Blood/lymphatics Flashcards
Functions of blood
oxygen delivery via RBCs CO2 removal via RBCs/HCO3 distribute nutrients to the body distrbuution of hormones hemostasis (clotting) buffer body fluids/ osmotic balance regulation of body temp removal of metabolic waste immune cell circulation
plasma composition
see table
cellular blood components
red cells platelets white cells: neutrophils lymphocytes monocytes eosinophils basophils
normal red cell morphology
anucleate
biconcave shape - helps them fit through capillaries
central pallor (dent) should be less than 1/2 the diameter of the cell
red cell function
oxygen delivery to tissues
removal of CO2 from tissues
both of these processes are mediated by hemoglobin in RBCS
Hemoglobin structure
two alpha and two beta chains
hemoglobin cannot be made without iron
each chain has a heme group
myoglobin
stores oxygen in tissues
iron deficiency anemia
hemoglobin cannot be made without iron -
red cells with very little hemoglobin appear pale and small
patients feel tired and shortness of breath, possibly heart palpitations
treatment = provide them with iron
hereditary spherocytosis
red cells look like perfect spheres, slightly smaller than normal RBCs and no biconcave shape
occurs due to mutations in the cytoskeleton or on membrane surface
- this causes them to have reduced SA but same volume - causes splenic trapping
- oxygen goes down and pH changes = hemolysis by WBCs
patients are anemic and present with symptoms of iron deficiency
sickle cell anemia
red blood cells take on sickle shape
at the nucleation phase the process is reversible - this stage can also be prolonged
when explosive growth of polymers occurs - red cells cant fit through capillaries - stick to vessel walls - clog blood vessels = sickle cell crisis - dangerous and painful
what is a platelet
cytoplasmic fragments of cells called megakaryocytes
platelet structure
electron dense granules: mainly nucleotides (ADP) and Ca2+
specific alpha granules:
fibrinogen, factor V, vWF
platelet receptors
GP1bIX receptor - mediates attachment to vWF, leads to platelet activation
GPIIbIIIa receptor - mediates attachment to fibrin (final step in clotting) - seals the clot+activates the platelet
ADP receptors (P2Y12) - self activation mechanism
thrombin receptors (PAR1/2) -0 major part in coagulation cascade - also activation of platelet
thromboxane A2 receptor = activation
hemophilia
X linked recessive disorder hemophilia A = F8 deficiency hemophilia B = F9 deficiency clinically identical strong association between factor level and severity of disorder
hemophilia spectrum of disease
factor level is less than 1%:
severe disease, frequent spontaneous bleeding; joint deformity and crippling
factor level 1-5%:
moderate disease, post traumatic bleeding, occasional spontaneous bleeding
factor level 5-20%:
mild disease
post traumatic bleeding
neutrophils
polymorphonuclear neutrophil or segmented neutrophil
generally first to arrive to site of infection
primary function is phagocytosis of bacteria, fungi, and debris
kill ingested bacteria via oxygen dependent or independent methods
reactive oxygen and nitrogen intermediates that neutrophils use to kill bacteria
reactive oxygen intermediates:
superoxide anion-phagocyte NADPH oxidase
hyperchlorite anion - myeloperoxidase
reactive nitrogen intermediates:
nitric oxide - NO synthetase
chronic granulomatous disease (CGD)
caused by deficiency of phagocyte NADPH oxidase (cant make superoxide anions)
leads to dysfunctional killing of bacterial and fungal organisms by neutrophils
patients present with recurrent bacterial and fungal infections
leukocyte adhesion deficiency (LAD)
caused by deficiency of LFA-1 integrin
leads to inability of neutrophils to migrate from blood to tissues
most patients with LAD die before 1 year of life from bacterial infections
eosinophil function
anti-parasitic function - anti parasitic protein called eosinophil cationic protein (ECP)
involved in allergic reactions
have enzymes that can generate lysosomal and oxygen radicals
basophil function
support mast cell responses during inflammation
involved in allergic reactions
have histamines
make prostaglandins and leukotrienes
granulocytes
basophils
eosinophils
neutrophils
monocytes
migrate into tissues and differentiate into tissue macrophages
have horse shoe nucleus
monocyte/macrophage function
phagocytosis of microorganisms and then killing via oxygen independent or dependent
macs only:
- secrete cytokines and chemokines to recruit immune cells to site fo inflammation
- present antigen to CD4+ t cells via MHC 2
changes involved in monocyte differentiation into macrophages
increase in size
increased number+complexity of organelles
increased phagocytic activity
increased amount of hydrolytic enzymes
complement cascade
series of enzymatic reactions where inactive precursors are converted to their active forms
cascades can be activated by antibody-antigen complexes or microbial cell wall components
results in generation of:
- anaphylotoxins
- opsonin (C3b): facilitates phagocytosis of microbes
- membrane attack complex
how are host cells spared from the complement cascade?
