Immuno/Hemolymp Flashcards
Azathioprine MOA
Purine antagonist (thiopurine analog)
inhibits RNA/DNA synthesis
T lymphocyte specific
Converted to 6-mercaptopurine (active form)
Corticosteroids MOA
Impair Fc-mediated phagocytosis
Inhibit antibody production
Reduce complement fixation
Induce T cell apoptosis
IVIG MOA
Blocks Fc receptors (reduce phagocytosis)
Eliminate pathogenic autoantibodies
Inhibit complement activation (blocks C3 and C4)
Interfere with B and T cell activation
Modulates cytokine synthesis
Fas - Fas ligand blockade
Cyclosporine MOA
Calcineurin inhibitor (inhibits T cell activation) Decreases cytokine production (IL-2 important for T cell proliferation)
Mycophenolate MOA
inhibits Inosine Monophosphate dehydrogenase
-inhibits purine synthesis
-T/B lymphocytes depend on de novo pathway
May induce apoptosis in activated T-cells
Impair dendritic cell maturation
Melatonin MOA
stimulate platelet generation (promotes megakaryocyte fragmentation)
inhibit inflammatory response
Leflunomide MOA
Inhibits dihydro-orotate dehydrogenase -pyrimidine synthesis inhibitor decrease DNA/RNA synthesis Inhibits T cell proliferation inhibits B cell antibody production
Vincristine MOA
Accelerated fragmentation of megakaryocytes
-inhibits assembly of microtubules (binds tubulin)
Impairs platelet destruction by macrophages
-inhibits assembly of microtubules
Cyclophosphamide MOA
alkylating agent
disrupts DNA replication
Danazol MOA
interfere with antibody production
interfere with complement and antibody binding
Rituximab MOA
human anti-CD20 B-cell antibody
(CD20 needed for activation, differentiation, growth)
Depletes B cells via complement cytotoxicity
Etanercept MOA
inhibits TNFa (decoy receptor: soluble recombinant TNFa receptor Fc)
Three primary mechanisms leading to anemia?
Blood loss, hemolysis, reduced erythropoesis
T/F: Hemophilia A & B, two serious coagulopathies, affect only males?
True
Examples of infectious agents leading to anemia in dogs and cats?
Dogs: Babesia, Ehrlichia, Anaplasma, Leishmania, Leptospira, Mycoplasma
Cats: FeLV/FIV, FIP, Mycoplasma, Cytauxzoon felis
T/F: Icterus will develop with serum bilirubin concentrations >1.5 mg/dl?
False- greater than 2 mg/dl
T/F: Pigmenturia is noted later in the disease process and only with severe hemolysis?
False- it tends to occur earlier in the disease process of hemolysis and can occur even when mild
Why is cyanosis not a clinical sign of anemia even when hypoxemia is present?
Cynosis can only occur with methemoglobinemia >20% associated with oxidative injury to RBCs (acetaminophen or onion toxicity); there must be at leats 5 g/dl of unoxygenated Hb in the capillaries for cyanosis to be appreciated clinically
List and describe (5) compensatory mechanisms that result in the typical signs of anemia
- Immediate shunting of blood away from tissues with low O2 demand (skin) and toward vital organs. Occurs by selective peripheral vasoconstriction and splenic contraction in dogs
- Cardiac output- increase in HR and contractility initially that increases supply of O2 blood to hypoxic tissues; this may cause a mild systolic flow murmur
- Oxygen delivery enhancement- reduction in Hb-O2 affinity caused by increased metabolic acidity (Bohr effect) and increase in 2,3-DPG in dog RBC
- Decreased activity levels, exercise intolerance, etc especially in acutely anemic animals
- Erythropoetin-mediated accelerated erythropoiesis; this takes 5-7 days
What makes cats more susceptible to formation of heinz bodies?
Feline spleens have a structural variation that results in impaired ability to remove oxidized red blood cells.
Feline hemoglobin also contains more SH groups that are available for oxidation.
Number of reticulocytes that indicates a nonregenerative anemia vs regenerative anemia?
Non-regenerative: 100,000/microliter
Why are nRBC not a good indicator of regeneration in small animals?
They are seen in diseases without anemia or regenerative bone marrow response, such as with lead poisoning, sepsis, heat stroke, neoplasia, HAC
Severe hypochromasia is nearly diagnostic for what type of anemia
Chronic blood loss
List three innate mechanisms of RBC to protect themselves from oxidative damage
Superoxide dismutase, catalase, glutathione peroxidase, glutathione, metHb reductase
How do Heinz bodies form?
