Unit 6 - Immune System Flashcards
3 major functions of immune system
- protect body
- remove dead/damaged tissues and cells
- recognize and remove abnormal cells
what are:
a) autoimmunity
b) allergies
c) immunodeficiency
a) incorrect responses
b) overactive responses
c) lack of response
what are pathogens?
disease-causing agents
bacteria characteristics
- cell surrounded by a cell membrane & usually a cell wall
- antibiotics
virus characteristics
- once inside host, what happens?
- what happens with new viral particles?
- intracellular pathogens
- not cells -> nucleic acid core with protein coat
- some have envelope derived from host cell membrane
- antivirals
- once inside host, virus nucleic acid takes over
- new viral particles can either rupture host cell or bud off from host cell
what are immune system organs called? why?
lymphoid organs because lymphocytes are found there
what are lymphoid organs connected by? what do they carry?
connected by blood vessels and lymph vessels
they carry lymph (clear fluid)
what is lymph? what does it do?
lymph is essentially ECF that has left capillaries & filter through tissue
it acts as a conduit for immunologically active cells to travel through
where are lymph nodes located?
strategic locations like:
- knee, groin, elbow, shoulder, neck
what are regions of the body outside lymphoid organs called?
periphery
primary lymphoid organs
- what happens here?
- what’s included?
- organs where lymphocytes develop
- bone marrow (all blood cells originate here)
B cells mature here - thymus; T cells mature here
(most active in childhood)
secondary lymphoid organs
- what happens here?
- what are the structures & functions (4)?
- organs where lymphocytes interact and initiate responses (spleen, lymph nodes, tonsils, and Gut Associated Lymphoid Tissue (GALT))
- filter blood and lymph -> for pathogens & pathogen-containing lymphocytes
- afferent lymph vessel brings in lymphocytes from periphery
- efferent lymph vessel allows them to keep circulating
- pulp inside lymph nodes allows mixing of lymphocytes and other leukocytes
- arteries & veins (nutrients & O2) plus non-lymphatic leukocytes
secondary lymphoid organs:
- spleen and lymph nodes _________
- tonsils and GALT _________
- surrounded by a fibrous wall -> encapsulated
- unencapsulated -> diffuse
WBCs are ____ & ____ than RBCs
bigger & less numerous
what are the 6 types of leukocytes?
neutrophils
lymphocytes
monocytes (macrophages)
eosinophils
basophils (mast cells)
dendritic cells
granulocytes
- prominent cytoplasmic granules
- eosinophils, basophils, neutrophils
phagocytes
- can engulf and ingest pathogens
- neutrophils, macrophages, dendritic cells
cytotoxic cells
- kill other cells, even self-cells
- eosinophils & some lymphocytes (NK, Tc)
antigen-presenting cells (APCs)
- display fragments of pathogens on cell surface
- some lymphocytes, dendritic cells, macrophages
eosinophils
cytotoxic granulocyte with bright pink staining granules
- defend against parasites & allergens
- not a lot in periphery, shortlived
- found in digestive tract, lungs, genital tract, skin
- respond by binding to an antibody-coated parasite and degranulate -> spew cytotoxic granule contents
- also degranulate in allergic responses
basophils
granulocytes involved in allergic responses
- have large dark blue staining granules
- in blood (rare), mast cells in tissue -> found in digestive tract, lungs, skin
- granules contain histamine, heparin, cytokines
- also degranulate in allergic responses
neutrophils
phagocytic granulocytes
- most abundant leukocyte
- live a few days, can eat a few bacteria
- can leave circulatory system to attack pathogens in tissues
- granules contain cytokines (fever, inflammation)
monocytes
precursor cells of tissue macrophages, uncommon in blood
- in blood for some hours -> move into tissue to be macrophages
- macrophages are large amoeboid cells, phagocytose old RBCs and dead neutrophils
- can eat a lot of bacteria
- in adaptive immune response (APCs - display antigens)
lymphocytes
very involved in acquired immunity
- around1/4 of leukocytes
- very little in circulation; most in secondary lymphoid tissues
- a LOT per individual
- they look the same microscopically but have different functions
dendritic cells
phagocytic APCs
- long thin process like neuron dendrites
- found in skin and other organs
- phagocytose pathogens, digest, present on surface
- “activated” cells then migrate to secondary lymphoid organs to present to lymphocytes
precursor to all blood cells?
