Immunology/Hematology Flashcards
What is the normal platelet number per HPF in dogs?
8-15 platelets/HPF (120 - 225K/uL)
*Each platelet = 15,000/ platelets/uL
What is methemoglobin?
A type of hemoglobin that the iron on the heme has been oxidized from ferrous (Fe2+) to ferric (Fe3+)
When there are >30% methemoglobins in the circulation, what does the pulse oximeter usually show? Why?
85% (even if PaO2 is high)
Methemoglobins absorb both wavelengths of light very well.
What are the two type of reticulocytes in cats? Which one can be seen up to 10% in healthy cats?
Aggregate reticulocytes & Punctate reticulocytes
Punctate reticulocytes can be seen in healthy cats
* Aggregate forms are released from the marrow and, after approximately 12 hours, develop into punctate forms that persist in the circulation for 9–20 days.
Where does ferritin exist and what is its function?
Ferritin exists in all cells
It stores iron and acts as a reservoir to prevent excessive intracellular ion causing cell damage.
What is the function of Hepcidin?
It is secreted by hepatocytes and inhibits iron export from enterocytes, macrophages, and hepatocytes.
↑ production during iron overload
What is the function of transferrin?
Transport iron
For Transferrin and Ferritin, which one is positive acute phase protein and which one is negative acute phase protein?
Transferrin: negative acute phase protein
Ferritin: positive acute phase protein
What is the lifespan for canine and feline RBCs?
Dog: 120 days
Cat: 80 days
What is the lifespan of platelets?
5-7 days
What is the lifespan of neutrophils?
< 24 hours
What is the function of haptoglobin?
It binds to free hemoglobin in the circulation
True or False: Hemoglobin has 2 𝜶 globins and 2 𝜷 globins, all of which contains heme molecules.
True
Which iron can bind to oxygen, ferric or ferrous?
Ferrous (Fe2+) can bind to oxygen
Ferric (Fe3+) cannot
What does 2,3-DPG do?
It decreases hemoglobin affinity to oxygen.
What is Heinz bodies?
Damaged hemoglobins (usually from oxidative damage)
What is phosphofructokinase (PFK) deficiency and what is the treatment?
Periodic intravascular hemolysis and hemoglobinuria associated with strenuous exercise or stress-induced hyperventilation causing respiratory alkalosis
Treatment: exercise restriction
What is pyruvate kinase (PK) deficiency?
Decreased ATP availability due to lacking of PK → hemolysis
Moderate to severe macrocytic hypochromic anemia with marked reticulocytosis → myelofibrosis → non- regenerative anemia
- Worse prognosis compared to PFK deficiency
List 10 causes of hemolysis.
1) Primary IMHA
2) Mycoplasma haemofelis infection
3) DIC
4) Splenic neoplasia
5) Hypophosphatemia
6) IV hypotonic fluid bolus
7) Phosphofructokinase deficiency
8) Pyruvate kinase deficiency
9) Uremic-hemolytic syndrome
10) Onion ingestion
11) Zinc, copper toxicity
Which type of hypersensitivity is associated with IMHA?
Type II
Describe neonatal isoerythrolysis.
It happens in kittens - when type B queen mated to a type A male and the kitten is type AB or A.
When kitten is nursed with the queen’s colostrum, the can absorb the antibodies against type A epitope. About 12-24 hours after colostrum ingestion, the antibodies against type A epitope will be in the circulation and attack kitten’s RBCs
What is the equation for corrected reticulocytes?
Corrected reticulocytes = Measured reticulocytes x (PCV/N)
*In dogs, N = 45; in cats, N = 37)
After a BM insult, which cell line decrease will be observed first?
Granulocytes → Neutropenia (5-6 days later)
Thrombocytopenia (8-10 days)
What is the function of hepcidin?
It regulates the iron metabolism and availability.
Increased hepcidin → decreased iron availability
Positive acute phase protein
What is the definitive of RBC regeneration in dogs?
Reticulocytes > 60K/uL
What is the common sequela of Pyruvate kinase (PK) deficiency?
Myelofibrosis
Osteosclerosis
Hemosiderosis-induced hepatic failure or bone marrow failure
Does canine and feline RBC contain mitochondria?
