BIOL 435 Ch. 1 (Overview of the Immune System) Flashcards
immunity
-state of protection against foreign pathogens or substances (antigens)
>sometimes not foreign (ex. cancer)
-“exempt”
observations of immunity
- go back over 2000 years
- noticed that those recovered from the plague could safely nurse the currently ill
vaccination
- prepares the immune system to eradicate on infectious agent before it causes disease
- widespread use has saved many lives
ex. rabies vaccination and eradication of small pox
Louis Pasteur
- ‘old’ (attenuated) bacteria into chickens and didn’t die
- could inoculate and prevent disease
virulation
- dried puss into cuts
- became immune by getting a milder case
attenuation
-weakened strength or ability to cause disease
immune system components
- Innate
- Adaptive
* don’t work independently
innate immunity
-very fast (minutes to hours)
-limited and fixed
-same response each time
Major components:
-barriers (eg. skin)
-phagocytes
-pattern recognition molecules
-can work independently
adaptive immunity
-slower response
-highly diverse and adapts
-different response each time (more rapid and effective)
-can’t work independently
-not in everyone
Major components:
-T and B lymphocytes
-antigen-specific receptors
-antibodies (Ab)
cooperatively
- innate and adaptive immunity
- activation of innate(+adaptive) produces signal molecules (cytokines and chemokines:’trail of bread crumbs’)
- these molecules stimulate and direct adaptive immune responses
innate immune responses
-first line of defence
>fast, relatively nonspecific
-uses germ-line encoded (inherited) pattern recognition receptors (PRR)
-also uses phagocytic cells
PRR
- pattern recognition receptors
- bind to PAMPs
- target something that will always be on pathogens
PAMPs
- pathogen-associated molecular patterns
- generic molecules found on many different types of pathogens
- eg. peptidoglycan
adaptive immune responses
- Humoral responses (B-cells)
- Cell-mediated responses (T-cells)
- slower to develop (5-6days)
- use randomly generated antigen receptors
- highly specified to individual antigen molecules
randomly generated antigen receptors
-these bind to very specific antigens, rather than molecules found on many pathogens
>ex. bind to a single component of peptidoglycan
memory
- the hallmark of adaptive immunity
- NOT present in innate immunity
primary response (memory)
- initiated upon first exposure to an antigen
- memory lymphocytes are left behind after antigen is cleared
secondary response (memory)
- initiated upon second exposure to the same antigen that stimulates memory lymphocytes
- stimulation yields faster, more significant, better adaptive response
humoral immunity
- combats pathogens via antibodies (Ab)
- Ab produced by B-lymphocytes
- Ab can be transferred between individuals to provide passive immunity
cell-mediated immunity
-involves primarily T lymphocytes
>can eradicate pathogens, clear infected self-cells or aid other cells in inducing immunity
surface receptors
- used in humoral and cell-mediated immunity
- B-cell receptors (BCR)
- T-cell receptors (TCR)
- randomly generated by gene segment rearrangements in B and T cells (rearranging the DNA)
- once released from membrane=Ab
B-cells encounter antigen
-produce antibodies matching the specificity of their BCR
>cell membrane immunoglobin
T-cell receptors
-bind specific peptides displayed on the surface of other cells
>peptides must be bound to special presentation molecules called MHC (self) and peptide (non-self)
-positive and negative selection
individual B and T cells
- have an individual specificity for a single antigen
- due to having many copies of a receptor on their surface that only binds to one type of antigen
B- and T-cell interacts with unique antigen
-it is selected and becomes activated
>results in a proliferation (producing a large number of clones)
each clone
- reactive against the same antigen that initially stimulated the original lymphocyte
- each produces antibodies and releases them to fight the pathogen
4 major categories of pathogens
-viruses
-bacteria
-fungi
-parasites
*immune responses are quickly tailored to the type of organism involved
>depends on structure of pathogen and location
SARS-CoV-2
-severe acute respiratory syndrome coronavirus 2
tolerance
- ensures that the immune system avoids destroying host tissue
- helps keep anti-self recognition molecules (due to random rearrangement) from circulating in bloodstream
negative selection process
- cells too reactive to ‘self’ are culled
- important that it works, otherwise we get auto-immunity
tolerance mechanisms
- any cells or receptors that respond to self are eliminated
- host should always know difference between self and non-self
- danger/damage vs. safe (not as much self vs. non-self)
dysfunctions of immunity categories
- Overly active
2. Immunodeficiency
overly active
- or misdirected immune response
- allergies
- asthma
- autoimmune disease (eg. MS, Crohn’s)
immunodeficiency
- primary loss of immune function (genetic)
- secondary loss of immune function (acquired)
secondary (acquired) loss of immune function
- opportunistic infections can occur in people with impaired immune responses
ex. oral thrush and HIV
transplanted tissues
- a rare case where we want to AVOID an immune response
- don’t want rejection
- body’s natural response to foreign tissue is to attack it and destroy it
cancer
- situation where the dangerous cells we want to target are our own self-cells
- generally tolerated and hard to generate immunity against
the microbiome
- community of commensal organisms that live in and on us the cause no harm
- function in homeostasis (metabolic and immune balance)
imbalance or dysbiosis
- leads to immune overstimulation resulting in inflammation
- due to dietary changes or environmental factors (ex. stress)
inflammation
-cause of many things >CVD >diabetes >obesity >allergies
symbiosis
-gut barrier integrity
-gut-brain-immune homeostasis
>balanced immune function
>neurologic homeostasis
>metabolic regulation
antigen (Ag)
- any molecule that will specifically stimulate B- and T- cells and produce an adaptive immune response
- general: anything that produces an immune response
humoral
-blood borne
passive immunity
- not very long
- not as good as active immunity
ex. injecting antibodies into a human to treat a snake bite
