Immuno Final

Question 1

What is the function of Th17 cells in the immune defense?

Answer 1

Th17 cells produce IL-17 to recruit neutrophils for the destruction of fungi and some bacteria. Th17 releases IL-17, IL-21 (for GF of Th17), IL-23 (for B cell class switching to IgA and IgG3).

without IL-17 = devasting fungi infection

Question 2

What is the significance of regulatory T cells (Tregs) in immune homeostasis?

Answer 2

Tregs suppress unwanted immune responses and maintain tolerance to self-antigens.

-Subset of CD4s
-Intermediate binding during self-recongition phase.
-Happens in Thymus
-Foxp3 expression for transcription factor (peripherals)

Natural: Inhibit naive T cell activation
Inducable Treg: inhibit APC to bind to T cells for activation and reduces hypersresonse to invaders

Question 3

How is tolerance established during T and B cell development?

Answer 3

Through positive selection for functional receptors and negative selection against self-reactivity.

Question 4

What is the significance of CD28 and CTLA-4 in T cell signaling?

Answer 4

CD28 provides necessary co-stimulatory signals for activation, while CTLA-4 inhibits T cell activation by outcompeting CD28 for B7.

Question 5

How do IgE antibodies mediate hypersensitivity reactions?

Answer 5

IgE binds to allergens and activates mast cells and basophils, leading to the release of mediators during an allergic response.

Type 1 with basophil, mast cells and eosinophils. IgE will bind to FceRI on mast cells and basophils, if enough binds it will activate the cells.

Question 6

What role do APCs play in the activation of naive T and B cells?

Answer 6

APCs present antigens and provide co-stimulatory signals necessary to activate naive T and B cells.

Question 7

How do MHC I and MHC II differ in terms of structure and function?

Answer 7

MHC I presents to CD8+ T cells (cytotoxic), while MHC II presents to CD4+ T cells (helper).

Question 8

What happens to T cells during activation-induced cell death (AICD)?

Answer 8

AICD eliminates T cells that have been repeatedly activated, making space for new naive T cells.

Fas-FasL -> suicide or homicide (NTK)

Question 9

What mechanisms do T cells employ to avoid attacking self-antigens?

Answer 9

T cells undergo negative selection and require additional co-stimulation to become activated against pathogens.

Question 10

What is the significance of co-receptors in T cell activation?

Answer 10

Co-receptors like CD4 and CD8 determine the type of T cell and help in recognizing peptide-MHC complexes.

Question 11

What is the role of Th cells in orchestrating the immune response?

Answer 11

Th cells orchestrate the immune response by releasing cytokines that activate and direct other immune cells.

• Activate B cells to prodice Ab and Plasma cells
• Growth factor release
• Cyokines to recuit other immune cells

Question 12

What is the role of CD40 and CD40L in B cell activation?

Answer 12

CD40 on B cells interacts with CD40L on T helper cells, facilitating B cell activation and antibody production.

Question 13

How does molecular mimicry contribute to autoimmune diseases?

Answer 13

TCR/BCR may recognize pathogens but also cross-react with self-antigens, leading to autoimmunity. Since immune system may still be active, it will attack self angtigens that look like the pathogen that is dead.

Question 14

Why is a co-stimulatory signal required in T cell-dependent activation?

Answer 14

To ensure both the B cell and T cell recognize danger and agree on the need for an immune response.

Question 15

What are the main types of T cell memory and where do they reside?

Answer 15

Tissue-resident memory T cells remain in tissues, effector memory T cells circulate, and central memory T cells reside in secondary lymphoid organs.

Question 16

What are the three types of antigen presenting cells (APCs)?

Answer 16

Activated dendritic cells, activated macrophages, and activated B cells.

Question 17

What are the two ways a naive B cell can be activated?

Answer 17

T cell-dependent activation and T cell-independent activation.

Question 18

How does PD-1 contribute to T cell lethargy in inflamed tissues?

Answer 18

PD-1 binding to PD-L1 in inflamed tissues results in reduced T cell activity and promotes exhaustion.

Question 19

What is the difference between T cell-dependent and T cell-independent activation?

Answer 19

T cell-dependent activation requires help from T cells and co-stimulatory signals, while T cell-independent activation can occur without T cell involvement.

Question 20

How do Th2 helper T cells contribute to the immune response against parasites?

Answer 20

They release IL-4, IL-5, and IL-13 to stimulate class switching in B cells to IgE for parasite defense.

Question 21

What is the role of CD4 and CD8 co-receptors in T cell function?

Answer 21

CD4 is involved in helper T cell function (MHC II), while CD8 is involved in CTL function (MHC I).

Question 22

How do B cells undergo somatic hypermutation during maturation?

Answer 22

B cells mutate their antibody genes to increase affinity for antigens, allowing for improved immune responses.

Question 23

What is the process of receptor editing in B cells?

Answer 23

B cells with self-reactive BCRs can rearrange their light chain genes to avoid self-binding.

Question 24

How do encapsulated organisms affect B cell activation in the spleen?

Answer 24

Spleen can activate B cells independently of T cells via marginal zone B cells in response to polysaccharide antigens.

Question 25

What are the primary functions of Th1 helper T cells?

Answer 25

They promote cell-mediated immunity, activate macrophages, and stimulate B cell class switching to IgG3.

DC releases IL-12
Th1 realeases:
- TNF
- IFN-gramma
- IL-2

Question 26

Why is co-stimulation necessary for T cell activation?

Answer 26

Co-stimulation activates naive T cells and amplifies TCR signaling.
-CD40 and CD40L

Question 27

How do cytotoxic T lymphocytes (CTLs) recognize and kill infected cells?

Answer 27

CTLs recognize infected cells via MHC I presenting foreign peptides and kill them using perforin and granzyme B.

Question 28

What are the clinical implications of a deficiency in CD40 or CD40L?

Answer 28

Deficiency leads to absent T-dependent antibody responses and increased susceptibility to infections.

Question 29

What is the role of cytokines in the differentiation of T helper cells?

Answer 29

Cytokines influence the differentiation of naive T cells into specific subsets (Th1, Th2, Th17) based on the pathogen.