Heinz bodies are aggregates of denatured, precipitated hemoglobin within erythrocytes. They form as oxidation of the SH groups of hemoglobin results in conformational changes in the globin chains resulting in precipitation of globin. Aggregates of the denatured globin and metabolized metHb clump together
True or false: Formation of metHb is necessary for the development of heinz bodies
True
What makes cats more susceptible to formation of heinz bodies?
Feline spleens have a structural variation that results in impaired ability to remove oxidized red blood cells. Feline hemoglobin also contains more SH groups that are available for oxidation.
At what degree of methemoglobinemia will clinical signs develop? And what are common clinical signs seen with metHb?
20%
Clinical signs: chocolate colored mucous membranes, tachycardia, tachypnea, dyspnea, lethargy, anorexia, vomiting, weakness, ataxia, stupor, hypothermia, ptyalism, convulsions.
Cats can also develop facial edema
Coma and death may occur is metHb levels reach 80%
How is acetaminophen metabolized in the liver?
3 pathways
- Conjugated to sulfate compound by a phenol sulfotransferase
- Conjugated to a glucuronide compound by a uridine diphosphate-glucuronosyl transferase
- Can be transformed and oxidized by the cytochrome P-450 system that converts it to the reactive intermediate N-acetyl-P-benzoquinone-imine (NAPQI)
How many ml of blood is recommended for “trash blood” when taking a PCV from an indwelling catheter?
> 6 ml
Number of reticulocytes that indicates a nonregenerative anemia vs regenerative anemia?
Non-regenerative: 100,000/microliter
Why are nRBC not a good indicator of regeneration in small animals?
They are seen in diseases without anemia or regenerative bone marrow response, such as with lead poisoning, sepsis, heat stroke, neoplasia, HAC
Severe hypochromasia is nearly diagnostic for what type of anemia
Chronic blood loss
How are the metabolites of acetaminophen NAPQI and para-aminophenol (PAP) removed from the body?
NAPQI: reacts with GSH to form a nonreactive molecule (mercapturic acid) which is excreted in the urine
PAP: removed by biotransformation through N-acetylation with N-acetyltransferase (NAT), conjugation with GSH, or sulfation
Why are cats more sensitive to acetaminophen than dogs?
Cats have a limited ability to conjugate glucuronide as they lack a specific form of glucuronyl transferase that is needed to conjugate acetaminophen
They also have somewhat limited sulfate binding capacity
How do the metabolites of acetaminophen NAPQI and PAP result in toxicity?
NAPQI: oxidized hepatic proteins resulting in hepatocellular damage
PAP: co-oxidizes with oxyhemoglobin forming metHb and an oxidized PAP intermediate. The intermediate is reduced by GSH and the metHb is reduced by metHb reductase. When the metHb reductase, NADH, and GSH become depleted in erythrocytes, metHb becomes overt.
After metHb is produced, heinz bodies begin to form and aggregate into larger structures ultimately resulting in hemolysis
True of false: Unlike most substances that cause metHb, nitrites and nitrates are not documented to cause heinz body anemia
True
T/F: A sample that is agglutinating on a slide (before saline) confirms IMHA
False- you must put a drop of saline on the slide; if it is no longer agglutinating, roleaux may be present. If it is unclear, may need Coomb’s test to be sure (washes RBC)
Other differentials besides IMHA that can cause hemolytic anemias?
- Chemical-induced or oxidative-induced (drugs, copper, zinc, onions, hypophosphatemia)
- Hereditary erythrocyte defects (phosphofructokinase deficiency, pyruvate kinase deficiency)
- Infectious anemias (Babesia, Ehrlichia, Mycoplasma etc)
- Neoplasia (hemangiosarcoma, histiocytosis)
What other diagnostics besides PCV/TS and blood smear evaluation can/should be performed in an anemic animal?
Fecal, PT, PTT, Coomb’s test, CBC with reticulocyte count, bone marrow aspirate
+/- BMBT, vWF ELISA
Treatment for dogs with vWF disease?
Desmopressin at 1-4 mcg/kg SQ q3-4 hours
T/F: It is only necessary to transfuse anemic animals to 20-25% PCV and 20% of normal coagulation factors to maintain adequate O2 content and hemostasis?
True- not necessary to get PCV and coagulation parameters back to normal
Other differentials besides IMHA that can cause hemolytic anemias?
- Chemical-induced or oxidative-induced (drugs, copper, zinc, onions, hypophosphatemia)
- Hereditary erythrocyte defects (phosphofructokinase deficiency, pyruvate kinase deficiency)
- Infectious anemias (Babesia, Ehrlichia, Mycoplasma etc)
- Neoplasia (hemangiosarcoma, histiocytosis)
What breeds of dogs have been documented to have metHb reductase deficiency?
Chihuahua, Borzoi, English Setter, Cockapoo, Poodle, Corgi, Pomeranian, American Eskimo dogs
At what degree of methemoglobinemia will clinical signs develop? And what are common clinical signs seen with metHb?
