Lecture 13 - The immune system Flashcards
describe the complexity of the immune system
highly complex, highly regualted, highly interactive system.
list an example of a tissue with specialized resident immune cells
- the skin has langerhans cells
- the brain has microglia and astrocytes
what are the primary lymphoid organs
- thymus
- bone marrow
- spleen
- lymph nodes
what is the role of bone marrow and the thymus in the immune system?
production of B and T cells in the bone marrow, maturation of T cells in the thymus
what is tolerance
recognize and ignore the body’s own cells and harmless substances, while still being able to attack harmful invaders like pathogens.
what does the IS recognise vs tolerise
recognises pathogens and foreign particles and tolerises self (unless its cancer cells or autoimmunity)
what are the two barrier types of the immune system?
biochemical defense and physical defense
what are the biochemical defenses?
- lysozyme in body secretions
- sebaceous gland secretions
- commensal organisms in gut and vagina
- spermine in semen
what are the biophysical defenses?
- mucus
- cilia lining respiratory tract
- acid in stomach
- skin (largest barrier)
what are the only adaptive immune cells of the IS
lymphocytes - B and T cells and plasma cells
true or false: there is the same composition of immune cell types all over the body
false, different types are required in different places at different concentrations
approximately 70% of blood immune cells are ________. the rest is made up of?
neutrophils.
t cells 60-70%
monocytes, NK cells and B cells
- hard to measure in living people
true or false: with innate immunity, immunity is improved by repeated infection
false
what are the features of innate immunity?
- rapid responses
- prevents infection spreading
- no memory cells are generated
describe the timeline of immune responses
tissue response in mins
phagocytosis in hours
antigen delivery to lymph nodes in days
detection by lymphocytes in days to weeks
memory cells formed in months to years
what are the features of adaptive immunity?
- immunity is improved by repeated infection/exposure
- antigen specific responses
- generation of antigen specific memory populations
what responses does the adaptive immune system control?
- B and T cell release
- antibodies production
- cytokines (produced by b and t cells, specific)
- vaccines target adaptive immune
what is an antigen?
a toxin or foreign substance which induces an immune response in the body
what are the main goals of the innate immune system
- respond early
- present antigens in a way that the adaptive immune system can recognise them
what are the main goals of the adaptive immune system
- highly effective and anitgen specific B and T cell production
- while not recognising self
- creation of memory
what are the key innate factors/processes?
- chemokines
- phagocytosis
- complement system
- DAMPs and PAMPs
- PRR (pattern recognition receptors)
describe the process of a local infection innate immune response
- bacteria recognised by cell wall components
- complement components and chemokine release
- activation of other complement proteins
- chemotaxis encourages neutrophil extravasation (increased vascular permeability of BV)
what are the most abundant phagocytes in the blood
neutrophils
- designed to rapidly deal with infection
describe the phagocytosis process
- adherence
- membrane activation
- particle engulfed
- phagosome formation
- fusion with lysosome
- release of degraded products (exocytosis)
how do phagocytes distinguish self from non self?
- receptors of various types
what receptors do phagocytes use to recognise pathogens?
- pattern recognition receptors
- opsonic receptors
- complement receptors
- scavenger receptors
- apoptotic receptors
describe pattern recognition receptors
- TLRs and CLRs
- detect a broad array of molecular patterns from bacteria fungi and viruses
describe opsonic receptors
- FcgammaRs
- receptors bind IgG anibodies
describe complement receptors
- CR1, CR3, CR4 bind specific complement proteins and a factors from the ECM and acute phase proteins
how does opsonisation cause phagocytosis?
bacteria cause complement release, and complement C3b binds to bacterial cell wall surface, recognised by phagocytic cells with complement receptors on their surfaces
