A & P - Immune system Flashcards
what is an epitope?
the part of an antigen recognised by the immune system
what is the function of the immune system?
distinguishes the ‘host’ from everything foreign and protects against infection
what structures does the immune system recognise?
MAMPS - microbe-associated molecular patterns
describe innate immunity
targets - groups of pathogens
speed - rapid
no memory developed
describe adaptive immunity
targets - specific pathogens
speed - slow
memory to pathogens developed
describe the step involved in establishing an infection
- transmission of bacteria
- entry into body and colonisation
- obtain nutrients for growth
- evade host immune defences
- effects of host
- host response
what is lymphatic fluid and what is its function?
fluid containing white blood cells that helps rid the body of toxins, waste and other unwanted materials
how is lymphatic fluid moved around the body?
arm/leg muscles
respiratory muscles
rhythmic contraction of smooth muscle in lymphatic wall
name two types of cell associated with the immune system
lymphocytes
granulocytes
which cells are produced from lymphocytes?
B cells - plasma / memory cells
T cells - Th / Tc cells
natural killer cells
which cells are produced from granulocytes?
neutrophils
eosinophils
basophils
monocytes - dendritic cell / macrophage
what is the first stage of innate immunity?
physical barriers
what are the physical barriers of the skin against bacteria?
antimicrobials (sweat, sebum) - lactoferin
low pH
commensal bacteria
shedding
what are the physical barriers of the genitourinary tract against bacteria?
washing in urine
vaginal secretions
urine acidity
lysosome
what are the physical barriers of the gastrointestinal tract against bacteria?
stomach acidity intestinal pH normal flora mechanical flushing lysosomes
were are lysozymes found and why are they an important physical barrier it bacteria?
secretions - tears, saliva, human milk, and mucus
damage bacterial cell wall
lactoferrin is a protein found in tears and sweat, how does it help innate immunity?
protein binds to iron making it unavailable to bacteria
name the tissues of the immune system
thymus spleen bone marrow lymph nodes lymphatic's blood
name the molecules of the immune system
complement
inflammatory mediators (cell signalling molecules) - chemokines / cytokines
enzymes - lysozymes
name a cytokine important to innate immunity
interferon
describe the action of interferon
- virus infected cell produces interferon (IFN)
- IFN acts internally to protect infected cell
- IFN also secreted from cell - binds to nearby cells to trigger anti-viral response
what processes are used by the innate immune system to protect the body?
physical / chemical barriers
antimicrobial factors
specialised cells - phagocytes / natural killer cells
inflammation / fever
what are natural killer cells?
white blood cells and tissue dwelling cells - able to recognise and kill infected cells
what are phagocytes?
‘eating cells’ - white blood cells and tissue dwelling cells able to ingest and kill microbes
name three types of phagocytes and where they are found
monocytes - blood
tissue macrophages
neutrophils - blood
name three polymorphonuclear cells (PMNs)
neutrophils
eosinophils
basophils
which cells are the first to arrive at an infection site?
polymorphonuclear cells (PMNs)
describe polymorphonuclear cells (PMNs)
non-dividing, short lived <1day
multi-lobed nuclei
granule - chemical attack
what are eosinophils particularly good at targeting?
parasitic infection
why is inflammation an important part of the innate immune system?
local response helps to clear infection but wide spread response may lead to septic shock / death
what are the 5 signs of inflammation?
erythema (redness) heat swelling / oedema pain possible loss of function
describe the stages of the inflammatory / fever response
- tissue damaged, chemokines, cytokines, histamine released
- vasodilation - increased permeability of blood vessels
- neutrophils leak through blood vessel wall
- migration of inflammatory cells and clotting factors
what role does inflammation play in innate immunity?
vasodilation / increased permeability of blood vessels
accumulation of blood
leakage of clotting factors / clot formation
movement of neutrophils / macrophages - engulf microbes
death of phagocytes - pus produced
initiation of tissue repair
what role does fever play in innate immunity?
triggered by toxins / cytokines
high temp triggered by resetting hypothalamic thermostat
inhibits bacteria growth
speeds up enzyme reactions aiding repair
describe the timeframes of innate and adaptive immunity
innate - immediate (0-4hrs) preformed mediators
innate - early (4-96hrs) recruitment of innate immune cells
adaptive - late (>96hrs)
what are three characteristics of the adaptive immune system?
memory
specificity
discrimination between self and non-self
which cells belong to the adaptive immune system?
