Antigen presentation and T lymphocytes

Question 1

What are some examples of APCs and their respective locations?

Answer 1

Dendritic cells - skin/mucosa
Macrophages - skin/mucosa
B cells - 2° lymphoid organs

Question 2

How do APCs process and present antigens?

Answer 2

Major Histocompatability Complexes
Class I - all cells:
-endogenous antigen = CD8+
-invariant chain/CLIP
-HLA-DM
Class II - APCs:
-exogenous antigen = CD4+
-proteasome
-PLC (TAP, tapasin, Erp57, calreituclin)

Question 3

What is the structure of MHC I?

Answer 3

heterodimer

3 α chains + 1 β2 microglobulin

Question 4

What is the structure of MHC II?

Answer 4

heterodimer

2 α chains + 2β chains

Question 5

How are MHC molecules distributed?

Answer 5

Class I
-All cells
-endogenous antigens presented to CD8+
Class II
-APCs
-exogenous antigens presented to CD4+

Question 6

What is the importance of antigen presenting cells in the induction of T lymphocytes?

Answer 6

APCs provide activation signal - activated T cells acquire effector functions
MHC bound peptide interacts with T cell receptors
Co-stimulation with CD80/86 and CD28
Cytokine stimulation neccessary to mature and develop

Question 7

Where do T cells originate?

Answer 7

Bone marrow -> thymus

Question 8

What are the functions of the T lymphocyte subsets?

Answer 8

Cytotoxic T cells - kill virally infected or transformed cells
Th1 - Intracellular infection
Th2 - Allergy
Th17 - inflammation, bacterial and fungal infection
Treg-regulation of effector T cell function

Question 9

How can lymphocyte responses be regulated?

Answer 9

Cytokines influence differentiation and development as a response targeted to organism

Question 10

Why is lymphocyte regulation important?

Answer 10

Prevent responses against self ( central and peripheral tolerance) and to avoid tissue damage