Final exam VTPB 409

Question 1

Cell- Mediated Immunity (slide 3)

Answer 1

the form of adaptive immunity that is mediated by T lymphocytes and serves as the defense mechanism against microbes that survive within phagocytes or infect non-phagocytic cells

CMI is usually developed against intracellular microbes

The two types of cells affected by CMI are phagocytic and nonphagocytic cells

Question 2

Examples of intracellular microbes

Answer 2

Bacteria: Mycobacteria, Listeria monocytogenes, Legionelia pneumophila

Fungi: Cryptococcus neoformans

Protozoa (phagocytic): Leishmania, Trypanosoma cruzi

Rickettsiae: All

Viruses: All

Protozoa (nonphagocytic): Plasmodium falciparum, Cryptosporidium parvum

Question 3

Cell- Mediated Immunity (slide 4)

Answer 3

CMI responses include CD4+ T-cell mediated activation of macrophages that have phagocytosed microbes and CD8+ CTL- mediated killing of infected cells

One characteristic of the adaptive immune system is specialization so there are two different mechanisms: it can be presented by the helper T cell or the cytolytic T cell and when this happens, cytokines are activated.

Each mechanism leads to both an effector and memory cell.

CD4 activates macrophages and other cells, CD8 kills infected cells

Question 4

Stages of CMI

Answer 4

1. antigen recognition
2. activation
3. clonal expansion
4. differentiation
5. effector functions

Question 5

CMI Against Intracellular Microbes (slide 6)

Answer 5

Effector T helper cells of the Th1 and Th17 subsets recognize microbial antigens and secrete cytokines that recruit leukocytes (inflammation) and activate phagocytes to kill the microbes

The APC will present to the helper T cell and it responds by production of cytokines. They can be classified by the cytokines that are produced.

T helper cell type I will produce cytokine secretion which helps macrophage to become a better killer

T helper cell type 17 will produce cytokine secretion which leads to inflammation and killing of microbes

Question 6

Types of T cell- Mediated Immune Reactions (slide 8)

Answer 6

CD8+ cytotoxic T lymphocytes (CTLs) kill any infected cell containing microbial proteins in the cytosol or nucleus, eliminating cellular reservoirs of infection

If the APC presents to the CD8 cell, it becomes an effector cell and takes direct action and kills the infected cell

CD4 cells indirectly affect the eradication of microbes but CD8 cells directly attack the infected cell

Question 7

Subsets of CD4+ helper T lymphocytes (slide 9)

Answer 7

T helper cell type 1 mainly produces interferon gamma. The target cells are macrophages, host defense are intracellular pathogens and the role in disease is autoimmunity and chronic inflammation

T helper cell type II produces IL-4, IL-5, and IL- 13. The target cells are eosinophiles. The host defense are parasites (helminths), and the role in disease is allergy.

T helper cell type 17 produces IL- 17, IL- 22. The target cells are neutrophils. The host defense are extracellular pathogens, and the role in disease is autoimmunity

Question 8

Development & Characteristics of Subsets of CD4+ Helper T cells (slide 10)

Answer 8

Great source of questions, refer to chart.

We have 3 types of helper T cells and they all are classified only on the cytokines produced

Question 9

What antibody isotypes are simulated in the Th1 cell type?

Answer 9

complement and Fc receptor- binding IgG subclasses such as IgG2a (mouse)

Question 10

What antibody isotypes are simulated in the Th17 cell type?

Answer 10

?

Question 11

What antibody isotypes are simulated in the Th2 cell type?

Answer 11

IgE; IgG1 (mouse), IgG4 (humans)

Question 12

What is the macrophage activation of Th1 cell type?

Answer 12

classical (microbial killing)

Question 13

What is the macrophage activation of Th2 cell type?

Answer 13

alternative (tissue repair)

Question 14

What is the macrophage activation of Th17 cell type?

Answer 14

?

