replicate much faster than humans, so can evolve faster
Humans must have flexible and rapid immune response
Immune system uses 2 strategies to recognise danger
- Uses pattern recognition receptors
2. Uses antigen-specific receptors on lymphocytes
Pathogen-Associated Molecular Patterns
Patterns that aren’t on our normal cells and can be recognised e.g. Peptidoglycan’s in bacteria
Damage-Associated Molecular Patterns example
Necrosis: Release a of cell contents e.g. nuclear components
=sign of tissue damage
Antigen-specific receptors on lymphocytes
- Each antigen receptor binds to a particular site (epitope) on a different antigen
- Each clone of B cells or T cells has a unique receptor, specific to 1 antigen; each cell carries many copies of this receptor on cell surface
Innate Immunity uses which strategy
Strategy 1- PRRs
Innate Immunity characteristics
Independent of previous exposure
Depends on pre-formed & rapidly synthesised components
Fast
Limited specificity
Acquired immunity uses which strategy
Strategy 2- antigen specific receptors on lymphocytes
Acquired immunity characteristics
An adaptation to exposure (aka acquired immunity)
Depends on clonal selection: i.e. expansion of cells/ antibodies, selected for antigen specificity
Slow
Highly specific
Acquired immunity effector arms
Cellular immunity (lymphocytes themselves) Humoral immunity (soluble effectors- antibodies for adaptive immune responses)
What does innate response do?
Destroys invading nucleic acids (e.g. viruses) in cytoplasm
Activates inflammatory pathways, signals for recruitment of immune system cells to sites of damage/infection
Elicits type 1 interferons (interfere with virus replication), for anti-viral defence
2 Main consequences of Innate response
“Buys time” while adaptive immune response starts
Promotes and directs appropriate adaptive immune response
Cells in Innate response
Neutrophils
Macrophages
Eosinophils
Cells in Adaptive response
B Lymphocytes
T Lymphocytes
Cells in both responses
Basophils/ mast cells
Dendritic cells
Natural killer cells
Soluble factors in Innate response
Acute phase proteins
Cytokines
Complement
Soluble factors in Adaptive response
Antibodies
Cytokines
Generation of clonal diversity in lymphocytes
During B and T cell development, random genetic recombination’s occur within each cell among multiple copies of immunoglobulin gene segments or TCR gene segments
clonal selection
Antigen binds to surface receptor on B or T cell and causes selective expansion of that clone
What happens when the antigen is removed?
Most lymphocytes that have proliferated will die after fulfilling their function
Some survive as memory cells: basis of vaccination
Re-exposure to a previously encountered antigen leads to a more rapid and greater immune response
