Immunology Chapter 1 Flashcards
flora
community of microbes inhabiting a niche in the body
why do microbes infect humans?
to survive and replicate
commensal
aid in digestion
provide vitamins
prevent antibiotic resistance
pathogenic
opportunistic or not
4 kinds (bacteria, fungi, viruses and internal parasites)
constant interactions with hosts
endemic diseases
gradually changing, often not deadly
high mortality is only caused by
a new pathogen
antibiotic resistance
antibiotics kill commensal bacteria and allow pathogenic bacteria to gain a foothold
first line of defense
epithelial tissues
external: skin
internal: epithelia
epithelia
continuous with skin
very vulnerable tissues, covered by mucus
purpose of skin and mucosa
mechanical, chemical and microbiological barriers
protect internal tissues and organs
epithelial defenses
sebum in sebaceous glands
lysozyme acid in stomach
microbial flora
2 advantages of microorganisms
rapid reproduction
change characteristics much quicker and hosts
immune system
host cells dedicated to defense against microorganisms
distinguish between self and nonself
can mount an adaptive response
leukocytes
white blood cells
hematopoiesis
process of making hematopoietic cells (WBC and others)
progenitor cell of hematopoietic cells
pluripotent hematopoietic stem cell
pluripotent hematopoietic stem cell
capable of self renewal or maturation
located in yolk sac, fetal liver, spleen and bone marrow
hematopoiesis occurs all
through life because blood cells are short lived
3 hematopoietic lineages
lymphoid
myeloid
erythroid
erythroid cells
helps with clotting
erythrocytes and megakaryocytes
erythrocytes
RBC
carry oxygen
megakaryocytes
platelets
cells with giant nucleus
Myeloid
“of the bone marrow”
granulocytes, monocytes, macrophages, dendritic cells and mast cells
granulocytes
prominent granules, kill microorganisms in inflamed tissues
2-5 lobes in nuclei (polymorphonuclear leukocytes)
granulocytes from highest to lowest abundance
neutrophil > eosinophil > basophil
neutrophil
does not bind to basic or acid stain
pus
phagocytic
short lived
eosinophil
worm defense
bind acidic stain
basophil
parasite defense
very rare
bind basic stain
neutrophils are stored
and are released
in the bone marrow
on demand to fight infection
can neutrophils kill multiple bacteria sequentially?
NO!
can only kill 1
monocytes
circulate in the blood
single lobed nucleus
progenitors of macrophages
macrophages
resident in tissues
large, irregular shape
scavenge dead cells and debris, microorganisms
macrophages signal to
other cells via cytokines to respond to infections
dendritic cells
resident in tissues
star shaped
phagocytose and degrade pathogens
dendritic cells migrate from
tissues to lymphoid organs to begin adaptive response
mast cells
resident in connective and mucosal tissue
major role in inflammation
granules similar to basophil
Lymphoid
NK cells, ILC, B and T lymphocytes
NK cells
innate immunity
circulate in blood
prevent viral replication in infected cells
ILC (Inate Lymphoid Cells)
inane immunity
resides in tissues
secretes cytokines to help activate macrophage and granulocyte responses to infection
B and T lymphocytes
adaptive immune response
circulate as immature, inactive cells
powerful adaptive response of B and T cells occurs in
1-2 weeks
B and T cells recognize pathogens which drives
lymphocyte selection, growth and differentiation
B cells
produce antibodies (soluble form of B cell receptor)
cytotoxic T cells
CD8
kill cells infected with virus or bacteria
helper T cells
CD4
secrete cytokines to help activate other cells
B cell receptor
surface Ig
secreted form in antibody
binds pathogen amino acids, sugars, etc
T cell receptor
only surface bound
binds pathogen peptides
each cell has a receptor that
binds a unique target
abundance of leukocytes in human blood (from high to low)
neutrophils
lymphocytes
monocytes
eosinophils
basophils
primary lymphoid tissues
bone marrow and thymus
bone marrow
B and T cells originate here
develop and enter blood circulation
thymus
T cells develop and mature here
Secondary lymphoid tissues
all others except BM and thymus
battleground of lymphoid
secondary tissue
pathogens trapped here and activate lymphocytes
Lymphatic Vessels
Originate in capillary beds
Collect plasma leaking from blood vessels and extracellular fluid
Lymph Circulation
Blood Vessels –> Lymphatics –> Thoracic duct –> Left subclavian vein –> back to blood
How is lymph circulation driven? What happens in absence?
