21 17-19

Question 1

C+C Class I and Class II MHC

Answer 1

DISPLAYED BY All nucleated cells APC

RECOGNIZED BY Naïve CD8/Tc CD4

FOREIGN Ag Endogenous — Exogenous

MESSAGE Kill Me/if Tc, look at what I found — Mount an attack

Question 2

CD4

Answer 2

Usually become helper T cells that help activate other B cells, other T cells, macrophages and direct the adaptive immune response. A couple become regulatory T cells. Bind only to class II MHCs

Question 3

CD8

Answer 3

Become cytotoxic T cells that destroy any cells in the body that harbor anything foreign. Bind only to Class I MHCs.

Question 4

C+C T cells and B cells first lambs

Answer 4

FUNCTION Intracellular patho—Extracellular patho

IMMUNITY cell mediated—humoral mediated

RECEPTOR TCR—antibodies

SECRETORY PRODUCTS Cytokines–Antibodies

TERRITORY Infected body cells—-Blood/Lymph

LIFE SPAN Long——-short

ACTIVE CELLS Th/Tc/Treg——plasma cells

MEMORY yes——yes

BIRTHPLACE Bone marrow——Bone marrow

SCHOOL Thymus——Bone marrow

Question 5

Cell-mediated immunity

Answer 5

Immunity conferred by activated T cells which directly kill infected of cancerous body cells and release chemicals that regulate the immune response.

Question 6

T cells can only recognize?

Answer 6

Antigens displayed on APCs

Question 7

Dendritic cells can display antigens on both?

Answer 7

MHC I and MHC II

Question 8

What is the stimulus for clonal selection and differentiation of T cells?

Answer 8

Binding of antigen and co-stimulation

Question 9

2 step process of T cell activation

Answer 9

1. Double recognition

CD4 cell recognizes antigen-MHC complex. Both the TCR and CD4 proteins bind to it.

2. Co-stimulation - must also bind one or more co-stimulatory signals. (i.e dendritic cells sprout B7 proteins on their surfaces when innate defenses are mobilized)

If the signal is not received, the T cell becomes tolerant/wont divide/won’t secrete cytokines to that antigen (unresponsive = anergy)

Without this safeguard, MHC I proteins that are displaying peptides from within the cell could activate cytotoxic T cells leading to damage of healthy cells.

Question 10

Proliferation and Differentiation of T cells

Answer 10

When activated by antigen and co-stimulation, a T cell proliferates becoming memory cells and effector cells. Cytokines released by APCs or Ts promote the process.

Question 11

Cytokines

Answer 11

Language of immune system - mediate cell development/differentiation/responses of immune system.

Includes Interleukins and interferons.

Question 12

Interleukin I

Answer 12

source: macrophage

Activity: Activation of T cells and macrophages, promotion of inflammation and fever

Question 13

Interleukin II

Answer 13

Source: Helper Ts

Activity: Activation of lymphocytes, NK cells and macrophages

Question 14

Roles of Helper T cells

Answer 14

Stimulate proliferation of other T cells and B cells that are bound to antigens.

1. Activation of B cells
2. Activation of CD8 cells
3. Amplification of Innate defenses
4. Subsets of Th cells

Question 15

How do helper cells help in humoral immunity?

Answer 15

Th cell binds with a B cell that has encounted its antigen and is displaying it on MHCII.

Th cell releases interleukins as co-stimulatory signals to complete B cell activation.

Question 16

How do helper cells help in cellular immunity (with CD8)?

Answer 16

1. previously activated Th cell binds to a dendritic cell.
2. Th cell stimulates dendritic cell to express co-stimulatory molecules needed to activate CD8 cell.
3. Dendritic cell can now activate CD8 cell with the help of interleukin 2 secreted by Th cell.

Question 17

How do cytotoxic cells work?

Answer 17

1. Tc binds tightly to target cell when it identifies foreign antigen on MHC I protein.
2. Tc releases perforin and granzyme molecules from its granules by exocytosis.
3. Perforin molecules insert into the target cell membrane and form a hole. Granzymes enter the target cell via the pores. Once inside they degrade cellular contents stimulating apoptosis.

Question 18

Cellular immunity flowchart - CD4

Answer 18

Ag infected body cell engulfed by dendritic cell becomes APC –>

activates naïve CD4 –>

clones give rise to memory and helper T –>

2 processes:

1. Helper T cytokines stimulate nonspecific killers (macrophages and NK cells of innate sys.)

OR

2. Helper T cells co-stimulate and release cytokines in response to B cells that present Ag to helper cell This causes an increase in B cell division.

Question 19

Cellular immunity flowchart - CD8

Answer 19

Ag infected body cell engulfed by dendritic cell becomes APC –>

activates naïve CD8 –>

clones give rise to memory CD8 and Cytotoxic T cells –>

together the nonspecific killer (macrophage/NK) and cytotoxic T cells attack the Ag

Question 20

What are CD4 and CD8s?

Answer 20

cell differentiation glycoproteins

Distinct from antigen receptors!

Question 21

MHC restriction

Answer 21

CD4 cells are restricted to binding antigens only on class II MHC

CD8 are activated by fragments on MHC I and after activation look for the same antigen on class I MHC located on any cells of the body.