No
What is normal RBC:WBC ratio?
500:1
How to calculate HCT?
HCT = MCV x RBC/10
Name 3 oxidizing agents in the neutrophils
Superoxide (O2−)
Hydrogen peroxide (H2O2)
Hydroxyl ion (OH )
- one of the lysosomal enzymes, myeloperoxidase, catalyzes the reaction between H2O2 and Cl- to form hypochlorite, which is exceedingly bactericidal.
During inflammation, what is the first line to four line defense mechanism of the body.
1) Tissue macrophage
2) Neutrophil Invasion of the Inflamed Area
3) Second Macrophage Invasion Into the Inflamed Tissue
4) Increased Production of Granulocytes and Monocytes by Bone Marrow
How many days does it take for the newly formed granulocytes and monocytes reach the stage of leaving the bone marrow?
3-4 days
What are the 5 factors that are mainly responsible in control of macrophage response (to stimulate BM)?
1) TNF-𝜶
2) IL-1
3) GM-CSF
4) G-CSF
5) M-CSF
Name two cells that can release eosinophil chemotactic factors.
Mast cells
Basophils
Name 4 substances mast cells (and basophils) release during inflammation.
Heparin
Histamine
Bradykinin
Serotonin
Name 4 components of innate immunity.
1) Phagocytosis of bacteria by neutrophils & lymphocytes
2) Stomach acid and digestive enzymes destroy the swallow organisms
3) Skin as a barrier to invaded organisms
4) Certain chemicals in the blood that attach to foreign organisms or toxins and destroy them (e.g. complement complex, lysosome, basic polypeptides, natural killer lymphocytes)
What are the two main types of acquired/adaptive immunity?
Humoral immunity (B cell immunity)
Cell-mediated immunity (T cell immunity)
Fill out the blank.
In normal body, how many percentages of immunoglobulins are IgG?
75%
Name four ways of antibodies destroy antigens directly.
1) Agglutination
2) Precipitation
3) Neutralization
4) Lysis
Write down the classic pathway of complement.
1) antibody attached to antigen - Fc portion binds to C1
2) c5b, C6, C7, C8, C9 form membrane attack complex
3) C3b opsonin for macrophage
Which complement protein cause opsonization of bacteria?
C3b
What is the complement protein compose the membrane attack complex (MAC)?
C5b6789
- MAC inserts itself into lipid bilayers and makes holes on the cell → cell lysis
Which complement protein initiate chemotaxis of neutrophils and macrophages?
C3a and C5a
Name three complement protein fragments that can activate mast cells and basophils.
C3a
C4a
C5a
What are the three major antigen presenting cells in the body and what is the site where the antigen bind to?
Macrophage, B lymphocyte, dendritic cell (accessory cell)
MHC protein (Major histocompatibility complex)
What are the two types of MHC protein and what is the main difference?
MHC I protein - all nucleated cells have it
MHC II protein - only antigen-presenting cell have it
Which type of T cells is the most abundant in the body?
T helper cells
Which interleukin has strong positive effect for the proliferation of cytotoxic T cells and regulatory T cells?
IL-2
Produced by activated T-helpers
Which three interleukins are called B-cell stimulating factors or B-cell growth factors?
Produced by TH2:
- IL-4 (B-cell clonal expansion)
- IL-5, IL-6 (development of plasma cells and antibody production)
True or False: CD4 T cells are mainly cytokine-secreting helper cells, whereas CD8 T cells are mainly cytotoxic killer cells.
True
T-cytotoxic cells recognize MHCI with viral antigen on tissue cells - interact via CD8 and activate perforins + granzymes to cause cell apoptosis
True or False: CD4 T cells can be divided into two major types. Type 1 (Th1) helper T cells secrete interleukin-2 and interferon-𝛄 but not interleukin-4, 5, or 6. Type 2 (Th2) helper T cells secrete interleukin-4, 5, 6, and 10 but not interleukin-2 or interferon-𝛄.
True
What are the three complement pathways? What is the activator for each pathway?
1) Classic pathway: pathogen, antibody-antigen complex to C1 via Fc portion
3) Alternative pathway: C3b binds directly to antigen and then C5b, 6,7,8,9 bind to C3b to then form membrane attack complex (no antibodies involved)
2) Lecithin pathway: antigen containing mannose binds lecitin which then binds C4 and trigger complement cascade
How many spherocytes/x100 oil immersion field support immune-mediated destruction of RBC?