Driven by movement of body parts
Edema can occur in absence
Lymph Nodes
Secondary lymphoid tissues at intersections of LV
Unique property of B and T cells
Can move through blood and lymph
Movement of B and T cells
Primary lymph tissues –> blood –> secondary lymph tissues –> lymph –> return to blood
Activated Lymph Cell
Remains in lymph node for a while
Unactivated Lymph Cell
Leaves in efferent lymph –> blood
Lymphocyte Recirculation
allows for continual survey of secondary lymphoid organs for infection
What is the exception for lymphocyte recirculation?
Spleen
What happens at lymph node step 1
Pathogens + infected dendritic cells carried to nearest lymph node by afferent lymphatics
What happens at lymph node step 2
Battlefield: lymphocytes encounter pathogens and pathogen products
What happens at lymph node step 3
Swollen glands: proliferation of activated lymphocytes at draining lymph node
What happens at lymph node step 4
T cells activated by dendritic cells –> Help B cells become plasma cells
Where do B-cells “hangout”?
Follicles
Draining lymph nodes are meeting place for?
Pathogens
Dendritic cells carrying pathogen fragments
B and T cells
The spleen removes…
damaged or senescent RBCs
What does the spleen provide?
Adaptive immunity against pathogens IN BLOOD
Asplenia
No spleen
Patients susceptible to infection by encapsulated bacteria
GALT
Gut associated
Tonsils
not every MALT is a
GALT
Peyer’s patch
transport of pathogens by M cells (GALT)
adaptive immune response timeframe
over four days
every adaptive response depends on an
innate immune resposne
purpose of innate immune response
immediate defense, prevents spread
steps of innate immune response
- recognition of pathogen
- signaling
- recruitment of destructive effector mechanisms
overall effect of innate immune response
produce inflammation
complement helps
innate immune system recognize and destroy pathogens
inflammation includes
local dilation of blood vessels (redness/heat)
leakage of blood plasma into connective tissue (swelling)
pressure on nerve endings (pain)
benefit of inflammation
bring large numbers of cells and molecules rapidly to infected tissue
adaptive immune response
organized around ongoing infection
adapters to infecting pathogen
long lasting and highly specific
receptors of the adaptive immune system are
general type but highly specific
lymphocytes with receptors recognizing pathogens are selected to
survive, proliferate and differentiate
clonal selection and clonal expansion
selects for large numbers of effector lymphocytes specific for pathogen
adaptive immune response takes place in
secondary lymphoid tissues
dendritic cells are the
link between innate and adaptive response
dendritic cells are essential for
primary immune response
priming step in adaptive immune response
activate antigen specific T cells to divide and differentiate into effector T cells
MHC (major histocompatibility complex) molecules
complex of MHC with pathogen peptide is what T cell receptor recognizes
antigen presenting cell
two types of MHC molecules
MHC class I
MHC class II
MHC class I
intracellular pathogen
recognized by cytotoxic T cell (CD8)
MHC class II
extracellular pathogen
recognized by helper T cell (CD4)
Cytotoxic T cell response
kills cells infected with pathogen
intracellular
Helper T cell response
secrete cytokines to assist other types of cells
extracellular fluid and spaces
B cell regions
variable region - binds pathogen/toxin
constant region - binds effector cell/complement molecule
humoral immunity
immunity due to antibodies and their actions
antibodies circulate in blood stream
cell mediated immunity
direct cell to cell contact
post infection
stop immune response
reduce inflammation
repair damaged tissues
what lives after infection?
long lived clones of memory T and B cells persist
immunological memory
persistence of some cells from the AIR that provide long term protection
subsequent infections have
much stronger, faster response with less illness
purpose of vaccination
induce immunological memory to a pathogen so that future infection elicits strong, quick response
vaccine must induce
both innate and adaptive response
a new _______ response has to be made each time a pathogen _________
primary
changes
negative selection
removing or suppressing immune cells that can attack self
central tolerance
occurs in primary lymphoid organ
peripheral tolerance
occurs outside a primary lymphoid organ
regulatory T cells (CD4)
suppress T cell reactivity against normal tissues
misdirected adaptive immune responses
autoimmune disorders
allergy (hypersensitivity)
transplanted tissue
tissue incompatibilities caused by MHC polymorphisms in donor and recipient
recipient is immunosuppressed so that donor tissue can be accepted
