11: T Cell Mediated Immunity

Question 1

IL-2

Answer 1

An autocrine survival signal for T cells

Question 2

IL-2RByc

Answer 2

IL-2 receptor constitutively expressed on mature, naive T cells with low affinity

Question 3

What happens to the IL-2RByc receptor upon T cell activation

Answer 3

Upregulation of CD25, the a chain of IL-2R -> creates IL-2RaBy receptor with high affinity

Question 4

What cell type always expresses CD25?

Answer 4

Tregs

Question 5

Trapping naive T cells in LN

Answer 5

1. newly activated T cell expresses CD69 -> binds naive T cell S1PR -> naive T cell sequesters S1PR
2. Without S1PR, T cells cant migrate (bc binding S1P in blood/lymph is what helps them migrate)
3. This ensures activated T cell has time to provide help to other lymphocytes
4. Within 5 days, activated effector cells migrate to periphery

Question 6

Five major functions of IFN-y

Answer 6

1. Stimulates macrophages
2. IgG class switching
3. Expression of HLA class II Ag presentation
4. Upregulation of CD80 (B7)
5. Inhibits Th2 and Th17 production

Question 7

What happens if Th2 is predominant in intracellular microbe response?

Answer 7

Poor disease outcomes

Question 8

Explain classical macrophage activation

Answer 8

Th1 cell migrates to infection -> samples Ags presented by macrophages -> immune synapse between Th cell and macrophage fully activates macrophage to become a better killer

Question 9

What do IL-4, IL-5, and IL-13 do from Th2 cells

Answer 9

Inhibit Th1 development

Question 10

IL-5 function

Answer 10

Increases eosinophil migration/activation

Question 11

IL-13 function

Answer 11

Increases mucus production in epithelium

Question 12

What do both IL-17 and IL-22 do?

Answer 12

Stimulate defensin production

Question 13

IL-17 function

Answer 13

Pro-inflammatory; recruits pro-inflammatory leukocytes

Question 14

IL-22 function

Answer 14

Protective; promotes regeneration in epithelial barrier to prevent breaks in skin

Question 15

What specific diseases do Th17 cells play a role in?

Answer 15

RA, MS, IBD, integument pathology, cancers (breast, lung)

Question 16

What two things are constitutively expressed on Tregs?

Answer 16

CTLA-4, CD25

Question 17

What does CTLA-4 bind to?

Answer 17

CD80 (B7) on APCs; with a higher affinity than CD28

Question 18

IL-21

Answer 18

B cell survival, clonal expansion, plasma cell differentiation

Question 19

Similarities between NK cells and CTLs

Answer 19

1. Both kill tumor-transformed cells and virus infected cells
2. Both use granzymes/perforin or Fas/FasL induction of apoptosis

Question 20

Differences between NK cell and CTL killing

Answer 20

CTL: notices altered peptide on class I HLA
NK cell: notices decreased display of class I HLA

Question 21

Where are y/S T cells found?

Answer 21

Epithelial boundaries, especially gut

Question 22

y/S T cell Ag recognition

Answer 22

Recognizes a limited diversity of peptides, but can also recognize some non-protein Ags because they are NOT HLA restricted

Question 23

What anti-apoptotic protein is expressed by memory T and B cells

Answer 23

Bcl-2

Question 24

What type of signaling domain does PD-1 contain?

Answer 24

ITIM

Question 25

Do memory CD4 and CD8 cells require reactivating?

Answer 25

Yes

Question 26

Which two cytokines are imperative for memory T cell survival?

Answer 26

IL-7, IL_15

Question 27

What happens when T cells express increased amounts of PD-1 and CTLA-4

Answer 27

They become exhausted