Tumor Immunity

Question 1

What are the two main types of tumor antigens?

Answer 1

TSA: tumor-specific antigens
TAA: tumor-associated antigens

Question 2

Which types of tumor antigens are tumor specific antigens?

Answer 2

Virus induced: cross reactive and immunotherapy should be applicable to all individuals infected with the cells
Chemical/physical carcinogen-induced : random mutations in affected cell causing AG differences - no cross protection

Question 3

Which types of tumor antigens are tumor associated antigens?

Answer 3

Oncofetal Ag/Carcinoembryonic antigen (CEA): high concentration disappear at birth and return in colorectal cancer
Oncofetal Ag/alpha-fetoprotein: Also expresed in liver during inflammation, high in fetal/maternal, low in adults

Question 4

What will tumor Ags activate when presented to to the naive cells by APCs?

Answer 4

T-cells

Question 5

When observed histologically, lymphocytes can be viewed around tumors and lymph nodes enlarge. What does this mean?

Answer 5

Immune like lymphocyte proliferation responses against tumors inhibit tumor growth

Question 6

If an immunodeficient individual has cancer what would you observe?

Answer 6

An increased incidence of certain types of tumors indicating the immune system protects against tumor growth
“immune surveillance”

Question 7

What does diminished T-cell function mean to the immune response in tumors?

Answer 7

CD4+ T cells can’t secete cytokines that activate macrophages and CD8+ T cells
No CTL mediated tumor eradication

Question 8

When a transplant is rejected by an animal previously exposed to a specific tumor what occurs?

Answer 8

Immunity tumor transplants can be transferred by lymphocytes from a tumor-bearing animal
Tumor rejection is mediated by lymphocytes

Question 9

How do CD8+ T cells in the adaptive immune system respond to tumors?

Answer 9

Perform immune surveillance function recognizing and killing potentially malignant cells that express peptides derived from tumor antigens ad are presented with class I MCH

Question 10

How do CD4+ T cells in the adaptive immune system respond to tumors?

Answer 10

Secrete IL-2 to activate CTLs and IFN-g to activate macrophages

Question 11

How do antibodies in the adaptive immune system response to tumors?

Answer 11

Mediate antibody-dependent cell mediated cytotoxicity (ADCC) so Fc receptors-bearing macrophages or NK cells mediate killing

Question 12

How does the NK cell respond to tumors in innate immunity?

Answer 12

Kills many tumor cell types, espeically with reduced class I MHC expression
ADCC and lysis
IL-12, IL-15 and IFNg inc killing
Lymphokine-activated killer (LAK) cells - IL-2

Question 13

How does a macrophage respond to tumors in innate immunity?

Answer 13

M1: classically activated inhibit tumor growth via TNF inducing thrombosis in tumor vessels

Question 14

How do tumors escape immune response?

Answer 14

Losing expression of Ags
Down regulating MHC-1
Producing immunosuppressive cytokines
Tumor arising in immunologically privileged site

Question 15

How can tumor gene evade by failure to produce tumor antigen?

Answer 15

Antigen-loss variant of tumor cell

Causes the T-cell to be blind to the tumor cell

Question 16

If a tumor cell lacks an MHC gene what occurs?

Answer 16

The T-cell cannot recognize it

Question 17

If a tumor produced an immunosuppressive protein (inhibitory ligand PD-L1) what occurs?

Answer 17

T-cell action is inhibited

Question 18

Tumor associated macrophages

Answer 18

M2: alternatively activated to promote tumors and spread of cancers by altering tissue micro-environment and suppressing T-cell responses
IL-10, prostoglandin E2, arginase, TGF-B and VEG-F

Question 19

Regulatory T cells

Answer 19

Suppress T-cell response to tumors
Number of T-regs inc in tumor-bearing individuals and these cells are found in the cellular infiltrates of certain tumors

Question 20

Myeloid-derived suppressor cells (MDSCs)

Answer 20

Suppress anti-tumor innate and T-cell response

Question 21

How can tumors be eradicated by the same effector mechanisms used to eliminate microbes?

Answer 21

Opsonization and phagolysis, activation of complement system and ADCC
ex: Anti-CD20 in B cells lymphoma pts

Question 22

What are some ways anti-tumor monoclonal antibodies and destroy tumors?

Answer 22

Eradicate tumors the same way as microbes

Use antibodies that can directly activate intrinsic apoptosis pathways in tumor cells

Question 23

Which antibody is specific for oncogene product HER2/Neu?

Answer 23

mAB Herceptin

Elicits an immune effector mechanism and interferes with growth signaling functions of HER2/Neu

Question 24

How can there be adoptive transfer of tumor-specific T cells?

Answer 24

Lymphoctes isolated from the blood or tumor infiltrate of a pt
Expanded by culture in IL-2
Infused back into pt
Tx often combine w/ systemic IL-2 admin - some tumor regression

Question 25

What are some say to enhance tumor suppression responses?

Answer 25

Vaccinating with tumor cells transfected with genes encoding B7 costimulators or cytokine genes
Vaccinate with tumor-antigen presenting dendritic cell
Vaccinate w/ plasmids containing complementary DNAs encoding tumor antigens that are injected directly into pts or use direct transfer of dendritic cells