L3 - adaptive response Flashcards
innate mechanisms
rapid response to a broad range of microbes
innate external defences
skin, mucus membranes and secretions
Innate internal defences
phagocytic cells, antimicrobial proteins, inflammatory responses and natural killer cells
Adaptive mechanisms
slower responses to specific microbes
Adaptive humeral responses
antibodies
adaptive cell-mediated response
cytotoxic lymphocytes
difference between innate and adaptive
innate = cobstant adaptive = for when there is a breach
Respiratory infections account for more than ?% of the global burden of human disease
6%
Adaptive immunity is a …
protective response to antigens from pathogens
but overactivity can cause excessive inflammation
Antigens
molecule usually made of proteins or carbs
capable of inducing an adaptive immune response
pathogens
covered in a myriad of unique antigens which are recognised as foreign
antigen-presenting cells are AKA…
aka dendritic cells!!
Antigen-presenting cells
raise the alarm, sends processes out to ‘taste’ the environment and phagocytose foreign material, process and present the antigen
then migrate to lymph nodes so T lymphocytes may recognise the antigen which activates them
lymphocytes
adaptive effector cells
T cells
cytotoxic T cells and T helper cells
Cytotoxic T cells
killer cells
T helper cells
produce cytokines
B cells
produce antibodies
(3) properties of adaptive immune response
ability to mount specific responses to a huge range of pathogen-derived antigens
avoids reacting to self-antigens - self-tolerance
development of immunological memory
Constant region
anchors receptor to the cell (B or T)
Variable region
only acts with a specific antigen via lock and key method
somatic hypermutation
Subsequent exposure to an antigen during infection triggers lymphocyte proliferation with inaccurate DNA replication, generating further replication
DNA-encoding B and T cell receptors contain..
multiple different variable, diversity and joining segments
in every lymphocyte all but one of each region is deleted, the remaining segments are all linked together
VDJ recombination
variable-diversity-joining recombination
breakages do not occur when a region is deleted, therefore increasing diversity
When a receptor recognises an antigen…
the lymphocyte expressing the receptor is triggered to proliferate
Variable region DNA
is unstable and prone to mutation during rapid cycles of cell division therefore further diversity - somatic hypermutation again
Affinity maturation
clones recognising the antigen more effectively are selected to survive above those which bind less effectively
Immune tolerance
state of unresponsiveness of the immune system to antigens that normally have the capacity to elicit an adaptive immune response
Tolerance can be..
to self and the foetus during pregnancy
can develop to pathogens through chronic infections and cancers
Failure to establish tolerance
can lead to autoimmune disease
B cells are from
bone marrow
T cells are from
thymus