host cell receptors inactivate complement activation/effector function
decay accelerating factor inhibits formation of C3 convertase
membrane inhibitor of reactive lysis (MIRL/CD59) inhibits MAC assembly
lymphocytes
T cells =70-80%
- CD4:CD8 = 2:1 ratio
B cells = 10-20%
NK cells = 5-10%
T cells
formed in bone marrow - mature in thymus
CD4+ helper T cells = generals of immune response, help activate or silent other immune cells
CD8+ cytotoxic t cells = kill virally infected cells
B cells
produced and mature in bone marrow
produce and secrete antibodies
NK cells
formed and mature in bone marrow
kill virally infected cells and cancer cells
lymphocyte function
circulate between blood and secondary lymphoid tissues to facilitate the encounter with specific antigen
when it encounters its specific antigen in the lymph node it undergoes clonal expansion
severe combined immunodeficiency (SCID)
genetic disorder where t and b cells are deficient or dysfunctional
- usually defect in RAG1/2 or IL-2y receptor subunit
usually die within first year of life
treatment = bone marrow transplant
bone marrow function
origin, maturation, development of all peripheral blood cells
classified as primary lymphoid tissue
blood cell formation is called hematopoiesis
sites of hematorpoiesis
fetus:
0-2 months = yolk sac
2-7 months = liver + spleen
5-9 months = bone marrow
infants:
bone marrow in practically all bones
adults:
vertebrae, ribs, sternum, skull, sacrum, pelvis, end of femurs
- progressive fatty replacement of bone marrow
components of the bone marrow
stem cells
bone marrow microenvironment
hematopoietic factors
stem cells
arise from yolk sac
self renewal
multi lineage differentiation potential
bone marrow microenvironment
extracellular matrix
stromal cells
notes have more details
hematopoietic growth factors
see notes
marrow sinusoids - egress of blood cells
blood vessels are lnes by endothelial cels but there are gaps
WBCs and RBCs can pass through
megakaryocytes - have protrusions that reach through the gaps - little buds break off of these and become platelets
bone marrow exam
extract bone barrow then take tissue chunk for biopsy
these are complementary to each other and therefore you need both to confirm the diagnosis
erythropoiesis
produces mature rbcs
cytoplasm changes from blue to orange due a decrease in NRA and increase in hemoglobin
nucleus becomes smaller as the chromatin becomes more compact - nucleus eventually expelled from cells - macs eat the nuclei
1 progenitor = 16 RBCs (circulate for 120 days)
control of erythropoiesis
kidney senses that O2 is low
the peritubular interstitial cells of outer cortex produce and secrete erythropoietin - promotes erythropoiesis = circulating red blood cells
patients with renal failure do not produce enough erythropoietin and become anemic -treatment = recombinant erythropoietin
thrombopoiesis
thrombopoietin is the major driving factor - made in the liver
megakaryocytes are large because they undergo nuclear divisions but not cytoplasmic divisions -make a lot of mRNA and package them into granules
platelets are small plasma cells with granules inside of them
thrombocytopenia in liver failure
liver produces thrombopoietin
patients with liver failure often have decreased platelet count (thrombocytopenia) and are at risk for bleeding
granulopoiesis
negative feedback inhibition by mature forms
segmented nucleus indicates maturation
eosinophil and basophil maturation are similar
key factor = G-CSF
monocytopoiesis
same progenitor cell as for segmented neutrophil
key factor = M-CSF
acute myeloid leukemia
mutations that preserve the self renewing properties of stem cells by interfere with maturation lead to continuous proliferation of immature daughter cells
these cells eventually take over the bone marrow and lead to acute myeloid leukemia
see notes for mechanism
lymphopoiesis
T cells, B cells, NK cells arise from the same stem cell
stages of maturation defined by surface antigen expression
antibody (immunoglobulin) structure
