Blood 2 Flashcards
how do neutrophils kill?
respiratory burst
what are the ROIs
suerpoxide anion, hydroxyl radical, hydrogen peroxide, hypochlorous acid
where does hypochlorus acid come from
from H2O2 by action of myeloperoxidase from azurophilic granules, produces hypochlorite (bleach)
what catalyzes the first step of the respiratory burst
NADPH oxidase
do phagosome membranes have NADPH oxidase
yes derived from plasma membrane
chronic granulomatous disease
involving any of the oxidase subunits
decreased or absent respiratory burst
recurrent bacterial and fungal infections
shorted life expectancy
specific granules contain
neutrophil
lysozyme: attacks cell walls of bacter, gram +
lactoferrin: competes with bacteria for iron and copper
collagenase: degrade ECM, easier access for neutrophil
azurophilic granules contain
neutrophil
myeloperoxidase: produces bleach
bactericidal/permeability-increasing protein (BPI): damages membranes of gram -
lysozyme
defensins: permeabilize bacterial membranes
neutrophil elastase: digest ECM
Chediak-Higashi syndrome
interferes with targeting of proteins to azurophilic granules, abnormally large vacuoles from fusion of azurophilic granules
don’t have mediators to kill bacteria
neutrophil extracellular traps (NETs)
strands of neutrophil chromatin with antimicrobial granule proteins
released from activated neutrophils
microbes stick and killed by high local concentrations of antimicrobial agents
help keep microbes from spreading
minimize local tissue damage
sepsis: NETs from within blood vessels
preeclampsia: form in intervillous spaces of placenta
require NADPH oxidase activity
how can neutrophils damage healthy tissue
elastase from azurophilic granules
collagenase from specific granules
release can occur during NET formation or phagocytosis
granules may fuse with phagosomes before it pinches off completely
what is pus and why is it green
dead neutrophils (necrotic death) green because of myeloperoxidase
how is pus removed
by macrophages
in what process are neutrophils important and what are 2 clinical indicators
important in acute inflammation
- leukocytosis: increased number, release of greater than normal numbers of neutrophils from bone marrow
- shift to the left: mature stores depleted, immature precursors released, shifts curve of nuetrophil age distribution
time course of an acute inflammation
- edema, leaky vessels by histamine
- neutrophils arrive during first wave, acute phase
- secrete chemotactic factors
- monocytes arrive, differentiate into macrophages, typical in late stage acute inflammation
- they phagocytize dead neutrophils, damaged tissue and other debris
extent of nuclear lobulation
neutrophil, eosinophil, basophil
neutro: 2-5 loves, thin strands
eosino: 2-3 lobes, thicker and/or shorter strands
baso: 2 poorly defined lobes
size and staining affinity of specific granules
neutro, eosino, baso
neutro: small, poorly staining
eosino: large, eosinophilic (pink to red)
baso: large basophilic (very dark purple)
specific granules of basophils
difficult to preserve, varied appearances
contents homogenous or grainy
may look like layers of membranes arranged in parallel stacks or whorls called myelin figures
basophil activation
involves IgE, made by plasma cells and binds to basophil receptors
primed but not activated
activated when exposed to antigen again and it binds to IgE causing it to cross-link
basophil activation leads to
- degranulation: mediators released are histamine and heparan sulfate, ECF and NCF
- cytokine synthesis and secretion: IL4 and IL3 promote class switching to IgE
- mediators from membrane phospholipids: LTC4 derived from arachidoic acid and PAF not from arachidonic acid
major effects of basophil mediators
- vasodilation and increased permeability: histamine, haparan sulfate, PAF and LTC4
- bronchoconstriction: LTC4, PAF, histamine
- increased mucus secretion: histamine, LTC4
- class switching: cytokins IL4 and IL3
- chemotaxis of eosinophils, neutrophils, monocytes and macrophages: ECF, NCF, PAF
- itch (pruritis): histamine
why is limited basophil activation beneficial?
- vascular permeability makes it easier to reach tissues
- increase mucus helps trap particulates
- mild bronchoconstriction increases velocity of airflow
why is excess basophil activation bad?
- edema due to leaky vessels
- excessive mucus secretion, nasal congestion
- excessive bronchoconstriction, restricts airflow
how can Type 1 hypersensitivity manifest
hay fever: nasal mucosa involved
asthma: bronchioles involved
hives (urticaria): skin involved
anaphylaxis: systemic rather than local, make unusually large amounts of IgE
eosinophils lifecycle
- IL5 stimulates their maturation
- circulate 8-12 hours
- leave vascular system by diapedesis, responding to histamine and eotaxins
- lifespan can vary from a few days to around 18
- greatest numbers in lamin propria of GI tract, except esophagus
- eosinophilia associated with: infection with parasitic worms, allergy, asthma, eosinophilic gastrointestinal disorders
eosinophils morphology
- nucleus heterochromatic and bilobed
- specific granules contain crystalloid embedded in amorphous matrix
- they can have shiny appearance by LM
- granules less eosinophilic at early stages
- EM crystalloid may be lighter or darker than surrounding matrix
eosinophil activation
- can be activated experimentally by different stimuli
- not clear what major in vivo activator is
- one is analogous to IgE-mediated activation of basophils
- eosinophil Fc receptors recognize IgG, IgA and secretory IgA
what do activated eosinophils do?