Question 15

What are the dominant leukocytes recruited for Th1?

Answer 15

Monocytes

Question 16

What are the dominant leukocytes recruited for Th2?

Answer 16

eosinophils

Question 17

What are the dominant leukocytes recruited for Th17?

Answer 17

neutrophils, monocytes

Question 18

The development of Th1, Th2, and Th17 cells (slide 11)

Answer 18

The APC presents to the naive CD4+ T cell.
The ctyokines IFN-gamma and IL- 12 will produce a Th1 response (antigen presentation and cellular immunity)
The cytokine IL-4 will lead to Th2 cells.
The cytokines TGF-beta, IL-6, and IL-23 will produce a Th17 cell.

Question 19

The functions of Th1&Th2 subsets of lymphocytes (slide 12)

Answer 19

????

Question 20

The Main DIfferences between Th1&Th2 subsets

Answer 20

IFN gamma activates Th1 and inhibits Th2 activity. IL-4 inhibits Th1 and activates Th2.

Question 21

The differentiation of Naive Cd4+ Tcells into Th1&Th2 Effector ceells

Answer 21

????

Question 22

The function of Th17 cells(slide 15)

Answer 22

Th17 produces Il-17 and IL- 22. Il-17 recruits inflammatory cells. ex: psoriasis

IL-22 functions to support the innate immune system. It produces antibiotic peptides (chemical barriers used by the innate immune system- ex: lysozymes in the tears of your eyes

Question 23

Cell Mediated Immunity (slide 18)

Answer 23

CMI is a form of immunity to an intracellular bacterial infection that could be transferred from immune animals to naive animals by cells (now known to be T lymphocytes) but not by serum antibodies)

It was known from the earliest studies that the specificity of CMI against different microbes was a function of the lymphocytes, but the elimination of the microbes was a function of activated macrophages.

Question 24

The induction&effector phases of CMI

Answer 24

APC presents to cd4 and cd8 cells and are recruited to the lymph node in the hope of meeting an infected cell and becomes an effector cell. In CMI, T cells recognize protein antigens at two stages
First, naive T cells recognize antigens in lymphoid tissues and respond by proliferating and differentiating into effector cells

Second, effector T cells recognize the same antigens anywhere in the body and respond by eliminating these microbes.

Question 25

The induction&effector phases of CMI

Answer 25

APC presents to cd4 and cd8 cells and are recruited to the lymph node in the hope of meeting an infected cell and becomes an effector cell. In CMI, T cells recognize protein antigens at two stages
First, naive T cells recognize antigens in lymphoid tissues and respond by proliferating and differentiating into effector cells

Second, effector T cells recognize the same antigens anywhere in the body and respond by eliminating these microbes.

Question 26

Peripheral Lymphoid Organs (slide 23)

Answer 26

in the follicles, you find the B cells, APC meets cell in the medulla? morphology of the spleen, refer to slide

Question 27

Migration of T lymphocytes

Answer 27

The lymph node has an artery filled with blood. Naive cells are circulating in the blood and also the effector T cells. Both of them go into the lymph node. The effector cell has already met its microbe so it will easily leave. The naive T cell will hang around and is hopeful to meet its match and become an effector cell. Goes into circulation as an effector cell. Selectin will show up in the endothelial cell.

Question 28

Migration of Naive & Effector T Lymphocytes (slide 25)

Answer 28

Naive T cells express the adhesion molecule L-selectin and the chemokine receptor CCR7, which mediate selective migration into lymph nodes through specialized vessels call HEVs.
Effector T cells so not express CCR7 or L-selectin, and thus they are not drawn into lymph nodes

Question 29

Migration of Naive & Effector T Lymphocytes (slide 26)

Answer 29

The phospholipid, sphingosine 1-phosphate (S1P), plays a role in the exit of T cells from the lymph nodes, by binding to the receptor, called S1PR1 (type 1 sphingosine 1-phosphate receptor)