Clinical pharmacology

Question 1

What is IVIg?

Answer 1

Human IgG (with trace IgA) purified from pooled plasma of 1000-15000 donors with a variety of 10^9 antigen specificities.

Question 2

What is the IgG composition of IVIg?

Answer 2

It is mostly monomers with <5% IgG-dimers. Most is IgG1 and IgG2. Up to 4% is IgG3 and 0.5% is IgG4.

Question 3

How is IVIg administered?

Answer 3

Intravenously, but increasingly administered subcutaneously since this can also be done at home

Question 4

What doses can IVIg be given in, and when is each given?

Answer 4

Low dose is given as replacement therapy such as in primary antibody deficiencies.
High dose is given in certain autoimmune diseases as immunomodulation.

Question 5

What IVIg dose is given to people with primary antibody deficiencies

Answer 5

Low dose as replacement therapy

Question 6

What is Kawasaki’s and what is used as therapy for this? How does this work?

Answer 6

Vasculitis of medium-sized vessels, causing necrosis. For therapy, first aspirin is given to reduce inflammation, then high-dose IVIg, which clears symptoms within 2 days.
In Kawasaki’s macrophages, neutrophils and DCs are activated through their Fcy receptors. IgG in IVIg blocks Fcy receptors through dilution.

Question 7

How does IVIg work in ITP?

Answer 7

ITP is caused by auto-antibodies against platelets, where macrophages in the spleen phagocytose them. IgGs bind to macrophage Fcy receptors, blocking them from being able to attack the platelets.

Question 8

What are the two routes by which IVIg has effects?

Answer 8

F(ab)2-dependent and Fc-dependent

Question 9

How does F(ab)2-dependent IVIg treatment work? (2)

Answer 9

IgGs can directly neutralize antibodies, cytokines, soluble receptors and toxins, and they themselves can bind to cells for cell depletion by NK cells and macrophages

Question 10

How does FcRn saturation work? What is it used for?

Answer 10

Harmful antibodies are able to persist due to the recycling function of FcRn. By saturating FcRn, these harmful antibodies can’t be recycled (as easily).

Question 11

How does IVIg expand Tregs?

Answer 11

Engagement of FcyRIIb on DCs increases production of IL-10 and TGF-ß

Question 12

Is complement inhibition Fc- or F(ab)2-dependent?

Answer 12

It can be both. F(ab)2 can directly bind and neutralise C3a and C5a and saturate out auto-antibodies that lead to complement activation.
Fc can bind to other complement proteins such as those involved in MAC, they can bind to FcyRIIb which upregulates inhibitory receptors, and bind to DC-SIGN on DCs which increases IL-10 production and thus dampens complement activation.

Question 13

How can IVIg modulate DCs?

Answer 13

They can bind to DC-SIGN through Fc and increase IL-10 production

Question 14

Which FcyR is found on neutrophils?

Answer 14

FcyRIIIB

Question 15

Which FcyR is inhibitory?

Answer 15

FcyRIIB

Question 16

How can IVIg be anti-inflammatory? (mechanism 1)

Answer 16

They can block binding of pathogenic immune complexes through activating FcyR on macrophages, NK cells and neutrophils

Question 17

What role does glycosylation play in FcR-mediated inhibition?

Answer 17

Composition of different sugars can determine affinity, where higher affinity binding can lead to more effective displacement of auto-antibody binding

Question 18

How does IVIg affect FcyRIIB expression and what is the significance of this?

Answer 18

It can upregulate inhibitory FcyRIIB expression, thereby inhibiting phagocytosis of (by antibody) opsonized cells and preventing potentially pathogenic degradation in the case of auto-antibodies.

Question 19

Are Fc studies in mice directly translatable to humans?

Answer 19

No, they have different Fc receptors and the anatomy of the spleen is different.

Question 20

Does IVIg expand Tregs?

Answer 20

No, but increases HLA-DR (activation) and foxp3 expression, leading to an enhanced suppressive capacity through IL-10 and TGF-ß.

Question 21

What is the mechanism of action of tacrolimus?

Answer 21

It is a calcineurin inhibitor downstream of signal 1 in T cells (MHC+peptide). This disrupts transcription of IL-2, thereby interfering with T-cell activation, proliferation, and differentiation.

Question 22

What are the main side effects of transplantation? (3)

Answer 22

• Surgery complications (bleeding, infection)
• Medication side effects (immunosupression)
• Negative effects of immunosuppression (infection, cancer, kidney damage)

Question 23

What is the most common type of cancer after transplantation?

Answer 23

Skin, especially squamous cell carcinoma. About half of patients have at least one skin cancer 20-25 years after transplant. A large proportion have >3 skin cancers every year.

Question 24

What is the main risk factor for developing skin cancer after transplantation?

