Immunology Flashcards
how does the skin protect from infection 3
physical barrier - tight packed cells
low pH
secretion of hydrophobic oils, lysozymes, defensins via sebaceous glands
how does commensal bacteria fight infection
produce anti-microbial short chain fatty acids, these:
compete for nutrients
reduce pH of bowel
synthesise vitK/B12
cells involved in innate immune system, purpose of innate
mast cells NK cells Phagocytes (complement) responsible for acute inflammation and killing of pathogen
how does the cells involved in the innate response detect pathogens
Pattern Recognition Receptors (PRRs) detect Pathogen-Associated Molecular Patterns (PAMPs)
4 examples of phagocytes
function
source of what
neutrophils, monocytes, macrophages and dendritic cells
ingest and kill bacteria
source of cytokines
t/f NK cells are a type of lymphocytes
true
what is released in degranulation of mast cells, effect of each (2)
histamine - inc permeability, incr blood flow, vasodilation of vessels and constriction of smooth muscle
tryptase - mast cell activation
mast cells, basophils and eosinophils are al granular cells, how do they differ
mast cells found in tissue and protect mucosal surfaces
basophils and eosinophils circulate in blood
3 mechanisms used by neutrophils to attack pathogens
phagocytosis
antimicrobial peptide and degradative proteases released
generate extracellular traps
what 3 things makes up pus
dead/dying neutrophils + tissue cells microbial debris
monocytes
precursors of macrophages/ dendritic cells
dual responsibilities of monocytes and macrophages
limit inflammation
tissue repair/wound healing
what does active neutrophils produce, what does this do
TNF-alpha (cytokine)
other than killing pathogens, function of macrophages
clear debris
inflammation
tissue repair and wound healing
dendritic cells are immature cells in peripheral tissues, however what happens when they come in contact with a pathogen
mature and migrate to secondary lymphoid tissues, are antigen presenting cells and stimulate adaptive immune response
functions of macrophages 5
ingest/kill extracellular pathogens clear debris from dead tissue cells inflammation tissue repair and wound healing antigen presentation
which cells specifically kill tumour and virally infected cells
NK cells
these also kill antibody-bound cells
CD8+, name and function
cytotoxic T cells
kill virally infected body cells
effector/memory
CD4+, name and function
helper T cells
regulators, activate other immune cells
primary site of leukocyte developement
(lymphoid tissue)
red bone marrow
thymus (until 12years)
3 examples of secondary lymphoid tissue, what is this the site of
lymph nodes
tonsils spleen
adaptive immune response initiated
how is direct communication carried out in the immune system
ligand interactions - receptors
how is indirect communication carried out in the immune system
production and secretion of cytokines
4 examples of types of cytokines
interferons
TNF
chemokines
interleukins
function of TNF
pro-inflammatory
which cytokine has anti-viral functions
interferons
which cells control and direct cell migration
chemokines
interleukin cells which is anti-inflammatory
IL-10
IL2 cells are said to be T cell proliferators, what does this mean
cause the increase in number of T cells
local effects would be redness,heat, swelling, pain and loss of function. what would be the systemic effect
fever
3 examples of pro-inflammatory cells
(remember cytokines)
IL-1
IL-6
TNF
which organ produces the pro-inflammatory cytokines in acute phase
liver
associated cells of innate immune system
macrophages mast cells neutrophils NK cells basophils eosinophills dendritic cells (complement system)
associated cells of adaptive immune system
T cells
B cells
dendritic cells
antibodies
one of the functions of the complement is opsonisation, what is this
coating of microorganisms by immune proteins (opsonins)
- C3b, CRP, antibodies
to enhance phagocytosis
what are antibodies
cells produced in the adaptive immune response which bind to pathogens to enhance phagocytosis (opsonisation)
during complement mediated lysis, C5b binds to pathogen surface, and C6,C7,C8,C9,C5b make up the membrane attack complex, what is this, what activates it
MAC (also called terminal complement complex TCC)
forms transmembrane channels, leading to targeted cell lysis (wall degredation) and death
activated by either classical/lectin/alternative pathways
other than mediated lysis and opsonisation, give 3 other functions of complement system
chemotaxis
clearance of immune complexes
inflammation
how does the complement systemm mediate inflammation and chemotaxis
