T cell activation

Question 1

Condition 1

Answer 1

T cells do not recognize free antigens. An antigen must be membrane bound(ex on a APC)
B cells can recognize free antigens

Question 2

Condition 2

Answer 2

T cells recognize only processed antigens
processing take place in APC
T cells recognize peptide sequence
B cells recognize the shape of an epitope

Question 3

Condition 3

Answer 3

The processed antigen must associate with another protein molecule, MHC molecules, present on the membrane of the cell (ex APC)

Question 4

What happens when Hepatic or Epithelial cells are infected?

Answer 4

These cells do not express MHC class II
Antibodies cannot penetrate cell

Question 5

CD4 on a T helper cell is a receptor for

Answer 5

Class II molecules on APC

Question 6

CD8 on a Tc cells is a receptor for

Answer 6

Class I molecules on target cells

Question 7

Condition 4

Answer 7

Antigen presenting cells secrete interleukin-1 (IL-1) or other factors, interleukin 12 (IL-12) which are necessary for activation of T cells

Question 8

Rules for T cell recognition

Answer 8

T cells do not recognize free floating antigens
Antigens must be properly presented to T cell by APCs
antigen must be processed
antigen must be membrane bound
processed antigen that is membrane bound must physically associate with MHC Class I or II

Question 9

Rules for T cell activation

Answer 9

TCR will now recognize this presented antigen (First signal)
Activation of T ells require second signal or co-stimulatory signals

Question 10

Co-stimulatory Cytokines secreted by APC that act on T cells include:

Answer 10

Th1 and Th2 differentiation cytokines

Question 11

Th1 differentiation Cytokines

Answer 11

IL-12-leads to a bias in clonal expansion of Th-1 type cells
IL-18
IL-27
(Th-1 cells are important in immunity against INTRAcellular infections and are also involved in inflammatory conditions)

Question 12

Th2 Differentiation cytokines

Answer 12

IL-4 and IL_10 inhibit Th1 and default response is generation of Th-2 response (EXTRAcellular)

Question 13

IL-4

Answer 13

promotes anitbodies
stimulates B cells
stimulates T helper2/Inhibits Th1

Question 14

IL-6

Answer 14

promotes fever
promotes B cell functions

Question 15

IL-5

Answer 15

eosinophil growth and activation factor
Stimulates B
important in mucosal immunity

Question 16

IL-10

Answer 16

Inhibits Th-1 responses
Promotes some Th2 and B cell function

Question 17

Th-1

Answer 17

IFNgamma
important in INTRAcellular infection
proinflammatory effects
blocks Th-2

Question 18

Th-2

Answer 18

IL-4
Important in EXTRAcellular infection
secrete cytokines that promote antibody-mediated immunity
blocks Th-1

Question 19

T precursor CD4+ can become

Answer 19

Th-1 polarized cells or Th-2 polarized cells

Question 20

If T precursor becomes Th-1 cells

Answer 20

they secrete IFNgamma which will suppress Th-2 cells (therefore favor Th-1 cells)

Question 21

If T precursor becomes Th-2

Answer 21

they secrete IL-4 which will inhibit Th-1 cells (therefore favors Th-2 type immunity)

Question 22

Th 17 cells

Answer 22

secrete IL-17
Physiological effects
protective in infections
recruits monocytes and neutrophils
upregulates pro-inflammatory chemokines and cytokines
Pathological effects
increased in autoimmune disease

Question 23

Regulation of Immune response by T regulatory Cells

Answer 23

regulatory cells are heterogenous cells that present in low percentages (1-7 lymphocytes)-powerful in suppressing immune responses

Question 24

Loss of regulatory cells

Answer 24

induce severe autoimmune disease

Question 25

Administration of Regulatory cells

Answer 25

Suppress autoimmune dieases

Question 26

Regulatory cells may be involved in

Answer 26

pregnancy: local immune suppression
allergy
burns, cancer, viral diease