T cell Responses and Cell-Mediated Immunity

Question 1

where do T-cells mature?

Answer 1

thymus

Question 2

what are immature t-cells called?

Answer 2

thymocytes

Question 3

describe thymic selection

Answer 3

TCRs position their CDR regions (hypervariable region with peptide specificity) so that binding occurs d/t the gestalt molecular signature of the MHC plus peptide

positive selection occurs first. t-cells that recognize a peptide:MHC complex and bind weakly are allowed to survive. most cells die in this stage

negative selection: t-cells that recognize a MHC:peptide complex and bind too tightly are eliminated b/c they cause autoimmunity

Question 4

where do positive and negative t-cell selection occur specifically?

Answer 4

thymus

positive- thymic epithelial cells
negative- thymic medulla or medulla/cortical junction

Question 5

autoimmune regulator (AIRE)

Answer 5

a transcriptional regulator that allows expression of non thymic genes to provide peptides for negative selection

Question 6

immunotolerance

Answer 6

your immune system will not attack “self” antigens- this is tolerance

there are two types: central and peripheral

central- removal of autoreactive t-cells during development in the thymus via negative selection

peripheral- several mechanisms

1. ignorance- they cannot reach the area where their antigen resides (testes)
2. anergy- recognition of an autoantigen does not usually occur with a costimulator, which actually leads to cell shutdown
3. Regulatory t-cells- suppress autoreactive cells

Question 7

what intracellular compartment do CD8 t-cells target?

Answer 7

cytosolic

Question 8

How do CTLs kill?

Answer 8

perforin- destroys membrane integrity

granzymes- activate capsases

Fas-L- apoptotic membrane receptor

Question 9

describe Th1 cells

Answer 9

CD4 cells that develop in response to IL-12 and mediate inflammatory responses by activating macrophages. they also secrete INF-g, TNF, IL3, and GMCSF

Question 10

describe Th2 cells

Answer 10

CD4 cells that develop in response to IL-4 that handle parasitic infections, as well as activating B cells and antibody responses. they secrete IL4, 5, and 13

they contain CD40L on their cells which interacts with CD40 on B-cells. IL-4 causes the release of IgE, which acts on mast cells to produce more IL-4. IL-5 induces eosinophils for combating helminths

Question 11

describe Th17 cells

Answer 11

CD4 cells that develop in response to IL17. they recruit neutrophils and secrete IL-22 and IL-17

Question 12

what does TNF release via Th1 cells do?

Answer 12

changes endothelial properties to recruit other leukocytes

Question 13

Th1 cells inhibit Th2 cells via IFN-g

Answer 13

ok

Question 14

Tregs

Answer 14

CD4 cells that suppress the immune response, inflammation, and support peripheral tolerance. they act in an unknown contact dependent manner and secrete IL-10 and TGFbeta.

Question 15

Foxp3

Answer 15

a gene vital to regulator t cell function. knock out can cause autoimmunity

Question 16

high endothelial venules

Answer 16

the area in lymph nodes where lymphocytes can enter

Question 17

how do lymphocytes exit the bloodstream

Answer 17

they interact with selectins (via their addressins) to slow down their rolling, then integrins get upregulated via cytokines that cause stronger attachments to be made (ICAM-1, LFA-1). they then move across the endothelial barrier

Question 18

what is unique about MALT lymphocyte migration

Answer 18

activated lymphocytes in one MALT can leave, enter the bloodstream, and go to another MALT to provide protection

Question 19

differentiate between effector and central memory t cells

Answer 19

both remain after an initial response to an antigen;

effector cells do no proliferate as much upon second exposure but make more cytokines. central proliferate more rapidly