C3a and C5a bind to receptors on mast/basophils ect which releases histamine and chemokines
outline structure of T and B cell antigen receptors
T cell - membrane-bound protein heterodimer
has alpha and beta chain
B cell - membrane bound antibody
has light and heavy chains
disulphide bridges
how are pathogens detected by t and b cells
secondary lymphoid tissues
MHC proteins display peptide antigens to T cells, allowing activation. (HLA other name) what is the difference in class 1 and 2
class 1 - expressed on all nucleated cells, present peptide antigens to cytotoxic T cells
class 2 - expressed only on dendritic cells, macrophages and b cells, present peptide antigens to helper T cells
which is the first immunoglobulin produced in an immune response
IgM
which immunoglobulin is produced in an allergic response
IgE
immunoglobulins have dual biological functions, what are these
recognition - binds to antigen mediated by variable region sites
effector - clearance mechanisms mediated interaction of constant region with effector molecules
purpose of IFN-gamma 2
activates macrophages induces MHC class II expression
which 3 proteins expressed in the acute phase prevent infection spread, and can also be diagnostic markers
C reactive protein (CRP)
Serum Amyloid Protein (SAP)
Complement proteins (C3,4,5 ect)
serum CRP which would indicate either an active inflammation or a bacterial infection
40-200mg/L
10-40 = mild inflammation, viral infection
other than a severe bacterial infection, >200mg/L serum CRP levels indicates
burns
t/f transendothelial migration can occur in both arterioles and venules
false
bp too high in arterioles
once endotheliall cells become activation during acute inflammation, what is expressed which allows the adhesion of immune cells
sellectins
ICAM
another name for neutrophils
polymorphonuclear cells (PMNs)
give 4 examples of opsonins
C3b
C-reactive protein
IgG
IgM
explain how dendritic cells initiate the adaptive immune response
inflammatory cytokines stimulate immature dendritic cells express co-stimulatory molecules
dendritic cells recognise and phagocytose pathogens (PRR-PAMP)
dendrites display small peptides of antigen on surface in complex with MHC
migrates to secondary lymphoid tissue, meeting t nd b
name of protein which presents peptide antigens to helper T cells
MHC Class II
T cell activation requires 2 signals, what are these
signal 1 - MHC class I
co-stimulatory molecule B7 (on dendrite) - CD28 (on T)
t/f B cells do not need dendrites to recognise antigens
true
do not need MHC to present antigen
most abundant antibody
IgG - actively transported across placenta
which antibodies are given by the mother to the child
IgG and dimeric IgA
other than the dual biological functions of antibodies (Recognition and effector) what other functions can they carry out 5
agglutination opsonisation stimulate NK cells trigger allergic responses undergo class switching (heavy chain switched = different antibody)
associated functions of IgM when in membrane-bound form/in plasma and secretory fluids as a pentamer
membrane - antigen receptor, activates B cells
plasma - agglutination, activates complement system
define agglutination
cross-linking of antigens producing clumps by an antibody
other than IgM, which antibody mediates agglutination
IgG
how does agglutination benefit the immune system
clumps all pathogens together, increases efficacy of phagocytosis
which antibody is dominant during secondary immune response
IgG
other than agglutination, name 5 other associated functions of IgG
complement system activation foetal immune protection neutralisation opsonisation NK cell activation
when in monomeric form, IgA activates B cell (as found in serum), what is its function when in dimeric form
neonatal defence
neutralisation (at mucosal sites)
is dimeric when present in secretory fluids (sIgA)
how do effector Th cells help T cell response
secretion of IL-2 - stimulates proliferation and differentiation of antigen-activated T cells (antigen-activated B cells too)
how are macrophages ability to kill pathogens improved
expression of co-stimulatory molecules (IFN-y) by effector Th1 cells
these hyper-activate macrophages
NK cells do the same thing
how do effector T- FH cells help B cells
effector T - FH cells re-activate in B cell zone in lymph and stimulate clonal proliferation of antigen stimulated B cells through co-stimulatory molecules
also secretes cytokines
how does cytotoxic T cells kill infected host cellls
recognises and binds, programs DNA fragmentation, inducing death by apoptosis
cytotoxic T cells released perforin, granzymes and granulysin, what does each do
perforin - forms pore
granzymes - activates apoptosis
granulysin - induces apoptosis
