Integrating Basic and Clinical Immmunology

Question 1

four mechanisms by which the immune system destroys malignant cells

Answer 1

• opsonin mediated phagocytosis
• natural killer cell recognizing a problem directly through receptors/MICA
• NK cells binding an antibody bound to an antigen present on the surface
• cytotoxic T cells

Question 2

four T cell defects or dysfunction that allow tumors to evade the immune system

Answer 2

1. Hole in the repertoire
2. Lack of costimulatory molecules
3. Lack of Type 1 cytokines
4. Increase in Tregs

Question 3

ten tumor related phenomenon that allow tumors to evade the immune system

Answer 3

1. Shedding of Tumor Antigens
2. Antigenic Modulation (endocytosis)
3. Antigen Masking
4. Loss of Antigenicity (tumors not seen as foreign)
5. Secretion of Immunosuppressive Molecules
6. Immunologically Privileged Site
7. Loss of Class I MHC Expression
8. Shed MICA
9. Upregulation of CD200
10. Upregulation of PD-L1/L2

Question 4

three limitations to “Adoptive transfer of T cells with Engineered/Redirected T cell Receptor”

Answer 4

• Restricting therapy to patients with “correct” MHC
• Need tumor to present antigen in MHC groove
• MHC down regulation common in tumors

Question 5

how are chimeric antigen T cell receptors (CARs) generated

Answer 5

Take V/D/J of a monoclonal antibody and then you need CD3 signaling (remember T cells signal through CD3). So now you have a T cell that can be everything a T cell can do only now it recognizes antigen without MHC (so you dont have to worry about the fact that cancer down regulates MHC anymore). Still have the CD28 costimulatory molecule.

Question 6

what are the advantages of CARs (chimeric antigen T cell receptors) and how do they overcome the limitations of “Adoptive transfer of T cells with Engineered/Redirected T cell Receptors”

Answer 6

-No MHC required so this overcomes tumor down regulation and no need to match patient’s MHC type (allele)

Question 7

Pulsed dendritic cells (in vitro) with either tumor lysates or recombinant tumor antigens and subsequent transfer back into the patient is an accepted therapy for some cancers. What is the rationale for pulsing dendritic cells and returning them to the patient?

Answer 7

Provenge is one of the treatments and it works through drawing the patient’s own immune cells and culturing them, with a prostate specific in this case, specific antigen and then reintroducing them with the hopes of stimulating the immune system to attack and destroy the same antigen displaying cells

Question 8

Explain the process that must occur in vitro for dendritic cells to present antigen to both CD8+ T cells as well as CD4+ T cells

Answer 8

Dendritic cells generally present exogenous antigens to CD4+ T cell. So in order for presentation to CD8+ T cell there needs to be a cross presentation on class I MHC event occurring.

Question 9

In another approach to cancer therapy, dendritic cells are isolated from the patient, expanded in vitro and transferred back into the patient–into malignant tissue damaged with heat and radiation or cyrotherapy. Explain the underlying principle for this therapy

Answer 9

Dendritic cells are removed and expanded to increase number – heat/radiation/cryotherapy used to destroy malignant tissue which then releases antigens – dendritic cells then reintroduced in order to acquire those antigens and stimulate immune response

Question 10

What are some potential side effects of this lymphodeletion?

Answer 10

Vitiligo and Autoimmune destruction of melanocytes in the eye

Question 11

Explain the term TILs and why these T cells are derived for expansion in vitro prior to subsequent adoptive transfer to the patients

Answer 11

TILS- Tumor Infiltrating Lymphocytes (of T cells)

these cells are grown in the lab (under the assumption that if the cells are in the tumor site they must have some specificity for the tumor antigen) and then they grow these T cells that recognize tumor antigen with a little IL-2 cytokine to keep the cells grow and place them back into the patient

Question 12

Antibody therapy for cancer

1. Anti-CTLA Antibody (Ipilimumab): Recombinant

Answer 12

i. T-cells activated by costim of CD28 (T-cell) with CD 80/86 (APC), but after a few days the T cell expresses CTLA-4 which has higher affinity for CD80/86 → T cell inhibition
ii. Making an antibody against the CTLA4, keeps it from binding CD80/86 and turning off. Maintain active T cells

Question 13

How would ipilimumab (anti-CTLA4 antibody) be beneficial in generating an immune response to eliminate the cancer cells (metastatic melanoma)?

Answer 13

So again restoring T cell activation in order to eliminate the cancer cells

Question 14

Antibody therapy for cancer:

2. Pidilizumab: anti- PD1 antibody (humanized)

Answer 14

i. similar mechanism in that PD-1 (Tcell) binds PD-L1/2 (presenting cell) resulting in T cell deactivation
ii. Antibodies for the PD-1 inhibit this interaction and thereby increase/maintain T cell activation

Question 15

Antibody therapy for cancer:

2. Pidilizumab: anti- PD1 antibody (humanized)
   Again how would this be beneficial in generating an immune response to eliminate the cancer cells

Answer 15

again so the normal response of T cells are eventually to be turned off and this happens via PD1- PDL1/2 interaction. But with this treatment an antibody is made called Anti PD1 (and it binds to PD1) you eliminate this PD1-PDL1/2 interaction and the T cell continues to kill tumor cells.

