Hematology

Question 1

Cyclosporine use as immunosuppressive

Answer 1

Primarily IMHA, but also RA, ITP, myositis

Question 2

Azathioprine MOA?

Answer 2

Purine analog, metabolized to ribonucleotide mono phosphates. Accumulation of mono phosphates leads to negative feedback on enzymes required for purine synthesis

Question 3

Does aza have a better effect on humoral or cell- mediated immunity?

Answer 3

HUMORAL.

Question 4

What is major side effect of aza in cats

Answer 4

Myelosuppression

Question 5

MOA of methotrexate

Answer 5

Inhibits folic acid reductase resulting in decreased purine and pyrimidine synthesis

S phase specific

Question 6

What cancer is methotrexate used to treat?

Answer 6

Lymphoma, carcinoma, sarcoma

Question 7

What are the MOAs of steroids?

Answer 7

Stabilize endothelial cell membranes, inhibit production of local chemo tactic factors, decrease infiltration of neutrophils, monocytes, lymphocytes.

Inhibit release of amino acids from membrane phospholipids- no synthesis of membrane prostaglandins, thromboxanes, leukotrienes

Suppress T cell activation and cytotoxicity, suppress cytokines activity and alter macrophage function

Question 8

MOA of cyclosporine?

Answer 8

Inhibits calcineurin to inhibit calcium dependent signal transduction

Bound in cytosol of lymphocytes by cyclophilins. Cyclosporine- cyclophilins complexes associate with calcium- dependent calcineurin calmodulin complexes to impede calcium dependent signal transduction. Transcription factors that promote cytokines gene activation are indirect or direct substrates of calcineurin. This results in inhibition of early T cell activation (G0 cell cycle) and prevents synthesis of IL-2, resulting in inhibition of T-cell proliferation and decreased T cell cytotoxic activity.

Also stimulates Tgf- B production which is an inhibitor of IL2 stimulated T cell proliferation and generation of antigen- specific cytotoxic lymphocytes

Question 9

Which suspension is 4% bioavailable in dogs? Sandimmune or neoral

Answer 9

Sandimmune. It is a oil suspension and sucks. Neoral is a micro emulsion and more bioavailable

Question 10

When to measure cyclosporine blood levels?

Answer 10

12 hour trough level

In humans they do 2 hrs post administration

Question 11

Side effects of cyclosporine?

Answer 11

Hepatotoxicty- when waaaay high blood levels are present. RARE.
Nephrotoxic- RARE in cats. Super super rare in dogs.

Can promote development of neoplasia especially lymphoma ESP when used w pred

In dogs: severe gingival hyperplasia, fibropapillomas, severe or fatal pyoderma

Question 12

Side effects of aza?

Answer 12

Bone marrow suppression, pancreatitis, hepatotoxicty

Question 13

Cyclophosphamide MOA

Answer 13

Alkylating agent- S phase specific

Question 14

Tacrolimus MOA

Answer 14

This is a calcineurin inhibitor too- lymphocyte specific

Binds in the cytosol to an immunophilin, FK-binding protein

The tacrolimus FKBP complex binds to calcineurin and inhibits its phosphatase activity (cycle does this too but in a diff way). This results in inibition of de novo expression of nuclear regulatory proteins and T cell activation genes. The transcription of cytokines (IL- 2, IL-3, IL-4, IL-5, interferon gamma, tumor necrosis factor alpha and granulocyte-macrophage colony-stimulating factor) are suppressed, as is suppression of IL-2 and IL-7 receptors.

Tacrolimus is 50-100x potent compared to cyclosporin. IT inhibits B cell proliferation and production of antibody- MOA unknown.

Question 15

Toxicities of tacrolimus

Answer 15

super toxic! vasculitis leading to myocardial infarction, liver failure, intussusception, anorexia

Question 16

MOA sirolimus, rapamycin, everolimus

Answer 16

These are macrocyclic antibiotics with a structure similar to tacrolimus that bind in the cell cytosol to FKBP. Sirolumus works by blocking activation of mTOR- a serine/threonine protein kinase involved in regulation of cell proliferation

Prevents cell from progressing from G1 to S phase, and blocks T cell activation by IL-2, IL-4, IL-6 and stimulation of B cell proliferation by lipopolysaccharide. Sirloins also directly inhibits B cell immunoglobulin synthesis caused by interleukins.

These inhibit the proliferation of fibroblasts, endothelial cells, hepatocytes, and smooth muscle cells induced by growth factors such as platelet-derived growth factor and fibroblast growth factors.

Question 17

Toxicity of sirolimus

Answer 17

When given with cyclosporine, increased risk of nephrotoxicity, hemolytic uremic syndrome, hypertension. Hyperlipidemia, thrombocytopenia, delayed wound healing, delayed graft function, mouth ulcers, pneumonitis, and interstitial lung disease.