antibodies have 4 polypeptide chains: 2 heavy and 2 light
each b cell produces antibodies with a single specificity that is different from those produced by other b cells
immunoglobulin heavy chain rearrangement (VDJ)
RAG-1 and RAG-2 are involved
similar gene rearrangement occurs within the light chain gene
produces 10^10 antibody repertoire
outcomes of b cell maturation
see notes
Burkitts lymphoma
b cell lymphoma
grows rapidly
cells appear large and nuclear chromatin are open
stary sky pattern bc macs are trying to phagocytose dying malignant cells
caused by:
- C-myc is an oncogene normally on chromosome 8
- the gene is rearranged and placed on chromosome 14 in front of b cell heavy chain promoter - therefore starts making a bunch of the c-myc gene causing uncontrolled cell proliferation
folicular lymphoma
b cell lymphoma
usually in older patients
uncontrolled growth in lymph nodes
caused by:
- translocation involving BCL-2 which is a tumor surpressor gene
- bcl-2 gets translocated to promoter , doesn’t let cells die because it stops apoptosis
cellular composition of the thymus
thymocytes (immature t cells) dendritic cells macrophages cortical epithelial epithelio-reticular cells
thymocytes
immature t cell precursors
migrate to thymus from bone marrow using CD44 and alpha integrin 4 homing
rearrange TCR genes in the thymus
selected to die via apoptosis or mature into T cells based on TCR specificity
t cell maturation/development
see notes
cortical epithelial cells
interact with double positive thymocytes in the cortex to mediate positive selection
dendritic cells
located in thymic medulla
interact with single positive thymocytes and mediate negative selection
epithelio-reticular cells
form a continuous cellular layer that lines the capsule and around the blood vessels called the blood-thymus layer
barrier prevents exposrue of te immature thymocytes to blood borne antigens
Hassall’s Corpuscles
appear early in life and are of unknown function
made of epithelial cells that had undergone degeneration and organize themselves into concentric eosinophilic whorls of material called thymic corpuscles
self tolerance: regulatory t cell model
t regs prevent autoimmunity
immune suppressors
thymic involution
as we age functional parenchyma of the thymus is replaced with fat and connective tissue - organ diminishes in size
thymus is not nonfunctional:
- with age, more lymphocytes get trained, don’t need as many new ones (still need some)
- parenchyma never completely disappears - retains some function
primary and secondary lymphoid tissues
primary:
bone marrow
thymus
secondary: spleen lymph nodes tonsils, adenoids payers patches
circulatory/lymphatic system interaction
at the capillary beds - interstitial fluids + cells/cell products/pathogens/debris enter lymphatic capillaries
afferent lymph vessel carries lymph fluid to lymph node (acts as a filter)
filtered lymph exits node via efferent vessels
drains into the thoracic and returned to the heart
lymphatic vessels
have valves to make sure fluid flow is unidirectional
afferent vessels bring lymph to the lymph node
efferent vessels take lymph fluid away from node via thoracic duct and back in circulation
blind-ended lymphatic capillaries
lined by endothelial cells - the gaps are where the interstitial fluid will get through into the lymph vessels
tissue fluid management depends on:
capillary hydrostatic pressure capillary permeability effective oncotic pressure (difference between plasma and interstitium) lymphatic drainage tissue tension
lymphedema
net accumulation of interstitial fluid due to impaired lymph drainage
blockage or damage of lymphatic vessels - causes impaired lymphatic drainage
secondary lowering of colloid osmotic pressure differential due to reduced removal of protein from interstitium
examples: radiation treatment, post-mastectomy, filariasis
contents of afferent lymphatic vessel
contains DCs carying antigen, particulate antigen, few lymphocytes
function of lymph nodes
generation of t and cell immune responses
