immunology Flashcards
how does the skin contribute to preventing infection
composed of tight keratinised cells that are, has a low pH and O2 tension, secretes hydrophobic oils, lysozyme and antimicrobial peptides
how does mucous prevent against infection
lines body cavities in line with outside world (GI tract), traps bacteria, secretes antibodies
how do commensal bacteria prevent against infection
symbiotic with host, compete with fatty acids, produce toxins to other bacteria
describe the nature of the innate immune system
fast, non adaptive present since birth
what are the cells involved in the innate immune system
Macrophages, dendritic cells, NK cells, mast cells (neutrophils basophils, eosinophils)
what is the inflammatory response
increases body temp and attracts macrophages
describe the nature of adaptive immunity
slow, specific, from memory
describe macrophages
pink cytoplasm and kidney bean nucleus, develop from circulating monocytes, they phagocyte cells, reside in tissues, monocytes are precursors
describe dendritic cells
present in large numbers in tissues, are professional antigen presenting cells to T cells, phagocytes
describe natural killer cells
release cytotoxic molecules that kill infected cells by apoptosis, respond to MCH I
describe mast cells
reside in tissues, single nucleus, fight antibody-coated parasites, illicit inflammatory response by degranulation (histamine, TNF, IL)
how do innate immune cells recognise pathogens
pathogens express PAMPs and immune cells have receptors for his PRRs
what is the main function of phagocytosis, what are the main cells
to ingest and kill cells/ bacteria/ fungi. macrophages, neutrophils and dendritic cells
describe how phagocytosis works (up until debris release)
PRR recognises PAMPs, creates phagosome around target. fuses with lyososme (contains ROS) and kills pathogen, debris is released to EXC space
how do phagocytes ‘remember’ antigens
peptides from antigen are expressed on cell surface receptors MCH II
what else is released after phagocytosis
pro-inflammatory mediators TNFa
describe opsonisation
coating of pathogens in opsonins to aid phagocytosis
name some major opsonins
C3b, Fc of IgG, CRP
what happens to virally infected cells
release interferons (INFa/b), NKC’s can recognise
what happens when large parasites are present
too large to be phagocytosed, results in degranulation - pro inflammatory substances eg IFNy
what are the 5 types of leukocytes (WBC’s)
neutrophils, eosinophils, basophils, monocytes, lymphocytes
what are neutrophils for
initiation and upkeep of inflammation
what are the steps of transendothelial migration
margination of neutrophils to endothelium, bind to adhesion molecules and pass across endothelial by diapedesis. attracted to site of injury by chemotaxis, activated by PAMPs and TNFa
neutrophils kill pathogens in what 3 ways and what do they release
phagocytosis, degranulation, NETs - TNF when activated
how do neutrophils kill by phagocytosis
pathogens release chemokines, phagolysosomal or ROS-dependent killing which requires NADPJ
how do neutrophils kill by degranulation
release of anti-bacterial protein
how do neutrophils kill by NETs
activated neutrophils release intracellular structures that immobilise pathogens and facilitate phagocytosis
what is the acute phase response of innate immunity
liver releases proteins in response to pro-inflammatory mediators eg . (interleukines and TNF)
what proteins does the liver release
CRP, compliment proteins: C4, C3, C2
what is the complement system
creates a cascade reaction in response to inflammation and infected cells
what are the 3 complement pathways
classic, alternate, lectin
what is the classic complement pathway
antibodies cause conformational change in C1 which activates C3 –> C3a + C3b
what is the alternative pathway
C3b is unstable and so rapidly degreades back to C3 unless it binds, cells express inhibitory proteins to prevent C3b activated downstream events
what are the 3 components of the downstream compliment system
MAC, opsonisation, inflammation
what proteins make the MAC complex
C5-C9
what sequence of events activates MAC
C3b activates C5 –> C5a and C5b. C5b activates MAC
what is the function of C3a and C5a
attract macrophages for phagocytosis and are inflammatory mediators
what do cytokines
produced in response to inflammation/ infection and regulate cell behaviour for immune system
name some pro-inflammatory cytokines
TNF, interleukins
what do interferons do
viral infections
what do chemokines do
control cell migration
which cells are involved in acquired immunity
B cells and T cells
which is humoral
B cells
where are B cells developed
bone marrow
where are T cells produced
thymus
where is primary lymphoid tissue
bone marrow and thymus
where is secondary lymphoid tissue
spleen, tonsils, lymph nodes
what are antigens
specific structures on pathogens which allows them to be identifies
what do B cells produce and what are they
antibodies specific to antigens, are Y shaped glycoproteins and act as opsins
what are the immunoglobins produces in the blood from most to least abundant
IgG, IgA, IgM, IgD, IgE
where do T and B cells become activated
secondary lymphoid tissue
how do T and B cells enter the lymph node
transendothelial migration from high endothelial venules (HEV)
Once B cells are activated what happens
they clonally proliferate and differentiate to different cells: effector plasma cells (produce antibodies) or memory cells
what does IgG do
antibody immunity to developing foetus
what does IgA do
secretory: found in breast milk, blood, mucosal defense
what does IgM do
found in blood, first antibody produces
what does IgD do
unknown
what does IgE do
activates mast cells to cause degranulation (allergic response)
What cells produce MHC I and what do they present to
all nucleated cells, CD8+T cells
What cells produce MHC II and what do they present to
antigen presenting cells: dendritic, macrophages, B cells,.
activate CD4+T
what can CD4+T differentiate into
TH0, TH1, TFH
what does CD4+T release to cause it to differentiate into TH0, where does this occur
IL2, lymph nodes
What does TH0 differentiate into and what does this do
TH1, leaves lymph nodes and goes to inflamed tissue
what does TFH do
activates B cells in germinal centre of lymph nodes
what does CD8+ develop into
killing cells: cytotoxic T lymphocytes
how does CTL kill cells
migrates out of lymph nodes and binds to infected cells, inserts DNA for apoptosis.
what can activate B cells
IL4, Il5, IFNy
what do mast cells and basophils do
secrete inflammatory stuff eg histamine in allergic reaction
what is the lectin pathway
mannose binding lectin imitates C1 and activates C3
