Immunology

Question 1

S100A12 - what is it, evidence in literature?

Answer 1

S100A12 = calgranulin C. Cytoplasmic damage-associated molecular pattern found predominantly in Np & Mp involved in activation of phagocytic cells.
Evidence:
- Faecal [S100A12] associated with disease activity in dogs with IBD.
- Serum [S100A12] increased in dogs with PLE or FRE.
- Serum [S100A12] positively correlated with dogs with higher hepatic necroinflammatory scores on liver bx (congenital PSS, CH, hepatic neoplasia)

Question 2

What are the 5 proposed mechanisms for improved platelet count with vincristine administration in IMTP?

Answer 2

LaQuaglia JVIM 2021
1) Fragmentation of megakaryocytes
2) Inhibition of platelet phagocytosis
3) Interference with formation of anti-platelet antibodies
4) Inhibition of anti-platelet antibody binding
5) Stimulation of thrombopoiesis

Question 3

List mechanisms for predisposition to PTE in IMHA?

Answer 3

1) Platelet dysfunction: dogs with IMHA have been shown to have hyperactive platelets associated with platelet plasma membrane alterations –> activated platelets release vasoactive molecules such as serotonin and thromboxane A2 –> may contribute to a hypercoagulable state.

2) Use of glucocorticoids

Question 4

Adverse effects of cyclosporine use in IMHA?

Answer 4

1) Increases TXA synthesis –> potentially increasing thrombogenic properties of platelets.
2) GI effects (common)

Question 5

Aspirin MOA?

Answer 5

Cyclooxygenase (COX) inhibitor -decreases TXA A2 synthesis & irreversibly inhibits platelet function. (COX enzyme is essential for conversion of arachidonic acid to several biologically
active prostaglandins (TXA A2) necessary for normal hemostasis).

Question 6

What is the difference between autoantibodies & alloantibodies?

Answer 6

Alloantibodies = immune antibodies that are only produced following exposure to foreign RBC antigens. Produced by exposure to non-self RBC antigens but are of the same species. They react only with allogenic cells.

Autoantibodies = antibodies that target **self antigens **present on the patient or donors’ own RBCs.

Question 7

What are eicosanoids & their key function?

Answer 7

Eicosanoids = lipid metabolites of arachidonic acid (AA).
Roles: mediate endothelial function, vascular reactivity & proteinuria. Anti-inflammatory. Also neuroprotective.

Question 8

How do neutrophil extracellular traps (NETs) form & what are their roles?
Which arm of the immune response do they belong?

Answer 8

After activation by LPS/CXCL8, Np release azurophil granule contents & release DNA strands, proteins, lysosomal enzymes into ECF –> collectively form a network of fibres (NETs).
NETs are coated with antimicrobial proteins, granule components; which physically capture bacteria & kill them.

Innate immune response.

Question 9

Name the associated with the following TLRs:
- TLR-2
- TLR-4
- TLR-5

Answer 9

• TLR2 recognizes lipopeptides and lipotechoic acid mainly found in the cell wall of G+ bacteria
• TLR4 recognizes lipopolysaccharide (LPS) present in the cell wall of G- bacteria
• TLR5 recognizes flagellin (main protein of bacterial flagella)

Question 10

What TLRs are upregulated in the duodenal & colonic mucosa of dogs with IBD?
Which breed has TLR polymorphisms associated with IBD, and which TLRs are they?

Answer 10

TLRs 2, 4, 9
GSDs. TLR 4 & 5.

Question 11

What is calprotectin (S100A8/A9) and what is its ligand?

Answer 11

DAMP, marker for neutrophilic inflammation.
Ligand = TLR-4 (type of PRR)

Question 11

What is calprotectin (S100A8/A9) and what is its ligand?

Answer 11

DAMP, marker for neutrophilic inflammation.
Ligand = TLR-4 (type of PRR)

Question 13

What is rheumatoid factor?

Answer 13

Autoantibodies against IgG.

Question 14

Leflunomide
- MOA
- AE

Answer 14

Active metabolite = teriflunomide. Inhibits DHODH = Dihydroorotate dehydrogenase (rate-limiting enzyme in de novo synthesis of pyrimidines)
May induce T reg production.