location where lymphocytes can interact with APCs and particulate antigen
particulate matter and microorganisms that enter lymph are phagocytosed to prevent them from entering blood
allows for lymphocyte activation and is a barrier for blood infections
lymph node structure
capsule sinuses afferent and efferent lymphatics blood vessels parenchyma: cortex, paracortex, medulla
lymphocyte compartments in lymph node
cortex:
- primary follicles - naïve b cells
- secondary follicles - activated b cells in germinal centres
paracortex:
- t cell areas
medulla:
- plasma cells secreting antibody
- few activated/memory t cells and b cells transiting into efferent lymph
high endothelial venules (HEV)
specialized post capillary venous swellings characterized by plump endothelial cells
allow lymphocytes that are circulating in the blood to directly enter a lymph node (crossing HEV)
follicular dendritic cell (FDC)
located in the germinal centers of primary and secondary follicles
present antigen to b cells but do not digest and present on MHC
- instead they bind particulate in antigens and present that to the b cells
medulla of lymph node
medullary cords contain plasma cells which secrete antibodies into medullary sinuses
medullary sinuses empty into efferent vessels
- sinuses contain macrophages which phagocytose particulate matter/microorganisms, preventing their entry to blood
T and B cell activation in the lymph node
DCs from afferent vessel meet with lymphocytes from HEV (paracrotex)
migrate back to cortex and start to proliferate - some will access medullary sinus and become blood borne
what does the efferent lymphatic vessel carry?
antibodies from plasma cells
activated/memory t and b cells into thoracic duct - empties into venous circulation
facilitates distribution of antibodies and effector cells throughout the body
function of spleen white pulp
generation of t and b cell responses (antibodies) against blood borne pathogens
main protection against streptococcus pneumoniae and niseria menigitidis
function of spleen red pulp
macrophages in splenic cords phagocytose blood borne pathogens
grooming of RBCs and phagocytosis of old ones - gets rid of RBCs with defects
splenic sinusoids
removes damaged or aged RBCs from circulation
also allows the migration of leukocytes from the cords into the circulation
they are lined with DCs so if pathogens or antigens pass through they will be phagocytosed
post splenectomy
patients are susceptible to blood borne infections:
meinigitis and pneumonia
these infections would be fatal in asplenic patients
patients must be immunized against these and treated quickly if infected
red cell grooming is absent therefore red cells contain characteristic inclusions:
- howell jolly bodies (sm. nuclear remnants)
- pappenherimer bodies are abnormal granules of iron
ABO blood antigen system
ABO antigens= carb antigens expressed on surface of RBCs, platelets, endothelial cells
inherit one allele from each parent
co-dominant expression
four possible phenotypes: A,B,AB,O
genetic basis of ABO blood antigen system
fucosyl transferase 1 (FUT1) gene: makes the O or H antigen backbone (chromosome 19)
Glycosyltransferase A (GTA or A gene): adds N-acetylgalactosamine, A antigen (chromosome 9)
glocosyltransferase B (GTB, B gene): adds galactose (B antigen) (chromosome 9)
O blood group is due to lack of GTA an GTB
hyperacute rejection mechanism
see notes
acute hemolytic transfusion reaction
see notes
Rh blood group system
glycoprotein antigens expressed on red cells
coding genes on chromosome 1
RHD gene: RHD protein present = D antigen, lacking = d
Rh+ = D Rh- = d
hemolytic disease of the newborn
result of incompatibility between maternal and fetal blood antigens (most common with RhD incompatibility)
mother is Rh- and fetus is Rh+
fetal Rh+ RBCs cross placenta and enter maternal circulation from:
- miscarriage
- bleeding
- delivery
mother then develops anti-Rh antibody
antibody crosses placenta and results in hemolysis in fetus