Question 16

Antibody therapy for cancer:

3. Samalizumab: anti-200 antibody (humanized) 3

B chronic lymphocytic leukemia and multiple myeloma

Answer 16

Normally CD200 is expressed on the T cells, B cells and dendritic cells

CD200R is mainly on your myeloid cells (monocytes, macrophages and dendritic cells)
Once this interaction between CD200 and CD200R happen cells can be turned off

Tumor cells have upregulation of the CD200 and this is a protective thing for the tumor having CD200 now cells can be turned off or suppressed.

The treatment Anti-CD200 places an antibody on the tumor cell and this CD200 is blocked from sending a negative signal to the receptor CD200R

Question 17

Anti-BlyS, a human monoclonal antibody, for the treatment of systemic lupus erythematosus (SLE) was approved for the treatment of SLE. What is the mechanism of this drug

Answer 17

Anti-BlyS antibodies bind BLyS and prevent it from binding to BR3 on B cells. Cells that have been activated will undergo apoptosis (no longer protected from apoptosis) because remember at the end of the day the formation of immune complexes is the problem with this autoimmune disease.

Question 18

Rituximab is used for active Rheumoid Arthritis and has been used off label for SLE (systemic lupus). What is the mechanism by which the drug mediates its effects? three ways of killing

Answer 18

All via an Anti-CD20 antibody (remember CD20 is a B cell restricted cell surface antigen)
1. Phagocyte-opsonin mediated phagocytosis through Fcgamma-FCgamma R
2. Granules containing perforin and granzymes through ADCC NK cells
3 .Complement Activation- MAC

basically think in terms of IgG

Question 19

So why give this drug CTLA4-Ig (Abatacept) to a patient with RA, if CTL4 is going to turn off this drug anyways?

Answer 19

normally binding of CTLA4 occurs after T cells are activated and have released cytokines, so it doesnt help you much in the beginning.

With Abatacept, you prevent T cells from ever being activated. So you prevent CD28 interacting with CD80 in the first place.

Question 20

Remicade, humicade, humira, and simponi are all antibodies that bind TNF and used for RA. What is the mechanism of action for these drugs?

Answer 20

They have specificity for TNF, and bind it. This absorbs it and leaves less for signaling of the TH1 pathway or upregulation of inflammation/Th1/etc

Question 21

what is the advantage of a human or humanized antibody (Versus a chimeric or a murine )

Answer 21

Murine and Chimeric are highly immunogenic (then it’s humanized then human)

Human and Humanized are least likely to produce an immune response against the antibody after repeated injections

Question 22

How does administration of these antibodies (Remicade, humicade, humira, and simponi) help in reducing inflammation?

Answer 22

well they capture TNF and without TNF the vascular endothelium can not be activated for an inflammation response.

Question 23

Natalizumab (anti-VLA4) is a humanized antibody that is approved for the treatment of remitting relapsing MS. Explain the mechanism of this drug

Answer 23

This anti-VLA4 antibody is going to actually block the interaction of VCAM-1 with VLA-4 and this is going to now prevent entry of the cell (diapedesis) into the CNS. So this activated T cell just stays in the blood now.

Question 24

In regards to anti-VLA4 treatment, what side effects would this cause?

Answer 24

PML (progressive multifocal leukoencephalopathy) – most people are carrying the virus and now because someone is on this drug and therefore immunosuppressed now the virus can easily activate.

Question 25

Zanapax/Daclizumab (anti-IL 2R/anti-CD25) is a humanized antibody that is approved as a current treatment option for MS. What is the mechanism for Zanapax?

Answer 25

antibody that blocks differentiation of T cells. but does not block Tregs

remember IL2 is your growth factor for your T cells so if your blocking the receptor then no T cells

Question 26

what are some negative consequences of Zanapax?

Answer 26

well again this therapy is trying to block differentiation of T effector cells but does not block Tregs

nTregs downregulate your immune system to self and foreign antigen

a/i Tregs downregulates immune system by downregulating CD4+ and CD8+ T cells

Question 27

Ustekinumab and Briakinumab are anti-p40 antibodies (anti-IL12 and anti IL23). Explain why these drugs (Antibodies) bind both IL12 and IL23 with the same specificity and what their effects are

Answer 27

IL12 is a dimer (p40 + p35), IL23 also contains p40(+p19) so they bind with the same specificity because of the p40

binding of the p40 keeps IL12 from activating NK cells so decrease IFNgamma and down reg maturation/differentiation to TH1 cells.

Blocking of IL23, inhibits stabilization of TH17 cells

Question 28

In stage II clinical trials these anti-40 antibodies (Ustekinumab and Briakinumab) did not show efficacy for MS. However this drug was shown to work for another disease?

Answer 28

Psoriasis

Question 29

What are xenografts?