> 5 spherocytes/x100 oil immersion field
(Sen: 63%; Spe 95%)
In the ACVIM Consensus Statement of IMHA, what are the 4 evidences of hemolysis?
Hyperbilirubinemia
Ghost cells
Hemoglobinemia
Hemoglobinuria
True or False: Saline agglutination testing performed by mixing 4 drops of saline with 1 drop of blood has a reported specificity of 100% for IMHA in dogs.
True
True or False: There is a high level of evidence that immune-mediated destruction of erythrocytes contributes to anemia in dogs infected with B. canis
False
B. gibsoni (from fighting)
In the ACVIM Consensus Statement of IMHA, it states that the evidence of M. haemofelis causing IMHA in cats is high.
True
What is the non-associative cause of IMHA? What about associative?
Non-associative: primary, cryptogenic
Associative: secondary
True or False: According to the ACVIM Consensus Statement of the treatment of IMHA, fresh RBC or at least no older than 7-10 days is recommended for use in dogs with IMHA.
True
According to the ACVIM Consensus Statement of the treatment of IMHA, what is the recommended dose for prednisone? If the dog is responding to the tx and is on > 2 mg/kg/d, when should you taper it?
2-3 mg/kg/d or 50-60 mg/m^/d (for dogs > 25 kg)
* Dex SP 0.2-0.4 mg/kg/d if cannot tolerate oral med
After 1-2 week
According to the ACVIM Consensus Statement of the treatment of IMHA, what are the 4 conditions when second immunosuppressant is recommended?
1) Severe, life-threatening IMHA
2) First 7 days the HCT decreases ≥ 5% in 24 hours (on pred)
3) Dependent on blood transfusion after 7 days (on pred)
4) Severe side effects from prednisone
List 4 drugs as second immunosuppressant for canine IMHA and their dose.
Azathioprine - 2 mg/kg or 50 mg/m2 PO q24h
Mycophenolate - 8-12 mg/kg PO q12h
Cyclosporine - 5 mg/kg PO q12h
Leflunomide - 2 mg/kg PO q24h
- They recommend cyclophosphamide not be administered to dogs with IMHA.
According to the ACVIM Consensus Statement of the treatment of IMHA, what is the recommended intervention if the dog does not respond to second immunosuppressant after 7 days?
IVIG 0.5-1g/kg single dose
According to the ACVIM Consensus Statement of the treatment of IMHA, if dog’s PCV/Hct has remained stable and >30% for 2 weeks after commencing treatment, what is the recommended tapering plan?
Taper prednisone by 25%, and by 25% every 3 weeks thereafter
- If there is a second immunosuppressant → don’t change the dose of that drug
According to the ACVIM Consensus Statement of the treatment of IMHA, what is the recommended management for asymptomatic neutropenic patients?
If the neutrophil count is between 1000 and 3000 cells/μL → no antibiotics unless other independent risk factors for infection are present
If the neutrophil count is <1000 cells/μL → prophylactic antibiotics
What is the relapse rate for IMHA?
11-15%
List 5 complications of IVIG administration.
1) Anaphylaxis
2) Acute kidney injury
3) Hypotension
4) Fluid overload
5) Thromboembolism
6) Aseptic meningitis
What is the recommended dose for IVIG?
0.5 - 1.5 g/kg IV over 4-8 hours
How does hepcidin affect iron?
Decreased iron availability
- Decrease GI absorption
- Prevent iron release from hepatocytes and macrophages
- Increase cellular internalization and degradation of ferroportin
Is ferritin a positive or negative acute phase protein? What does it do? What about transferrin?
Ferritin
- positive acute phase protein
- blood protein that contains iron
Transferrin
- negative acute phase protein
- main protein in blood that binds and transports iron
Name 2 poor prognostic indicators for IMHA and ITP.
IMHA
HighBUN level
Hyperbilirubinemia
ITP
High BUN level
Melena
What is a triad of symptoms for hemolytic-uremic syndrome? What is the cause?
