Exam #3

Question 1

Vladimir Badovinac & John Harty

Answer 1

Death of effector T cells is independant of clearance of infection

Question 2

Sue Kaech & Rafi Ahmed

Answer 2

Memory Cells are present during effector phase of T cell response and can be definied by expression of IL–7R chain

Question 3

Joe Sun & Mike Bevan

Answer 3

CD8 T cells that are primed without CD4 T cells don’t have memory. Possible mechanism is that these cells have proliferated more and have then died?

Question 4

Th1 Cells

Answer 4

Intracellular pathogens, Macrophages,
cytokines affecting differentiation IL-12 & IFN-g,
STAT pathway is STAT1 (IL-12) and STAT4 (IFN-g),
Transcription factor is T-bet,
Cytokines produced by CD4 helper cell: IFN-g
B cell isotypes induced: IgGa, IgG3
Beneficial effects: Macrophage activation, clearence of intracellular pathogens
Harmful effects: Systemic pathology

Question 5

Th2 Cells

Answer 5

Extracellular parasites
Eosinophils, basophils, mast cells
Cytokines affecting differentiation: IL-4
STAT pathwy: STAT6
Transcription factor: GATA3
Cytokines produced: IL-4, IL-5, IL-13,
B cell isotypes induced: IgE, IgG1
Beneficial effects: Eosinophil, basophil, and mast cell activation, clearence of extracellular pathogens,
Harmful effects: Allergies and asthma

Question 6

Th17

Answer 6

Extracellular bacteria/fungi
Neutrophils
Cytokines affecting differentiation: IL-6, IL-23
STAT pathway: STAT3
Transcription factor RORgt
Cytokines produced: IL-17, IL-6
B cell isotypes induced: IgA, IgG2b
Benefits: Neutrophil activation, clearence of extracellular bacteria/fungi
Harful effects: Autoimmunity and Inflamation

Question 7

Treg

Answer 7

Activated by ongoing immune response
Cytokines affecting differentiaion: IL-2
STAT pathway +: STAT5
Transcription factor: FOXP3
Cytokines produced: IL-10, TGF-b
Does not induce B cell isotypes
Inhibits overaction of other T cells

Question 8

What are the 3 ways AID induced mutation can be repaired?

Answer 8

1. Replication –> GC pair and AT pair
2. Repair using MSH2/6 –> GC and mutates nearby AT segments
3. Cleavage by UNG to abasic site and repair of abasic site by REV1 –> Cleave U and replaces with a random base

Question 9

IFNy

Answer 9

Produced in response to systemic infection, signals through STAT1, induces Igy S-transcripts and IgG. Results in systemic antibodies

Question 10

TGFb

Answer 10

Produced in response to T cells in mucosal lymphoid tissue, signals through smad 2/3, induces Iga S-transcripts and IgA. Results in mucosal antibodies

Question 11

IL-4

Answer 11

Produced in response to pathogens at epithelial surface, signals through STAT3/6, Induces Ige S transcripts IgE, Allows mast cells to enhance immunity at epithelial surfaces

Question 12

Name 4 routes for antigen to be taken up for presentation to T cells

Answer 12

1. receptor mediated phagocytosis (LN resident DC)
2. macro-pinocytosis (LN resident DC)
3. viral infection (any DC)
4. Cross presentation after phagocytic or macropinocytic uptake (dv103+ DC)

Question 13

CD103+ DC

Answer 13

Migratory DC that is good at Ag cross-presenting and starting a T cell response

Question 14

Plasmacytoid

Answer 14

LN Resident DC that is the main source of Type I IFN

Question 15

IgM

Answer 15

antibody whose main function is complement activation and initial killing of microbes

Question 16

IgG

Answer 16

Main serum antibody ( 4 subtypes) main function is neutralization, opsonization for phagocytosis, NK cell activation via Fc receptors, complement activation

Question 17

IgA

Answer 17

Main mucosal antibody (2 subtypes) Main function if neutralization in mucosa

Question 18

IgE

Answer 18

Epithelial surface antibody that binds to Fc receptors on mast cells and basophils

Question 19

FRN

Answer 19

Follicular Reticular Network in LN that free Ag ride in, T cells and DC cells travel on, ect

Question 20

Transcytosis

Answer 20

The process of going through a macrophage to another side

Question 21

AID

Answer 21

Acivation Induced Deaminase. Triggered by CD40 signalling adn converts C to U.

Question 22

CD40 signalling

Answer 22

B cells activated by agiC3b or BCR crosslinking upregulate CD40. T cells activated by DC express CD40L and migrate to B zone. Signalling gets full activation for both T and B cells.

WIthout this B cell forms primary foci for short lived IgM response

Question 23

Cross-linking

Answer 23

T cell independant. Cross-linking of BCR and CR2. Occurs due to multipble Ags and iC3b on microbial surfaces or FDC

Question 24

What are the steps for a lymphocyte to enter the LN via HEV

Answer 24

Rolling: Selectins such as L-selectin (aka CD62L)
Activation: Chemokines such as CCL21
Adhesion (makes high affinity): Integrins suchas LFA-1
Diapedesis: chemokines such as CL21 and CXL12

Question 25

L-selectin (aka CD62)

Answer 25

expressed on all naive T cells, for rolling stage of entrance to LN via HEV

Question 26

LFA-1

Answer 26

expressed on naive cells but upregulated by inflammatory cytokines to increase entry during LN inflammation caught by CCR7RExpressed by T cells to enter lymph node, then replaced by S1P1 receptor to migrate towards efferent LN
(activation increases CCR7 inatead of S1P1 receptor

Question 27

How do migratory DC enter LN?

Answer 27

Afferent lymphatics, slip and slide

Question 28

P- Selectin

Answer 28

Caught by CCR9 and goes to gut with integrin a4b7

Question 29

What are the 3 signals of T cell activation?

Answer 29

TCR -> MHC:Ag binding
Costimulatory protein binding ligand on DC
Cytokine signal (ex IL-2 (for proliferation), IL-12, TFGb) *May be replaced by strong MHC:Ag binding and Costimulatory proteins binding to ligand on DC`

Question 30

What is the purpose of TCR co-receptors?

Answer 30

They stabilizze TCR:MHC binding and bring associated protein kintase (PTK) to the TCR

Question 31

E-selectin

Answer 31

Caught by CCR4 and goes to skin. Uses LFA-1 and a4ba integrins