Answer 24

Sunlight exposure

Question 25

What is an example as to why we should be careful interpreting database results of cancer risks in transplant patients?

Answer 25

If the question is: What would be the effect if we would lower immunosuppressive therapy after the first year of transplantation? You could do database research looking at graft survival and compare people that continued immunosuppressive therapy and those that reduced or withdrew altogether. When doing so, it was found that those who continued immunosuppression had a higher graft survival than those who reduced or withdrew altogether. However, it was not indicated whether those in withdrawal or deduction groups were already experiencing nephrotoxicity from the drugs and thus already had poor graft function.

Question 26

Is changing immunosupressive therapy the best strategy for reducing skin cancer?

Answer 26

It is not routinely done due to the risk for the transplant and the risk of side effects, since ~25% of patients do not toletate sirolimus. However, it does appear to reduce formation of skin cancer to a small degree, especially when done shortly after transplantation. The choice is different per person. Prevention of sunlight exposure is key.

Question 27

What is membranous nephropathy?

Answer 27

Glomerular disease that leads to protein and/or blood in the urine

Question 28

How can acute glomerular disease present?

Answer 28

Nephrotic or nephritic. Nephrotic is protein in the urine due to leakage or dysfunctional filtering, whereas nephritic is due to inflammation such as vasculitis or glomerulitis

Question 29

What type of acute glomerular disease is characterized by hematuria?

Answer 29

Nephritic syndrome. Urine can look like coca cola or smoky

Question 30

What is ANA testing?

Answer 30

It is used to detect autoantibodies that target components of the cell nucleus. It is primarily used in the diagnosis of autoimmune diseases, particularly systemic lupus erythematosus (SLE).

Question 31

What happens to podocytes in membranous nephropathy?

Answer 31

Foot processes are fused, and there are subepithelial deposits of immune complexes at the glomerular basement membrane.

Question 32

What causes GBM deposits?

Answer 32

Glomerular basement membrane deposits are caused by auto-antibodies against the M-type PLA2 receptors, which are transmembranous receptors in podocytes

Question 33

What is the result of membranous nephropathy?

Answer 33

Proteinuria, due to podocyte damage cause by auto-antibodies against receptors on podocytes, leading to immune complexes and complement activation

Question 34

What type of antibodies are those present in membranous nephropathy?

Answer 34

IgG4

Question 35

How can biopsies lead to diagnosis of membranous nephropathy?

Answer 35

Multiplex staining of IgG and PLA2R (the receptor to which the auto-antibodies bind), where overlap of these indicates the disease

Question 36

What is the best way to treat membranous nephropathy?

Answer 36

Anti-CD20 (Rituximab) to target B cells, including those that produce auto-antibodies. IVIg doesn't work because this is an IgG4-mediated disease, for which IVIg doesn't work well since IgG4 does not activate complement and is monomeric, so it only really neutralizes and does not induce Fc-dependent pathways. T cells can be targeted, such as with corticosteroids or calcineurin inhibitors.

Question 37

How to assess treatment response in membranous nephropathy patients?

Answer 37

Assess proteinuria levels (creatinine and albumin)

Question 38

What is hemolytic uremic syndrome?

Answer 38

A spectrum of syndromes that cause hemolysis and uremia.

Question 39

What are diagnostic signs of hemolytic uremic syndrome?

Answer 39

Signs of red blood cell lysis: Low RBC, hemoglobin present (shouldnt be in serum), fragmentocytes (fragmented blood cells). Also high creatinine due to the uremia.

Question 40

What are the 3 hallmarks or hemolytic uremic syndrome?

Answer 40

Microangiopathic hemolytic anemia Thrombocytopenia Acute kidney injury

Question 41

What are the histological indications for HUS?

Answer 41

Narrowing and blockage (by thrombi and red blood cells) of renal blood vessels

Question 42

What are the 4 underlying diseases that lead to HUS?

Answer 42

Co-existing diseases or conditions (transplantation, hematological malignancies, drugs) Infections (S. pneumoniae, e. coli shiga toxin, viruses) Cobalamin C defect Atypical HUS

Question 43

What is the most common cause of HUS?

Answer 43

STEC: Shiga toxin in e. coli. It causes 90% of HUS in children

Question 44

What is the pathogenesis of atypical HUS?

Answer 44

Atypical HUS is complement-mediated. Mutations lead to dysregulation of the complement system, particularly in the alternative pathway, where complement leads to destruction of RBC and endothelial cells

Question 45

What are two genes in which mutations can be found in atypical HUS patients?

Answer 45

Factor H (Can be due to a mutation or an antibody) -> regulates C3 Mutation in C3 itself Both lead to dysregulation of the alternative pathway

Question 46

What is the best and only targeted treatment (on the market) for atypical HUS?

Answer 46

Eculizumab. It prevents C5 cleavage and MAC formation