first born is usually not affected bc antibody formation takes time
consequences for fetus: develops anemia death due to heart failure jaundice/anemia (cant clear bilirubin) seizures and brain damage (high bilibrubin)
how to prevent hemolytic disease of the newborn
all mothers are tested for Rh early in pregnancy
if mom is Rh -:
- rhig/rhogam (anti-RhD immunoglobulin) is given at 28 weeks of gestation - at the time of delivery and any trauma or significant bleeding
- this antibodies masks D antigen on fetal red cells and prevents maternal sensitization
treatment of hemolytic disease of the newborn
fetal blood transfusion through umbilical vein
group O, Rh- donor red cells are given
indications for transfusion
RBCs:
- anemia ( hemoglobin is 70-80 when it should be 120-170)
Platelets:
- thrombocytopenia (normal 150-450x10^9)
Plasma:
- acute bleeding due to trauma or surgery)
- warfarin therapy related intracranial hemorrhage
- patient on warfarin needing urgent surgery
complications of transfusion
see notes
ensuring safety in blood supply
health screen: questionnaire, interview + physical exam
diversion pouch (rid of skin pathogens)
universal leukoreduction
testing
selective donor use
investigation of transfusion reactions
donors notify of changes in their health
donor testing
ABORh: fwd and rev
matched blood transfused
clinically significant blood group antigens in select cases
infectious disease
most common bad reactions to blood transfusions
febrile non-hemolytic reaction
minor allergic
TACO
transfusion complications with highest mortality
TRALI is the most fatal but less common
TACO causes most deaths bc it is more common and is deadly
compatibility for platelet transfusion
try to match with the abo blood type because could have a hemolytic reaction due to antibodies in donor plasma or could have donor platelet destruction
compatibility for RBC transfusion
notes
compatibility for plasma transfusion
notes
ABORh typing: forward vs reverse typing
Forward: have three tubes: one with anti-A, one with anti-B and one with anti-D
put patients red cells into the tube and centrifuge-positive =cells stay higher in tube
reverse: have two tubes: one with cells that a antigen and the other has cells with b antigen
- add patient serum to determine if they have antibodies for that antigen
screen - indirect antiglobulin test (IAT)
goal: to see if the patient has antibodies against the antigens on the allogenic (donor) red blood cells
method:
screening red cells will be selected to have all clincially significant antigens on them
if a we get a positive reaction then we must determine the specific antigen
antibody identification (following positive screen)
similar method to IAT but have a panel with more cells
potential targets are ruled in or out based on reactivity with panel
crossmatch IAT
final check for compatibility
- ABO is checked and antibody reactivity against antigens not represented in the screen cells
method:
IAT method is performed with donor red cells instead of screening cells + patient serum
- positive reaction = pellet stays higher up in tube and does not migrate
electronic cross match
computer tells us if a red cell unit is compatible with the patient
this is done instead of phsyical cross match if:
- patient has no history of positive screen
-patient has no history of an antibody
patients ABO blood type is unknown
delayed hemolytic transfusion reactions
primary antibody response to a red cell alloantigen on recently transfused RBC
secondary antibody response to a blood group antigen that was previously encountered during pregnancy or transfusion
most commonly against RHD
usually extravascular hemolysis
- RBCs are opsonized and then phagocytosed in spleen by macs
milder presentation of anemia, low grade fever
direct antiglobulin test (DAT)
check for antibody bound to red cells in a patient
use a poly-specific anti-human globulin reagent ( can have specific ones is initial test is positive)
do this to investigate anemia and hemolysis
types of transplantation