pluripotent haematopoietic stem cells
types of lymphocytes (2)
B cells
T cells
B cells
- made and matured in bone marrow, NOT reason for name (chicken: Bursa, invagination of colon)
- make antibodies (on cell surface or free-floating)
T cells
- made in bone marrow, matured in thymus, IS reason for name
- use contact-dependent signalling via T-cell receptor on T cell membrane (can only bind to MHCs);
can NOT bind to free Ag
what does MHC stand for?
major histocompatibility complex
MHC I / MHC II
- on all nucleated cells
- on APCs
types of T cells and what MHCs they recognize?
cytotoxic T cells (Tc) or killer T cells
- class I MHC
- kills cell
helper T cells (Th)
- class II MHC
- promote differentiation of B cells and Tc cells, can activate macrophages
regulatory T cells (Treg)
- class II MHC
- suppress other immune cells to prevent excessive response
how does immune system use chemical signalling?
a. antibodies -> bind to antigens as signal
b. cytokines -> affect growth of activity of other cells
innate vs adaptive immunity
innate:
- more rapid, non-specific, can lead to adaptive
- inflammation is distinctive in innate
- all organisms have
adaptive
- specific, days to weeks
- memory
- divides into cell-mediated immunity & antibody-mediated immunity/humoral immunity
- only in vertebrates
innate:
how does second line of defence (circulating leukocytes & blood proteins) react?
provide clearance/containment of pathogens until adaptive response kicks in
innate:
what does first line of defence include?
physical barriers (skin, mucus lining of gut/genital tract, ciliated epithelium of respiratory system)
chemical barriers (stomach acid)
(most vulnerable; epithelium exposed & thin)
innate immune system cells
- majority phagocytes
- attract other cells by secreting cytokines
(chemotaxins - attract other immune cells)
a. cytokines & other immune blood proteins
b. tissue injury products
c. bacterial products
extravasion =?
phagocytes leave circulation and enter tissue through capillary walls
what happens if pathogen does not have surface features recognized by phagocytes?
process is called?
blood proteins bind to and coat pathogen to “tag”
- opsonization
once phagocyte ingests, particle is in a vesicle called?
these fuse with lysosomes to form?
phagosome
phagolysosome
what is pus?
dead phagocytes, tissue fluids, debris
natural killer cells
- innate, but most lymphocytes are in adaptive
- bring about apoptosis
- can attack tumour cells
produce important cytokines:
inferons alpha and beta -> induce antiviral state in nearby cells
inferon gamma -> activates macrophages & other immune cells
inferons used for
interfere with viral replication
what do chemical mediators do?
innate response
inflammation
- signal to attract cells and chemical agents
- increase capillary permeability, fever
- physical barrier produced to prevent pathogen spread
- promote tissue repair
caused by cytokines released by macrophages
what chemical mediates most of the chemical mediator effects?
local or systemic?
what are its functions(4)?
interleukin-1 (IL-1)
mainly local, can be systemic
- loosen capillary wall
- act on liver to produce damage control blood proteins
- fever
- stimulate cytokine production
complement proteins
innate or acquired?
characteristics/processes?
innate response
- over 25 blood proteins activated by sequential proteolysis
- some are opsonins, some are chemotaxins
- some form Membrane Attack Complex (MAC Attack) to make holes in pathogen membranes -> lyse from water/ion intake
other names for adaptive immunity?
acquired
specific
what are the lymphocytes involved in acquired immunity?
B cells (activated form = plasma cell)
T cells
NOT NK cells
T & B cells can expand ____
clonally
what happens after B and T cells recognize a pathogen?
expand clonally -> many effector cells
(effector cells attack pathogen, some become memory cells)
which lymphocyte controls antibody-mediated immunity?
antibody-mediated immunity AKA?
B cells!
humoral immunity
antibodies AKA?
immunoglobulins
name all immunoglobulins/antibodies classes in humans
functions for all
MADGE:
IgM - primary responses -> activate complement
IgA - in secretions -> neutralize pathogen before entry
IgD - on B cell surface with IgM -> function unknown
IgG - most of plasma Ab, secondary response -> activates complement, opsonize
IgE - allergies -> recognized by mast cells
antibody structure has __ light chains and __ heavy chains
2 & 2
antibody structure:
explain Fab & Fc
what connects them?