lymphocytes
the adaptive immune system uses two methods, what are these and which cells are involved?
antibody mediated immunity - B cells
cell mediated immunity - T cells
describe how a B cell is activated
- cell surface receptor recognises pathogen
- memory cells created which recognise pathogen in future
- initial B cell then differentiates to form plasma cell which produces specific antibodies for pathogen
describe how T cells are activated
- pre-cells all with different surface receptors
- antigen activates one cell with component for infecting antigen
- activated cell proliferates to form memory cells
- effector cells also produced which directly attack antigen
what is another name for an antibody?
immunoglobulin
what is the Fab region of the immunoglobulin for?
area which binds to the antigen
what does the Fc region of the immunoglobulin determine?
the type of antibody - eg. IgA, IgG, IgM
what happens at the variable region of the immunoglobulin?
differs in amino acid sequence to recognise different microbes
what does the flexible hinge region of the immunoglobulin allow for?
the antibody can adjust to accommodate for variable distances between antigen binding sites
name the 5 classes of antibody
IgM IgA IgG IgE IgD
what are the function of antibodies IgM and IgG?
IgM - 1st produced, blood antibody, fixes complement, acts as B cell receptor
IgG - blood and tissue antibody, fixes complement, binds phagocytes, neutralises toxins
what are the function of antibodies IgA, IgD and IgE?
IgA - secretory antibody, breast milk, protection of mucosa
IgD - membrane receptor
IgE - binds to mast cells and basophils, important in parasitic infection
name three ways in which antibodies protect from infection
- block binding od pathogen and toxins
- facilitate phagocytosis by macrophage / neutrophil
- kill bacteria by activating complement
how do antibodies block binding of pathogens and toxins?
antibodies form complexes with the pathogen/toxin - the antibody complex is then ingested by phagocytes
how do antibodies facilitate phagocytosis?
antibody forms a cell surface receptor on the macrophage or neutrophil which fits the antigen, enabling it to be phagocytised
what is a complement?
group of blood borne proteins activated after binding to antibody covered antigens
how does the antibody kill bacteria by activating the complement?
complement is activated by antibody on surface of antigen
when activated complement causes lysis of microbe
complement releases cytokines when bacteria binds
punches holes in bacteria
coats bacteria (opsonisation) for phagocytosis
in what ways do antibodies contribution the host resistance?
neutralises toxins
extracellular lysis of bacteria (complement)
facilitates internalisation for intracellular killing
expulsion of parasites via inflammatory response
what is Bruton’s disease?
X-linked hypogammaglobinaemia
what are the causes of Bruton’s disease?
failure of B cells to mature
absence of circulating B cells
reduced or absent immunoglobulins
what are the symptoms of Bruton’s disease?
failure to clear infection
recurrent respiratory/middle ear/skin infections
what are the functions of T lymphocytes?
kills virus infected cell (Tc (cytotoxic) cells)
resistance against intracelluer pathogens
activates macrophage
helps antibody response (Th cells)
immunoregulatory function
what do T cells receptors do?
recognise antigens bound to molecules (MHC) on surface of cell
where are MHC molecules found?
MHC I - on nucleated cell
MHC II - on antigen-presenting cell (APC)
name the two types of T cell
Tc (cytotoxic or killer) CD8
Th (helper) CD4
which MHC presents antigens to CD8 T cells?
MHC I
MHC I presents antigens of which origin?
intracellular
MHC II presents antigens of which origin?
extracellular
which MHC do the CD4 T cells deal with?
MHC II
what happens the cell when a MHC I presents the antigen to the CD8 T- cell?
the cell is destroyed
what happens the cell when a MHC II presents the antigen to the CD4 T- cell?
the CD4 T cell differentiates into effector T-cells
when the CD4 T cell differentiates what could follow?
helps B cells become plasma cells
helps CD8 cells become cytotoxic
activates macrophage
what disease occurs if the lymphocyte precursor cell isn’t present?
severe combined immunodeficiency disease (SCID)
what are the symptoms of SCID?
failure to thrive viral gastroenteritis viral chest infection parasitic infection bacterial septicaemia fungal urinary infection
what disease occurs if the T lymphocyte precursor or pre T cells are absent or decreased in number or function?
Di George Syndrome
what are the symptoms of Di George Syndrome?
variable antibody function IgM - normal to low IgG - low to absent increased susceptibility to viral, fungal and protozoan infections congenital development disorder
what happens if mature T lymphocytes are depleted?
HIV infection leading to AIDS