solid organ transplantation
tissue transplantation
hematopioetic stem cells transplantation
types of grafts
homograft - genetically identical twins (no rejection)
allograft - within same species but not genetically identical (susceptible to rejection)
xenograft - between species (very susceptible to rejection)
types of donors
deceased donors: any solid organ or tissue can be taken
living donors: liver and kidneys
types of graft rejection
hyperacute- minutes to hours (caused by preformed antibody)
acute - days to months (preformed antibody is the cause but immunosuppression should stop this)
chronic - years ( not sure why this happens)
what causes hyperacute rejectoin
pre-existing antibodies to:
ABO blood group antigens on endothelium (mainly IgM)
HLA antigens: usually IgG against MHC1
- acquired through previous alloimmunizaton (transfusions, transplants, pregnancy)
MHC in humans
human leukocyte antigen =HLA
class 1 = A, B, C class 2 = DR, DQ, DP class 3 = complement proteins, TNF, heat shock proteins
polymorphism:
500 genes that most of us have
can’t match outside of ethnic groups
inherited on chromosomes - get a copy from mom and dad
HLA inheritance
follows typical medelian inheritance
1/4 chance that a sibling will be identical to you and a 50% chance that they would share half of the HLA genes, 1/4 chance of no match
HLA class 1 and 2 antigens
class 1:
monomer (alpha subunits) associated non-covalently with B2 microglobulin subunit
presents antigenic peptides to CD8+ t cells
expressed by all nucleated cels including endothelium
class2:
heterodimer
presents antigen peptides to CD4+ t cells
restricted expression to APCs or can be induced on endothelium/epithelium
functional relevance of HLA
required to initiate t cell mediated immune responses against pathogens:
- polygenic = survival advantage to individual
- polymorphic = survival advantage to species
transplantations- causes sensitization and can lead to transplant rejections
direct allorecognition
self T cell recognizes HLA of donor presenting on graft that is presenting donor self antigen
this results in transplant reactions which are more robust compared to pathogen detection
lymphocyte crossmatch
complement dependent cytotoxicity (CDC) cross match
flow cytometry crossmatch (more sensitive)
both are ways to avoid/minimize HLA antibody mediated rejection
virtual crossmatch
HLA typing/HLA antibody ID
similar to blood banking
typing for HLA-A,B,C,DRB,DQB,DQA,DPB
Methods:
serological
molecular techniques (sequence specific priming, sequence specific oligonucleotide probe)
HLA ID by luminex (solid phase) assay
latex bead coated with recombinant HLA
each bead has slightly different fluorescence emission
tells you exactly what the patient has
acute rejection
types: cellular, antibody mediated, mixed
dependent on t cell stimulation and co-stimulation
first step in allorecognition/activation
second step is effector mechanisms
How to minimize acute rejection
immunosuppressive agents:
- T cell depleting agents
- calcinerurin inhibitors
- MTOR inhibitors
- anti-proliferatives
- corticosteroids
typical immunosuppressive therapy for rejection prophlyaxis
induction with basiliximab (IL-2 receptor antagonist), if high risk induction with t cell depleting agents, mainly ATG
FK506 (or cyclosporin A for low risk patients)
mycophenolate mofetil (MMF) or myfortic - may switch to rapamycin if rejection occurs
predenisone - taper over time
treatment of acute cellular rejection
steroids
switch immunosuppressives:
cyclosporin to FK506
MMF/myfortic to rapamycin
ATG
acute antibody mediated rejection
difficult to treat
treatment options:
- plasmapheresis
- intravenous immunoglobulin (IVIG)
- rituximab - anti-CD20 mAB that depletes B cells but no activity against plasma cells)
- bortezomib: proteozome inhibitor with activity against plasma cells (still experimental)
problems with immunosuppression
opportunistic infection
increased risk of neoplasm
nephrotoxicity
tacrolimus - increased incidence of diabetes