20%
Clinical signs: tachycardia, tachypnea, dyspnea, lethargy, anorexia, vomiting, weakness, ataxia, stupor, hypothermia, ptyalism, convulsions.
Cats can also develop facial edema
Coma and death may occur is metHb levels reach 80%
Name 3 ways to determine the presence of methemoglobinemia
- Comparing a drop of venous blood to the patients blood on a white piece of paper
- Measurement with a co-oximeter
- Observe blood in an EDTA tube - it should remain dark
MOA of N-acetylcysteine for acetaminophen toxicity
NAC augments the endogenous glutathione stores as it is hydrolyzed to cysteine.
It also acts directly with NAPQI to form a nontoxic conjugate and increases the fraction of acetaminophen excreted as the sulfate conjugate.
The half life of acetaminophen is halved in cats that have been treated with NAC.
what is the most abundant type of leukocyte in dogs and cats?
neutrophils
what is the process of recognition of invading pathogens by neutrophils?
PRRs (pattern recognition receptors) on neutrophil membrane bind pathogen-associated molecular patterns (PAMPS) on the cell wall of pathogens. Binding of PRRs activates the neutrophils. Neutrophils also become activated when PRRs bind damage associated molecular patterns (DAMPS)
what are the 2 main mechanisms of neutrophils killing invading pathogens?
phagocytosis + degranulation
formation of neutrophil extracellular traps
The stimulus for production of neutrophils and homeostasis is not completely understood, but what is the one cytokine that we know plays a role?
granulocyte-colony stimulating factor
Where is G-CSF produced?
bone marrow stromal cells
in what types of tissue can G-CSF be secreted?
macrophages, monocytes, endothelial cells, fibroblasts
what cytokine causes stimulus of G-CSF release by bone marrow stromal cells?
IL-17
When neutrophils are at the end of their life span, what happens to them?
they undergo apoptosis and are phagocytized by IL-23 producing tissue macrophages
what does the term emergency myelopoiesis mean and what drives it?
ramping up of leukocyte production that occurs outside of a more steady-state production of neutrophils; it is driven by cytokine stimulation and PAMP/DAMP binding to PRRs on hematopoietic stem cells
where are neutrophils produced?
progenitor cells in bone marrow
in what parts of the body are neutrophils present?
bone marrow, blood vessels, microcirculation, tissues
The bone marrow normally has a large reserve pool of mature neutrophils. What does NOT stimulate release of these neutrophils? a-GCSF b-TNF beta c- IL-8 d- TNF alpha
C-IL8
what are the 2 pools where neutrophils can be located after entering circulation?
marginated- roll slowly along endothelium of smaller vessels and tend to stay in postcappilary venules
circulating- travel rapidly thru center of larger vessels
what percentage of neutrophils are in the circulating vs marginated pools in dogs? In cats?
dogs- 50/50
cats- 25/75 (circulating/marginated)
list the 3 main mechanisms of neutropenia
increased utilization
decreased egress from bone marrow
immune-mediated destruction
how does sepsis affect the neutrophil count
it precludes the hemoatopoietic system and progenitor cells from differentiating into committed myeloid progenitor cells
what are 5 specific causes (categories) of decreased neutrophil count secondary to decreased bone marrow release
- depletion of granulocyte progenitor cells
- medications/toxicants/radiation
- myelophthisis
- cyclic hematopoiesis
- ineffective granulopoiesis despite normal to excessive progenitor cells
what infectious diseases have been associated with neutropenia
parvo, rickettsial (E canis), felv, fiv
what is the suspected mechanism for estrogen toxicity?
a myelopoiesis inhibitory factor is produced by thymic stromal cells
what is the suspected mechanism for neutropenia in felv?
myelophthisis and myelodysplastic syndrome secondary to round cell neoplasia infiltrating the bone marrow
what is the mechanism of neutropenia in fiv?
infected bone marrow stromal cells secrete myelosuppressing factors that depress granulopoiesis; also myelodysplasia from infection of bone marrow
drugs assoc with neutropenia?
antiinfective agents, antiepileptics, colchicine, captopril, methimazole, phenylbutazone, chemo drugs
3 possible MOA of neutropenia resulting from certain drugs?
bone marrow necrosis or fibrosis
suppression of ranulopoiesis
immune-mediated destruction
What is myelophthisis?
failure of bone marrow to continue normal hematopoiesis b/c its decimation by infiltrating abnormal tissue (usually either neoplastic cells or collagen/myelofibrosis), rarely diffuse intramedullary inflammatin or osteoid
types of neoplasia most commonly assoc with myelophthisis?
