Week 2 T cells

Question 1

The thymus is a primary or secondary lymphoid organ?

Answer 1

Primary lymphoid organ

Question 2

What important types of cells are found in the cortex of the thymus?

Answer 2

Cortical epithelial cells, thymocytes (developing lymphocytes)

Question 3

What important types of cells are found in the medulla of the thymus?

Answer 3

Medullary epithelial cells, dendritic cells and macrophages

Question 4

How many antigen-binding sites do T cell receptors have?

Answer 4

Just 1

Question 5

What co-receptor on the T cell surface indicates the rearangement of TCR alpha and beta chains?

Answer 5

CD3

Question 6

CD4+ T cells are what type? CD8+?

Answer 6

CD4 = Helper T cells, CD 8 = Cytotoxic T cells

Question 7

What are the stages between stem cells and naive mature T cells?

Answer 7

Stem cell -> Pro-T (double negative, neither CD4 or CD8) -> Pre-T -> Double positive (CD4 + CD8) -> single positive (CD4 or CD8) -> naive mature T cell

Question 8

What class of MHC are CD4+ cells restricted to? CD8+?

Answer 8

CD4+ -> class II restriction, CD8+ -> class I restriction

Question 9

What is the role of the zeta chain in T cell receptor signaling?

Answer 9

Zeta chain contains the item sequence which will be phosphorylated, mediating the recruitment of other molecules. The MAP-kinase cascade will be activated, leading to synthesis and activation of transcription factors

Question 10

Signals induced by TCR complex activation: TCR -> ?, CD28 -> ?, Cytokines -> ?

Answer 10

TCR -> activation, CD28 -> costimulation, Cytokines -> differentiation

Question 11

What does MHC stand for?

Answer 11

Major Histocompatability Complex

Question 12

Which cells have MHC class I? Which have class II?

Answer 12

MHC Class I: every nucleated cell, Class II: antigen-presenting cells

Question 13

What are the most important antigen-presenting cells? What are some less important ones?

Answer 13

Dendritic cells are most important for antigen-presentation, macrophages less so, and neutrophils are most important for phagocytosis but also carry antigen-presentation function. B cells also perform antigen-presentation

Question 14

Which subunit of Class I MHC molecules binds to CD8+ T cell receptors?

Answer 14

alpha 3

Question 15

Which subunit of Class II MHC molecules binds to CD4+ T cell receptors?

Answer 15

beta 2

Question 16

Can T cells ever be activated without MHC recognition?

Answer 16

No! There is MHC restriction

Question 17

How are antigens presented by MHC class I?

Answer 17

Cytosolic proteins and defective ribosomal products are degraded to peptide fragments, and TAP (transporters associated with antigen processing) delivers those peptides to the ER. The peptide binds the MHC class I molecule and completes its folding, then the MHC class I molecule is exported to the cell membrane

Question 18

How are antigens presented by MHC class II molecules?

Answer 18

A foreign antigen is endocytosed, then degraded into peptide fragments. Vesicles containing peptides fuse w/ vesicles containing MHC class II molecules

Question 19

If an antigen enters the bloodstream, where will antigen-presenting cells likely capture it?

Answer 19

In the spleen

Question 20

What do Helper T cell type 1 do?

Answer 20

Recognize complex of bacterial peptides with MHC class II and release cytokines which activate macrophages, as well as B cells and neutrophils

Question 21

What do Helper T cell type 2 do?

Answer 21

Recognize complex of antigenic peptide, including multicellular parasites, with MHC class II and release cytokines that lead to activation of B cells into plasma cells

Question 22

What does thymus-dependent activation mean?

Answer 22

How B cells usually cannot be activated alone, but only with the help of helper T cells

Question 23

What type of antigens are CD8+ T cells particularly good for?

Answer 23

Virus-infected cells

Question 24

What effect do the two types of helper T cells have on each other?

Answer 24

They inhibit each other

Question 25

How to cytotoxic T cells cause apoptosis of target cells?

Answer 25

Granzymes and perforins are exocytosed by the T cell and then endocytosed by the target cell, which then activate apoptotic pathways

Question 26

What percentage of the mononuclear cells in the blood/spleen are natural killer cells?

Answer 26

5 to 20%

Question 27

What do the inhibitory receptors of natural killer cells bind to?

Answer 27

MHC class I molecules. NK cells will kill cells without MHC I.

Question 28

What activates natural killer cells?

Answer 28

Fc-receptors, NKG2D. If there is no MHC I on the surface of a cell, NK cells will kill it

Question 29

What is DiGeorge syndrome?

Answer 29

congenital malformation affecting development of thymus, leading to T cell deficiency

Question 30

What is Bare lymphocyte syndrome?

Answer 30

Lack of MHC class II expression, so defective antigen presentation to T cells

Question 31

What cells are infected by HIV?

Answer 31

CD4+ T cells, macrophages, dendrites