- secreted stored mediators from specific granules by: exocytosis (fuse individually with plasma membrane) or piecemeal degranulation (small vesicles bud off and fuse with plasma membrane, specific granules remain intact, different stimuli trigger secretion of different subsets)
- respiratory burst that produces: superoxide, hydrogen peroxide, hypochlorite, hypobromite
- synthesize and secrete lipid mediators (LTC4, PAF) from lipid bodies formed soon after activation
major eosinophilic functions
- kill larvae of certain parasitic worms, by secreting ROIs and mediators from specific granules: MBP (major component of crystalloid, reason for eosinophilia), ECP EDN, EPO (catalyzes formation of hypochlorite and hypobromite)
- phagocytize and destroy ag-ab complexes
- modulate basophil and mast cell activity: MBP activates them, can also destroy their mediators (arylsulfatase - LTC4, histaminase - histamine). Can have stimulatory or inhibitory effects
- antiviral activity against some ssRNA viruses via ECP and EDN RNAse activity
Asthma
eosinophils beneficial in parasitic infections and allergic reactions but can contribute to lung damage in chronic asthma -mast cells are major effector in early attack eosino involved in late phase -mediators can cause: damage to ciliated cells SM hypertrophy and hyperreactivity bronchoconstriction edema and leukocyte infiltration increased fibrosis
eosinos may also be involved in increased numbers of goblet cells (hyperplasia) and increased mucus production
monocyte morphology
- wide size range, includes largest
- irregularly shaped nuclues, not lobulated
- lacy chromatin
- nucleus and ctyo stain paler
- cytoplasm is abundant
- few azurophilic granules, no specific granules
- large, pale vacuoles
- well developed golgi, it produces azurophilic granules throughout monocyte lifespan
neutro have little golgi: cant produce azurophilic or specific granules, made only during differentiation
monocytes can differentiate into
macrophages
- they circulate in blood for a few days then enter tissues via diapedesis
- differentiate in extravascular tissues
- during inflammation rate of diapedesis increases greatly (make up wave of cells that arrives day after neutros at site of inflammation)
morphology of histocytes
-greater phagocytic activity than monocytes
-more phagosomes, secondary lysosomes, plasma membrane pseudopods, etc
-presence of phagocytized material in cyto
-usually larger than monocytes
more irregular nucleus
macrophage functions include
- phagocytosis: ordinary and removal of apoptotic cells, tissue debris, nuclei extruded from RBCs, old RBCs especially in spleen
- act as APCs: phagocytize and process antigen, partially degraded by lysosomal enzymes, bind to MHCII and presented to T helper cells
- secret products that promote:
- inflammation: cytokines, IL1, IL6, IL12
- hematopoiesis: CSF, GM-CSF
- wound healing: growth factors, TGF-alpha
- normal turnover of ECM: proteases such as elastase, collagenases - wall off large particles or microorganisms: chronic inflammations, unable to eliminate
- epithelioid cells: groups form resembling epithelium
- giant cell: fuse together, multinucleated
what is an important activator of macrophages
interferon gamma (IFN-gamma)
macrophage-related cell populations
osteoclasts in bone microglia in CNS aveolar macrophges (dust cells) in alveoli kupffer cells in liver langerhans cells in epidermis histiocytes in connective tissue
ostoeclasts and histiocytes are bone marrow depenedent
others derive from precursors from yolk sac and/or fetal liver, maintained in postnatal life by mitosis
small lymphocytes
> 90% of lymphocytes in blood
- inactive in immune responses
- nucleus kidney bean, highly heterochromatic
- tin rim of basophilic cytoplasm
- few azurophilic granules
- no specific granules by LM or EM
- few organelles by EM
large lymphocytes
- activated in an immune response
- more euchromatic
- smudged chromatic pattern
- cytoplasm increases
- also called immunoblasts or lymphoblasts
lymphocyte activation results in
- increase in size (blast transformation)
- repeated mitosis to form clone cells
- maturation of daughter cells into effector cells that carry out immune response or memory cells
what are the three functionally different types of lymphocytes
T cells, B cells, NK cells
- all arise from pluripotent hematopoietic stem cell in bone marrow
- T and B cells cant be distinguished
- NK cells have distinctive morphology
T cells
long life span 60-80% TCRs that recognize and bind antigen in specific manner essential for cell-mediated immunity killing virus-infected and tumor cells cannot be transferred passively
cytotoxic cells, helper T cells, regulator T cells, gamma/delta T cells
T cytotoxic cells
-CD8+ surface marker
main effector cells
can kill target cells
killing requires close contact
killing mechanisms include secreting mediators such as
-perforin: help granzymes gain entry into cell
-granzymes: serine proteases whose activities include apoptosis
T helper cells
CD4+ surface marker
recognize antigen on APCs such as macrophages, dendritic cell or B cell
secrete cytokines to help activate T cytotoxic cells and B cells
CD4 stabalizes interaction btw helper and APC
HIV infection
CD4_ cells are infected and killed
binding of viral envelope protein to CD4 is first step that allows virus to gain entry into a cell
regulatory T cells
down regulate immune resposnes
gamma/delta cells
within epithelial layers
can constitute majority of intraepithelial lymphocytes
first line of defense against antigens that penetrate epithelial barrier
B cells
humoral (antibody-mediated) immunity
can be transferred passively
plasma cells: effector cells derived from activated B cells
-secrete antibodies
-relatively short lived
-old plasma cells become russell body cells
large, distended RER cisternae, full of antibody and stain very eosinophilic
NK cells
large granular lymphocytes (LGLs)
have azurophilic granules with perforin and granzymes
do not carry CD4, CD8 or B cell markers
5-10%
killing virus-infected cells and tumor cells
are not specific for one individual antigen
receptors that recognize range of inhibitory and simulatory ligands
-balance determins if NK cell will become activated and lyse target cell
-down-regulating ligands on target cells that inhibit NK cells or up-regulating ligands that stimulate it
-kill by variety of mechanisms including perforin and granzymes