round cell tumors- lymphoma, leukemia, multiple myeloma, histiocytic sarcoma
what is canine cyclic hematopoiesis
an autosomal recessive genetic disorder aka gray collie syndrome; severe neutropenia developing q10-14 days
what is dysgranulopoiesis
presence of dysplastic granulocyte progenitor cells that leads to peripheral neutropenia in presence of normal to increased progenitor cells in bone marrow
3 major classifications of dysmyelopoiesis
myelodysplastic syndrome, secondary dysmyelopoiesis, congenital dysmyelopoiesis
what is myelodysplastic syndrome
clonal expansion of mutated hematopoietic progenitor cell that results in apoptosis before being released from bone marrow;results in many blasts in marrow but insufficient cells in circulation
what is secondary dysmyelopoiesis?
similar to MDS except the number of blasts in bone marrow is not increased
what diseases or drugs have been assoc with secondary dysmyelopoiesis
IMHA, ITP, lymphoma, antineoplastic drugs, estrogen, phenobarbital, cephalosporins, chloramphenicol, lithium in cats, colchicine
in what breed does trapped neutrophil syndrome occur
border collies
how is the dx of immune mediated neutropenia often made?
exclusion of other causes; can use flow cytometry, detecting anti neutrophil Ab
what are the recommended antimicrobials in people with septic shock and neutropenia?
beta lactam and aminoglycoside
T/F: recombinant HUMAN G-CSF has been shown to be effective in dogs with parvo?
false
why is recombinant CANINE G-CSF not currently recommended?
lack of safety data; high mortality rate in dogs given the drug with parvovirus
Method to memorize the interleukins associated with Th1 and Th2 cells
- Macrophages can produce IL-1 which activates Th cells (CD4 T cells).
- If the macrophages also produce IL-12, this will drive the Th cells to become Th1 cells (2 to Th1, or “to” Th1).
- If Th1 cells are induced, they will produce IL-2 (second cytokine in order) and both IL-3 and IFN-gamma (gamma is the 3rd letter of Greek alphabet and represents the 3, too). The IFN-gamma will activate cytotoxic T cells (CD8 T cells).
- If the macrophages produce only IL-1, this will drive the Th cells to become Th2 cells. If Th2 cells are induced, they will produce IL-4, IL-5, and IL-6 (note that they follow in order) that drive B cells to divide and differentiate into plasma cells that produce antibody.
- Th2 cells also produce IL-10 (“zero Th1”) which blocks macrophage production of IL-12 and thus blocks activation of Th1 cells.
Name the three components to Virchows Triad
Endothelial dysfunction, hypercoagulability, blood stasis/altered flow
Name the major proteoglycan that makes up 50-90% of the proteoglycans responsible for binding antithrombin
Heparin sulfate
With inflammation, do glycoaminoglycans (GAGs) increase or decrease?
decrease
Once injured or activated, endothelial cells release what factor?
Von Willebrands
All coagulation is initiated through the interaction of tissue factor and what other factor?
VII
Name the three primary anti-coagulant proteins
Antithrombin, protein C, TFPI
Antithrombin is typically increase or decreased in inflammation?
decreased
Antithrombin is decreased by what three mechanisms?
Consumption, decreased production, or degredation by neutrophil elastase
Circulating Plasminogen is concerted to plasmin by what two fibrinolytic activators
Tissue type ctivator (TPA) and urokinase
T/F - Traditional PT/PTT tests reliabily test for hypercoagulabilty
false
Septic patients first become hypercoagulable by which means
consumption
T/F - In patients with spetic peritonitis, the presence of a coagulopathy is associated independently with increased odds of death
true
Name two of the most common inflammatory states leading to DIC in cats
Sepsis and pancreatitis
In patients with protein loosing nephropathy, roughly what percentage of pateint shave been reported to form thrombi
22% (50% post mortem)
In non-survivors of IMHA, what percentage of patients had thrombi?
45-80%
This circulating factor is a contributor to the procoagulant state of IMHA
TF (upregulation of TF gene in IMHA)
Arterial thromboembolism in cats is most often associated with what unerlying disease
cardiac
What percetnage of cariomyopathic cats with spontaneous echocardiographic contrast (smoke) are in a systemiccaly hypercoagulable state
50%
The highest rates of DIC occur in dogs with what neoplasm
hemangiosarcoma
Name the most likely initiator of coagulation in TBI patients
TF (brain tissue is very high in TF)
Unfractionated or low molecular weight heparins inhibits what specifically
thrombin
In dogs and cats with inflammatory conditions, a drop in circulating platelet count, or prolongation of PTT by what percentage should raise concern for early stages of consumptive coagulopathy
20% prolonged PTT
Name the two most common platelet inhibitor drugs used long term for thromboprophylaxis in cats with cardiomyopathy
Aspirin and clopidogrel