Fab - arms with antigen binding sites
Fc - stem determines Ab class
there is a hinge between Fab and Fc
Fab stands for?
Fc stands for?
fragment antigen binding
fragment crystallizable
name for what Ag-bind site recognizes on antigen/where they attach
epitope
antibodies are most effective against ___ pathogens
extracellular
are antibodies effective against macromolecules?
yes!
do antibodies damage pathogens themselves? if not, what?
no, they make pathogens more visible to immune defenses or activate defences
antibody functions (7)
- opsonize Ag’s for phagocytosis
- antigen/pathogen clumping
- neutralize bacterial toxins
- activate complement
- activate B cells
- activate Ab-dependent activity (e.g. NK & eosinophils)
- activate mast cells to degranulate
how do cells interact with antibodies?
- B cells have antibodies on surface as receptors
- other cells use Fc receptors that bind to Ab Fc
what lymphocyte mediates cell-mediated immunity?
T cells
what is the only way for T cells to do its job? (communication-wise)
need to be in contact directly with target cell
cell-mediated response:
- types of receptor protein
- which T cells and functions
- class I MHC
- cytotoxic T cells; kill cells that express the peptides
- release perforin to make pores in target cell
- release granzymes, enter through pores, apoptosis
- can also express Fas ligand to trigger apoptosis - class II MHC
- extracellular pathogens
- phagocytose pathogens -> present to T helper and T regulatory cells
- TH: secrete cytokines to activate immune cells
- Treg secrete cytokines to suppress immune cells
bacterial infection often results in ___ response
inflammatory;
(redness, swelling, tenderness)
bacteria response stages (6) (not steps, just list)
- complement activated by bacterial wall
a. chemotaxins
b. MAC
c. opsonize - haemostasis if blood vessel broken
- phagocytes (make cytokines) and activated lymphocytes (present antigens)
- TH produce cytokine -> activate B cells
- B cells clonally expand & become plasma cells to make lots of antibodies
a. opsonins
b. activate complement - end of response most lymphocytes die, some become memory cells
viral infection overview (short) innate and acquired:
- when virus is extracellular, phagocytes and Ab’s can help (opsonin, neutralize)
- both Tcell mediated and humoral immunity
stages of viral infection response (6)
- once intracellular, most immune cells and Ab’s cannot reach
- infected host cell makes IFN beta and macrophages make IFN alpha
- host cells make cytokines, macrophages activate NK & Tc cells
- Tc cells recognize MHC I, perforin & granzymes for apoptosis, also Fas ligand for apoptosis
- some viruses turn off MHC I; NK cells kill any with no MHC I
- end of response, most Tc cells die but some become memory cells
allergic response overview (types of allergic responses, what effect does it have)
- inflammatory immune response to non-pathogenic antigen
- sensitive (atopic) people
Types:
- immediate hypersensitivity (Ab mediated)
- delayed type hypersensitivity (DTH) (T cell & macrophage mediated)
allergic response stages (hypersensitivity response)
- sensitization phase:
- like primary response
- antigen ingested by APC -> activate TH cell
- TH cell activate B cell -> make IgE
- TH and B cells become memory cells - re-exposure:
- like secondary response (strong and rapid response)
- generally, IgE on mast cells detect allergen
- mast cells degranulate (make cytokine and histamines) -> inflammation
severity varies:
- localized -> rash or hay fever
- systemic -> anaphylactic shock (vasodilation, circulatory collapse, bronchoconstriction)
MHC proteins are also called? (transplant related)
Human Leukocyte Antigens (HLA)
if donor and recipient share _____, often successful transplant
Human Leukocyte Antigens (HLA), AKA MHC
2 possibilities of transplant (rejections)
- rejection of host by donor tissue (graft vs host)
- reject of donor tissue by host (host vs graft)
do RBCs have MHC proteins? why? how do they differentiate?
no, no nucleus (MHC I -> nucleated cells)
group of antigens that make up four blood types (A, B, O, AB)
what happens if wrong blood type with transfusion?
antibodies react, cells clump (agglutinate)
MAC attack -> cells lyse -> Hb released
free Hb causes acute renal failure (kidneys try to filter blood with large molecules)
