15 - introduction to immunity Flashcards
what is immunity?
the ability of an organism to resist a particular infection or toxin by the action of specific antibodies or sensitised WBCs
how do we gain immunity?
ACTIVE
• natural - natural infection
• artificial - immunisation
PASSIVE
• natural - placental transfer of maternal IgG
• artificial - human IgG
what are the 2 types of immunity?
innate
adaptive/acquired
what is innate immunity?
- present from birth
- simple recognition systems
- limited capacity
- there before infection starts
- patrols for infection
- rapid response - minutes
- no immunological memory
what is adaptive/acquired immunity?
- not present from birth
- learns from invading organisms
- sophisticated - highly specific recognition
- specific memory
- slower response - days
what is SCID?
severe compromised immunodeficiency
not born with innate immunity
goal of the immune system
- to clear potential pathogens in a controlled and efficient process
- minimal side effects
- no pathology in host
- appropriate duration
- return to homeostasis
- future protection
- no self attack
- remove potential tumours
factors affecting our immunity?
- general health
- infection
- nutrition
- adverse environmental conditions
- state of microbiome
- pregnancy
- genetic disorders
what is a vaccine?
a substance used to stimulate the production of antibodies and provide immunity against 1 or several diseases
prepared from the causative agent of a disease, its products, or a synthetic substitute, treated to act as an antigen without inducing the disease
exposure to the antigen causes an immune response which will protect you in the future
what is herd immunity?
immunising the majority of the population
susceptible people are indirectly protected
why is there no vaccine for malaria?
- costs
- logistics
- time
- complexity
4 main groups of vaccines
- live
- inactivated
- attenuated
- subunit
live vaccines
small amount of a live virus
eg. MMR
inactivated vaccines
organisms are dead but whole organism injected
attenuated vaccines
live organism but has its virulence removed
eg. smallpox
subunit vaccines
little bits of the virus/bacteria used to cause an immune response
cheapest and most efficient way
eg. meningitis
immunity can either by humoral or cellular, whats the difference?
humoral - in the blood (antibodies)
cellular - in the cells of the immune system
what are antibodies?
produced by plasma cells which are mature B lymphocyte cells
what is clonal selection?
- a single progenitor cell gives rise to a large number of lymphocytes, each with a different specificity
- removal of potentially self-reactive immature lymphocytes by clonal deletion
- pool of mature naive lymphocytes
- proliferation and differentiation of activated specific lymphocytes to form a clone of effector cells
cells of the immune system
all start as pluripotent stem cells
common/myphoid differentiates into T cells, B cells, NK cells and ILC
- B cells produce antibodies
- T cells are antigen specific
- NK cells and ILC are not specific and cannot recognise antigens - part of the innate response as they cannot adapt
what do monocytes do?
monocytes circulate in the blood and differentiate into macrophages in the tissue
what are primary lymphoid tissues?
central lymphoid organs
•bone marrow
• thymus
produce and mature lymphocytes
bone marrow
a soft, spongey, highly cellular tissue that fills the internal cavity of bones
produces B cells and T cell precursors (virgin lymphocytes)
thymus
a 2 lobed organ
produced T cells
only 2-4% mature and exit the thymus
what are secondary lymphoid tissues?
peripheral lymphoid tissues •lymph nodes • spleen • tonsils • mucosal associated lymphoid tissues (MALTs)
lymphocytes recirculate and if they meet antigen, unto clonal expansion and differentiate in the tissues
circulate in fluids - blood and lymph
adaptive immune responses occur in the secondary lymphoid tissues
where do B cells start to proliferate?
in the germinal centres of lymph nodes
what is MALT?
mucosal associated lymphoid tissue
a diffuse system of non-encapsulated, submucosal lymphoid tissue in the intestinal and respiratory tracts
respiratory MALTs
- nasopharyngeal lymphatic tissues (tonsils and adenoids)
* bronchus associated lymphatic tissue
intestinal MALTs
- Peyer’s patches
- appendix
- isolated follicles in intestinal mucosae
different effector mechanisms depend on:
- type of pathogen
- localisation
- stage of infection
- challenge
