E2 Specific immunosuppression

Question 1

Define ALG

1. where derived from
2. short term target
3. long term target

Answer 1

Anti-Lymphocytic Globulin

1. large animals purifying IgG
2. Small long-lived Peripheral Lymphocytes circulating between Blood and lymph node
3. Thymus-dependent lymphocytes from the “Cuffs” of lymphoid Follicles depleted as they participate in recirculating pool

Question 2

Define ALG

1. Describe Mechanism

2. cellular consequences

Answer 2

Anti-Lymphocytic Globulin

1. Bind to surface of Ag-recognising Tc/ Cytotoxicity by serum complement
2. Specific destruction of T, consequent impairment of DTH, (Ab response intact)

Question 3

Define ALG

1. Describe side effects

2. limitations of use

Answer 3

Anti-Lymphocytic Globulin
1. serum sickness: Ag-Ab precipitates in kidney –> body removes by complement = Ab damage
Lymphoma at injection site
2. eventually due to side effects ALG becomes ineffective - therefore first line treatment: stops organ being rejected in first instance but not long term strategy

Question 4

Describe cyclosporin A

• what type of molecule
• describe structure
• what advantage does it provide
• side effects

Answer 4

• Macrolide
• 11 membered ring of peptide a.a
• w/ CsA kidney doesnt need to be tissue matched
• ~toxicity/ nephrotoxicity

Question 5

Decribe the 3 Macrolide molecules

what must they all be bound to

Answer 5

Cyclosporin A
FK-506
Rapamycin
- all agonists which induce a state of immunosuppression
(their binding protein to produce protein complex)

Question 6

name Macrolide antagonists

Answer 6

L-685,818
506BD
- prevent the immunosuppressive action of macrolide agonists

Question 7

cyclosporin A - provides

potent suppression of:

Answer 7

• alloantigen-specific Tc no. (Tc against antigen)
• T-cell proliferation
• cytotoxic Tc no.
• IL-2 & IFNy

Question 8

Describe FK506

• how much more potent than CsA
• side effects

Answer 8

clinically identical to CsA
100x potency
same as CsA but nephrotoxicity less ~due to smaller dose

Question 9

Describe rapamycin

• when effective
• potency compared to FK506
• side effects

Answer 9

Effective even after Tc activation
Especially highly histoincompatible organs (heart)
Greater potency & graft survival time than FK506
No major renal toxicity but: in experimental animals can lead to
- GI ulceration/
- vasculitis
- testicular atrophy

Question 10

Name the binding receptor for CsA, FK506 and rapamycin

what are the type of binding proteins & describe function

Answer 10

CsA binds cyclophilin
FK506 and rapamycin bind FKBP

• pepidyl-prolyl isomerases (PPIs) –> Rotamases
  (enzymes which catalyse the rotatation of protein as folded which helps formation of tertiary structure)

Question 11

Is inhibiting rotamase activity correlated to immunosuppression
- how was this shown

Answer 11

No as antagonist which themselves have no intrinsic activity are able to inhibit rotamases
There rotamase activity not involved in suppression

Question 12

Explain the effect of CsA and FK506 on calcineurin

Answer 12

Inhibits calcineurin (a phosphatase) from removing the P from NFATc therefore cant translocate to nucleus (therefore can contribute to (Tc?) DNA formation - (no transcription/ production of Il-2 –> no Tc)

(calcineurin is key to Tc activation)

Question 13

How does rapamycin prevent cell cycle progression

Answer 13

Rapamycin (SRL) binds FKBP which inhibits mTOR
this prevents:
- ribosomal protein activation (S6 kinase)
- Cyclins (control cell cycle progression)
- cyclin dependent kinases (cdk & elF4F)
- ultimately inhibits cell cycle at G1 preventing S phase –> prevents cell cycle progression

Question 14

summary of observations CsA/ FK506

Answer 14

A) Affect Ca2+ pathways
B) Inhibit Ca2+ ionophores i.e. direct Ca2+ (in making intracellular Ca available) - work at step after Ca generation.
C) Do not affect generation of Ca2+ (affects its subsequent release)
CsA/ FK506 target pathways after Ca2+