Mild-moderate GI toxicity
Myelosuppression: neutropenia, anaemia (rare – high doses)
Cutaneous drug reactions (can be severe – TEN, SJS), hepatotoxicity, respiratory signs (dyspnea, cough), pulmonary lesions (interstitial lung dz), lethargy, hyperchol

Question 15

Mycophenolate mofetil
- MOA

Answer 15

Selective & reversibly inhibits IMPDH = inosine monophosphate dehydrogenase (key enzyme in the rate of guanine monophosphate synthesis in de novo purine biosynthesis)
Selectively acts on activated T cells (IMDPH found in activated but not resting cells)
Inhibits B & T cell proliferation > reduces Ab pdtn

Question 16

Cyclosporin
- MOA
- TDM methods

Answer 16

• Binds to cyclophilin A (predominant cyclophilin within T-lymphocytes), forming a complex with high affinity for specific cell receptors on calcineurin –> inhibits calcineurin function –> blocks TCR-activated signal transduction pathway involved in transcription of cytokine genes (esp IL-2).
• Resultant decreased IL-2 expression in CD4+ Th1 cells –> blocks proliferation and activation of both helper and cytotoxic T-lymphocytes
• Overall suppresses cell-mediated immunity.
• Also suppresses IL-3, IL-4, TNF-α production; indirect suppressive effects on granulocytes, macrophages, natural killer cells, eosinophils, and mast cells. Also B cells.

TDM:
- PK – whole blood [ ]
- PD – functional assays analyzing T-cell activation & IL-2 & IFN-g suppression

Question 17

Which cytokine is responsible for eosinophil maturation & release from the BM?

Answer 17

IL-5

Question 18

What is the MOA of oclaticinib?

Answer 18

JAK inhibitor. Canine anti-IL-31 monoclonal Ab.

Question 19

Positive vs negative acute phase proteins?

Answer 19

Positive:
- Hepcidin
- SAA
- Ferritin (increased with anemia of inflammation)

Negative:
- Albumin
- Transferrin

Question 20

Antigen presenting cells - which 3?

MHC-I presents Ag to ….. while MHC-II presents to …..

T cells require which lympohokines?

Answer 20

Dendritic cells (prsent to T cells), dendritic cells, B lymphocytes

Cytotoxic T cells, T helper cells

IL-2 (Tc growth & proliferation)
Almost all ILs esp IL4 to IL6 (B cell activation - Ab response)
GM-CSF, IFN-g

Question 21

What is Felty’s syndrome?

Answer 21

Triad of rheumatoid (erosive) arthritis, splenomegaly, and neutropenia. Spleen is the site of immune-mediated neutrophil destruction, so splenectomy is a tx (for refractory cases).

Question 22

DDx for erosive polyarthropathy?

Answer 22

Rheumatoid arthritis (small dogs)
Greyhound erosive PA
Juvenile-onset PA (Akitas)
Shar Pei fever
Chronic progressive PA (cats)

Question 23

What serological markers can be useful in the diagnosis of SRMA? Are these prognostic?

Answer 23

Paired IgA in serum & CSF.
Older dogs with high CSF IgA levels tend to experience more frequent relapses and require longer duration of tx.

Question 24

Most common clinical signs in dogs vs cats with SLE?

Answer 24

Dogs: non-erosive PA > pyrexia, renal, skin > lymphaenopathy/splenomegaly > CNS (5%)
Cats: skin (60%), pyrexia > renal, non-erosive PA, CNS (24%), IMHA (24%)

Question 25

Diagnostic criteria for SLE?

Discuss interpretation of serum ANA titre in diagnosis of SLE.

What diagnostic test finding may support presence of anti-phospholipid antibodies with SLE?

Answer 25

Definitive dx = 2 major signs & positive ANA.
Probable dx = 2 major signs & negative ANA.

Major signs: polyarthritis, glomerulonephritis, haemolytic anaemia, leukopaenia, thrombocytopaenia, characteristic skin lesions, polymyositis
Minor signs: fever, CNS signs, oral ulceration, lymphadenopathy, pericarditis, pleuritis

ANA+ in >90% SLE cases; ANA >1:40 is positive but >1:256 is more supportive of SLE. (NB poor Sp as increased with any multi-systemic inflammatory dz, also 10% healthy animals will be ANA+)

Ab bind to cell-associated phospholipids –> interferes with the function of procoagulant phospholipids in clotting tests in vivo –> causes prolonged APTT (aka lupus anticoagulant) that fails to correct with a 1 : 1 mixture of the patient’s plasma and normal plasma