Question 18

Mycophenolate MOA

Answer 18

hydrolyzed in the liver to mycophenolic acid. Cytostatic to lymphocytes due to inhibition of inosine monophosphate dehydrogenase, an enzyme necessary for de novo purine biosynthesis. It’s a relatively selective inhibitor of B and T cell proliferation during S phase of cell cycle.

May also inhibit growth- factor induced smooth muscle and fibroblast proliferation.

Question 19

Mycophenolate toxicity

Answer 19

GI hemorrhage, anorexia, diarrhea.

Question 20

Leflunomide

Answer 20

synthetic organic isoxazole that the intestinal mucosa metabolizes to A77-1726.

The active drug works at the S phase of the cell cycle to inhibit de novo pyrimidine biosynthesis via dihydrorotate dehydrogenase

It’s also an inhibitor of tyrosine kinases associated with growth factor receptors

Has effects on B and T lymphocytes, and also has an anti proliferative effect on smooth muscle cells and fibroblasts.

Question 21

Toxicity of leflunomide?

Answer 21

GI toxicity via actions of trimethylfluoroanaline (metabolite)

Question 22

One odd use of leflunomide

Answer 22

It may be useful in the treatment of reactivation of latent feline herpesvirus 1 infection that occurs secondary to the stress of injury, illness, surgery, or immunosuppression.

It has cytostatic, antioxidant, and apoptotic effects in humans and may play a role in cancer chemoprevention

Question 23

What are the major diagnostic criteria for IMHA

Answer 23

spherocytosis, autoagglutination and strongly regenerative anemia

Question 24

What are other abnormalities in dogs with IMHA

Answer 24

hyperbilirubinemia, leukocytosis, thrombocytopenia, elevated liver enzymes

Question 25

What is the mechanism of RBC destruction in IMHA

Answer 25

Extravascular hemolysis: destruction by macrophages in the spleen caused by antibodies coating surface of RBC

Intravascular hemolysis: complement-mediated lysis, mediated by IgM antibodies activating complement.

No matter what mechanism of RBC destruction, from the standpoint of therapy, IMHA is primarily a CD4 T cell driven disorder.

Question 26

Triggers for development of IMHA

Answer 26

few proven- vaccination, infection, tissue injury, drug therapy
may be genetic susceptibility.
spring and early summer more common.

Question 27

Can you detect circulating anti-erythrocyte antibodies in the serum of affected dogs w IMHA?

Answer 27

NOT usually. But easy to find Ig on surface of RBC with flow cytometry.

Usually antibodies involved are IgG or IgG AND IgM.
IgM alone is really are.

Question 28

Which antibodies bind surface of RBC in IMHA

Answer 28

IgG or IgG and IgM. IgM alone is super rare

Question 29

What percent of dogs with IMHA have platelet activation?

Answer 29

75% have activated platelets, as assessed by up-regulation of P-selectin expression

Question 30

What is one mechanism of development of Evan’s syndrome possibly?

Answer 30

Anti-RBC antibodies are commonly detected in dogs with thrombocytopenia, suggesting that cross-reactive antigens may be present in dogs with immune-mediated platelet destruction.

Question 31

What is the prevalence of thromboembolic disease with IMHA?

Answer 31

30-50%, but probably higher.

Question 32

What are some negative prognostic factors for survival with IMHA

Answer 32

hyperbilirubinemia, thrombocytopenia, leukocytosis, esp with increased bands

Other ones identified (but not as commonly) are azotemia, petechiation, hypoalbuminemia
Degree of anemia, magnitude of retic response, and degree of spherocytosis was not associated with outcome.

Question 33

Which acute phase proteins are high with IMHA?

Answer 33

alpha-1-acid glycoprotein, and C-reactive protein.

Question 34

Which serum cytokines are high in dogs with IMHA?

Answer 34

IL-15, IL-18, GM-CSF, MCP-1. And MCP-1 found to be increased and associated with higher risk of death in dogs.

Question 35

What is mechanism of action of unfractionated heparin?

Answer 35

Binds to AT which enhances its activity and leads to inhibition of factors II and Xa. Pharmacokinetics of this drug are super variable.

Monitor response to therapy with PTT measurement- should be 1.5-2.5x baseline.

Question 36

How does low-molecular-weight heparin work?

Answer 36

Inhibits function of factor Xa but does not block the activity of thrombin. Thus, the likelihood of inducing unintended hemorrhage with LMWH is much lower than with unfractionated heparin.

Question 37

How does plavix work?

Answer 37

Irreversible inactivation of a subtype of the adenosine diphosphate receptor on the membrane of platelets- the result is decreased platelet aggregation

Question 38

How does IVIG work?

Answer 38

Unknown. But it has immunosuppressive effects that involve signaling through immunosuppressive receptors on macrophages.