Answer 29

Transplantation refers to the engraftment of cells or tissues from one individual (donor) to another (recipient/host)

In an xenograft these are grafts that are species specific

Question 30

How and why do xenografts lead to hyperacute rejection

Answer 30

This reaction reflects the existence of natural antibodies in man to carbohydrates present on the transplanted pig organs.

(remember xenografts are species specific)

Question 31

Daclizumab, a humanized antibody and Basiliximab, a chimeric antibody, both bind to CD25 (Anti-CD25). What is the rationale for administering either of these agents to prevent/overcome acute rejection?

Answer 31

IL-2 is needed as growth factor for T cells – CD25 aka IL-2 receptor if bound by antibody cannot bind to IL-2 hence no growth factor for T cells — downregulation of T cells which will prevent acute rejection

prevents clonal expansion of activated Tcells
prevents development of pCTLs –> activated CTLs and NK cells to LAK cells

Question 32

what is another mechanism for abatacept for inhibition?

Answer 32

Going to phagocytose APC so you therefore deplete B7 expressing cells.

Question 33

what is the downside to the administration of therapeutic agents that block the effect of TNF?

Answer 33

Fungal Infections and death

Question 34

Eculizumab is (anti C5 antibody) a humanized antibody for the treatment of patients with PNH. What is the mode of action of Eculizumab?

Answer 34

this is going to block C5 now with C5 blocked a MAC complex is not formed, a PNH red cell will be protected from undergoing intravascular hemolysis, but once opsonized by C3 it will become prey to macrophages

Question 35

why would eculizumab help patients with PNH?

Answer 35

Remember that in patients with PNH they are lacking this glycosyl phosphatidylinositol linkage to two regulatory proteins CD55 (blocks C3 convertase) and CD59 (blocks MAC) on the RBC. without these proteins the red blood cell will now be lysed by the activated complement pathway

Question 36

What type of infections are these patients susceptible too when adminstered this anti C5 antibody (eculizumab)?

Answer 36

Neisseria (remember any defect in MAC the only bacterial species that will be an issue will be Neisseria)

Question 37

Patients who are receiving eculizumab should receive what before taking the drug?

Answer 37

patients tend to develop meningococcal infections quite often on this drug so therefore patients should receive a meningococcal vaccination at least 2 weeks prior to receiving the drug.

Question 38

Xolair (omalizumab) is a recombinant, DNA-derived, humanized IgG monoclonal antibody that binds selectively to human IgE constant region. It was approved for patients with moderate to severe asthma and who have a positive skin or blood test to allergens in the air. What is the mechanism of Xolair?

Answer 38

this drug is going to bind to the IgE to inhibit the bind the FceRI binding site to the FceRI receptor site. This receptor site is located on the mast cell and basophil. Without this interaction you get a lack of release of allergic reaction mediators such as histamine and leukotriences and therefore without this release stops inflammation and constriction of airways.

Question 39

side effects from Xolair?

Answer 39

well you have no release of allergic reaction mediators so patient is highly susceptible to allergic reactions or even basic allergies

Question 40

How and why do xenografts lead to hyperacute rejection

Answer 40

This reaction reflects the existence of natural antibodies in man to carbohydrates present on the transplanted pig organs.

Question 41

Explain why the porcine complement regulatory proteins do not protect the tissue from destruction?

Answer 41

Human cells lack an alpha 1, 3 galactosyl transferase, and this antigenic epitope does not exist in humans, so no tolerance is established. Exposure of the immune system during development to this antigen induces high levels of anti alpha 1,3 galactose antibodies in all humans.

Question 42

Patients with X-SCID have a mutation in CD132 which signals via JAK3. This is an immunodeficiency disorder. Despite this, patient have had allograft transplants have been enrolled in a clinical trial for treatment with a JAK 3 inhibitor. Explain the rationale underlying this treatment and why would it benefit patient enrolled in this clinical trial

Answer 42

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Question 43

what are the possible side effects of Daclizumab therapy

Answer 43

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Question 44

although the ABO blood group antigens are regarded as RBC antigens, they are actually expressed on a wide variety of human tissues. Name two tissues

Answer 44

epithelial and endothelial cells

Question 45

Explain the cause of hyperacute rejection

Answer 45

performed antibodies to donor antigens mediate hyperacute rejection, occurring in minutes to hours post transplant.

Question 46

what is the mechanism of tissue damage?

Answer 46

The existence of preformed antibodies indicates that the recipient has previously been immunized, intentionally, or unintentionally against antigens for the donor tissue.

Question 47

T cells can be redirected to selectively kill cancer cells by introducing T cell receptors that recognize specific cancer antigens in complex with MHC. The altered T cells are transferred ¬¬¬back into the patient (“adoptive transfer of T cells”). Adoptive transfer of altered T cells results in anti-tumor activity in some, but not all cancers suggesting tumor escape mechanisms by the cancer cell.

Predict: which tumor escape mechanism/s would hamper the anti-tumor activity for which this therapy was designed.

Answer 47

loss of class I MHC expression