Thrombocytopenia
Acute renal impairment (e.g. glomerular necrosis)
Microangiopathic hemolytic anemia
It is caused by Shiga-like toxin produced by E. coli (typical from), other bacteria, medication, immune processes
What metal on the pennies minted after 1982 can lead to hemolysis?
Copper
In cats, nonregenerative anemias with macrocytic normochromic red blood cells may be suggestive of what type of infection?
FeLV
In patients with IMHA, there are extravascular hemolysis and intravascular hemolysis. What immunoglobulin is associated with each and how does the hemolysis occur?
Extravascular hemolysis
- IgG
- IgG-RBC complex is cleared through the reticuloendothelial system
Intravascular hemolysis
- IgM
- IgM-RBC complex activates C3 and membrane attack complexes, induces the classical complement pathway, and results in intravascular hemolysis.
How are interferons synthesized?
When a virus invades a cell it can activate transcription factors for interferons:
- 𝛼 (from tissue cells)
- 𝛽 (from tissue cells and platelets)
- 𝛾 (from lymphoid cells)
Functions of interferons
- 𝛼 and 𝛽 elicit transcription of antiviral peptides in nearby cells and can activate NK cells for viral elimination
- 𝛾 recruitment and proliferation of more macrophage and hyperexpression of MHCII for antigen presentation
“Naive” B-cell resides in the ___ and gets exposed to ____ from lymphatic circulation.
Antigen binds to ___ it activates ___ which facilitates endocytosis.
Processing of the antigen results in expression of ____
lymph node
free-antigens
IgD (work as receptor)
clathrin-coded pits
specific MHC II
Once the B-cell expresses specific MHCII it is an antigen-presenting cell
Interaction between antigen-presenting cell and “naive” T-lymphocytes
- primary stimulus by interaction between MHCII +CD4 and MHCII+receptor
2.co-stimulus: B7 on presenting cell + CD28 on T cell
- third signal: IL-1 produced by presenting cell working on T-cell receptor
After this interaction T”naive” becomes an “activate Th” cell
Activated T-helper cells can differentiate in Th1 if stimulated by ___ and will mainly produce ___ vs if stimulated by ___ will develop into Th2 and mainly induce production of ___
IL-12
Inf 𝛾
IL-4
antibodies by B-cells and plasmacells
Function of NK cells
Kill the same way as Tcytotoxic with granizymes and perforins but will recognise cells without MHCI, cells with MICA (similar to MHC) and cells with antibodies attached
Briefly describe T-cell development
- produced in bone marrow
- T-cell precursor from BM to thymus driven by chemokines
- once in thymus, thymic cell produce chemokines to induce RAG and RAG2 factors in Tcells and consequent expression of receptors
- positive selection for Tcell able to express receptors for both MHCI and MHCII molecules
- negative selection for Tcell expressing receptors for self antigens
- if Tcell express receptor only for MHCII it becomes a Th (CD4)
- if Tcell express receptor only for MHCI becomes a Tcytotoxic (CD8)
Some T cells can become T regulatory under IL-2 influence and express CD-25
Phagocytosis is ___ process mediated by ___
These activate:
1.
2.
3.
4.
energy-dependent
small G-coupled proteins of the Rho family
- re-arrangement of cytoskeleton for endocytosis and formation of phagosome
- expression of phagocytes oxydase (ROS formation in the phagosome)
- iNOS activation in phagosome
4 protease activation in phagosome
Where is erythropoietin produced? what stimulates it?
It is produced in some proximal tubular cells under the influence of HIF (hypoxic inducible factor).
HIF is a transcription factor that is released from its binding protein only in hypoxic conditions
Bohr effect vs Haldane effect
Bohr = ↑ H+ induces decreased affinity of Hb for oxygen
Haldane = ↑O2 induces displacement of CO2 from Hb
2,3 DPG
byproduct of cell glycolysis
negatively charged so binds to positive 𝛽chains
Keeps Hb tight = in a tense state (lower O2 affinity)
Relationship between NO and Hb
DeoxyHb in the tense state releases NO vs in the relaxed state NO can stay hidden in Hb pocket
Useful for local vasodilation in hypoxic states
Cats have higher levels of 2,3 DPG than dogs
False
Cats have very little 2,3 DPG
According to ACVIM consensus what conditions are necessary to have a definitive diagnosis of IMHA?
- 2 or more signs of immune-mediated destruction
* >5 spherocytes /hpf
* positive SAT without washing
* positive Coombs
OR
* positive SAT with wasing - 1 or more signs of hemolysis
* ghost cells
* hemoglobinuria
* hemoglobinemia
* increased Tbil
If only 1 sign od immune-mediated destruction but no hemolysis evidence the diagnosis is “suspected” vs if 2 signs of immune mediated destruction and no signs of hemolysis or 1 sign of immune mediated destruction and 1 of hemolysis the diagnosis is “supportive of IMHA”
Coomb’s sensitivity and specificity for IMHA
Specificity 95-100%
Sensitivity lower at 62% in dogs and 82% in cats
SAT specificity and sensitivity
Sensitive (100%) but less specific (95%)
According to ACVIM consensus with infections diseases have good evidence demonstrating a causative relationship with IMHA?
- B. gibsoni in dogs
*M. felis and B. felis in cats
Cyclosporine is NOT myelosuppressive
True
Pathogenesis of IMTP
- IgG mediated targeting platelet receptors (GPIIb/IIIa)
- complement-mediated (without ab formation) via cytotoxic destruction
The presence of platelet/megakaryocytes antibodies is considered diagnostic for IMTP
False
Dogs with non-immune-mediated thrombocytopenia had increased ab levels
However trending the ab titers can help identify IMTP relapse in patients under treatment
Thrombopoietin levels in IMTP
A recent paper showed inappropriately low levels of thrombopoietin in primary IMTP and the relevance of using trombopoietin agonist agents like eltrombopag and romiplostim.
Diagnosis of IMTP according to ACVIM consensus
- confirm plt count < 100
- rule out bleeding/consumption/genetic macrothrombocytes
- verify if any other cytopenias and underlying diseases (i.e. sepsis, DIC) –> possible secondary IMTP
- Investigate and rule out possible underlying causes of IMTP (i.e. infectious, neoplastic) –> possible, probable or definitive IMTP diagnosis
- perform antibody test to have support of “immunological evidence”
According to ACVIM consensus there are 6 levels of diagnosis for primary IMTP and 4 level of diagnosis of secondary IMTP
- primary IMTP
*possible with or without immunological evidence
* probable with or without immunological evidence
* definitive with or without immunological evidence - secondary IMTP
* possible
* probable with or without immunological evidence
Recommended screening for IMTP investigations
In dogs: babesia, anaplasma, leishmania, angiostrongylus. distemper, septic foci
In cats: FIV/FeLV, anaplasma. ehrlichia, babesia, other infectious foci
Drugs that can induce IMTP
sulfonamides, cefazoline and gold salts
According to the ACVIM consensus how is response to treatment defined in IMTP patients
- remission: plt>100 with no evidence of bleeding and no medication needed
- complete response: plt>100 and no clinical signs but still on meds
- partial response: plt>30 but <100 AND X2 times plt count from presentation AND no clinical signs
- no response: plt<30 and/or clinical signs 2 months post initiation of treatment
Relapse incidence in IMTP
9-47% depending on rapidity of corticosteroid weaning (not related to length of treatment or treatment regime)
What is ROMIPLOSTIM
Thrombopoietin agonist
Do not use in cats
IVIg mechanisms of action
Immune modulation with decreased cytokines expression, blocking Fc receptors. eliminating pathogenic antibodies, inhibiting complement
Diseases in which IVIg has been shown to be beneficial
- IMHA: short term improvement but no long term outcome improvement
*IMTP: rapid increase in plt count and preferred to vincristine if sole treatment - myastenia gravis: short term benefits, but short-lived and accompanied by significant side effects
Cryopreserved and lyophilized platelets
Both have short post-transfusion life spans with cryopreserved ones lasting a bit longer (1-2h) vs lyophilised (only minutes). However, lyophilised ones have better functionality than cryopreserved ones.
Canine Albumin transfusion improved SI but not BP and can be associated with high rated of reactions (20%)
True
PROMMTS and MATTERS trials vs PROPRR trials
PROMMTS and MATTERS support higher ratios of plasma and platelets vs 1:1:1 vs PROPPR did not
