T Cells

Question 1

Why is T cell maturation more complicated than B cell maturation?

Answer 1

it contains various T cell subsets that differ in receptor specificity and effector functions

Question 2

How do T cell receptors differ from B cell receptors?

Answer 2

no light & heavy chain, no isotype switching, not secreted, do NOT have Fc portions, NO affinity maturation, antigen does not cross-link the receptors, bind to peptides, dual specific

Question 3

What is the only function of T cell receptors?

Answer 3

T cell activation

Question 4

What do T cell receptors associate with?

Answer 4

CD3 complex

Question 5

What does the CD3 complex do?

Answer 5

signals events after the antigen-binding site has bound antigen, cell surface expression of T cell receptors

Question 6

How do TCR genes compare to immunoglobulin genes?

Answer 6

the same, V, D, & J segments rearrange to from complete genes with tremendous diversity

Question 7

What must T cell receptors recognize?

Answer 7

complex peptide & MHC, is specific for both (dual specificity)

Question 8

Compare & contrast CD4 & CD8.

Answer 8

both are co-receptors for alpha:beta T cell receptors, CD8 binds MHC class I molecules, CD4 binds MHC class II

Question 9

What do antigen-presenting cells do?

Answer 9

place of MHC:peptide expression, including dendritic cells, macrophages, and B cells; present costimulatory molecules

Question 10

What are the of y:S T Cells about?

Answer 10

NOT MHC-restricted, do NOT undergo positive selection, part of mucosal immunity, “primitive” cytotoxic cells and secrete cytokines when activated

Question 11

Where a:B T cells mature?

Answer 11

thymus, called thymocytes, cortex to corticomedullary junction to medulla

Question 12

Where do T cell precursors enter the thymus?

Answer 12

cortex

Question 13

What are stromal cells? what do they include?

Answer 13

resident cells in the thymus, epithelial cell, dendritic cells and macrophages

Question 14

What are double negative cells? double positive cells? single positive cells?

Answer 14

T cell precursors that enter thymus (do not express receptor or co-receptor), once receptors are acquired, lose coreceptor (functional)

Question 15

What happens if cells fail to express functional T cell receptors?

Answer 15

death

Question 16

What is positive selection?

Answer 16

immature T cells with receptors are given positive signal to allow for proliferation, those that don’t die, mediated by cortical epithelial cells causing T cells to become MHC restricted

Question 17

What is negative selection?

Answer 17

after positive selection, if T cell receptors bind well to self MHC & self antigens they could form autoimmune diseases so they are killed, mediated by dendritic cells and macrophages, is a form of deletion for immune self tolerance

Question 18

What is antigen processing?

Answer 18

series of proteolytic events to generate antigenic peptides and occurs inside APCs

Question 19

How are antigens outside APCs (exogenous antigens) cleaved?

Answer 19

proteases in endosomes and lysosomes, CD4 cells & class II molecules

Question 20

How are endogenous antigens cleaved?

Answer 20

in the cytosol by proteasomes in ER with peptide transporter TAP, CD8 cells class I cells

Question 21

Major Histocompatibility Complex (MHC) name in humans?

Answer 21

Human Leukocyte Antigens (HLA)

Question 22

How many genes are expressed?

Answer 22

multiple MHC class I & class II

Question 23

What does it mean that MHC classes are highly polymorphic?

Answer 23

different alleles are present for each gene, unrelated individuals express different MHC molecules

Question 24

What does it mean that MHC classes are allogenic antigens?

Answer 24

they impact transplantation

Question 25

Why is it important that polymorphism is present in MHC?

Answer 25

dictates what peptides mind MHC molecules and what antigens can be recognized by a:B T cells

Question 26

Where are MHC class I expressed?

Answer 26

all nucleated cells, NOT RBCs

Question 27

What is characteristic of B2microglobulin of MHC Class I?

Answer 27

it is NOT polymorphic and is the same for all MHC class I molecules

Question 28

What is the peptide-binding cleft or groove?

Answer 28

where antigenic peptides bind

Question 29

What expresses MHC Class II molecules?

Answer 29

“professional” antigen-presenting cells (macrophages, dendritic cells, B cells)

Question 30

What is unique about MHC Class I peptide binding groove?

Answer 30

both chains are polymorphic, one molecule can bind an array of peptides

Question 31

What are the 3 consequences of MHC restriction & polymorphism?

Answer 31

a:B T cells are required to interact physically with cells exposed to antigen (local response), T cell activation, some individuals are resistant to a pathogen

Question 32

How are CD8+ T cells and CD4+T Cells distinguished?

Answer 32

co-receptor expression, MHC restriction, and their effector functions

Question 33

What are the components of CD8+ T cell?

Answer 33

mainly cytotoxic T cells (CTL), granzymes help perforin cause apoptosis as in NK cells

Question 34

What are the components of CD4+ T cell?

Answer 34

mainly helper cells to regulate immune responses with cytokines, includes Th1 and Th2 subsets

Question 35

What is the CD4+ T cell subset Th1 composed of?

Answer 35

cell-mediated immunity and enhances inflammation; interferon-y and TNF-a activate macrophages, IL-2 stimulate proliferation of Th1, CTL and NK cells

Question 36

What is the CD4+ T cell subset Th2 composed of?

Answer 36

induces humoral immunity; IL-4 and IL-5 promote antibody production by B cells, deliver the costimulatory signal to B

Question 37

When do CD4+ T cells become Th1 or Th2?

Answer 37

after they exit the thymus, is dependent on cytokines produced by APC

Question 38

What induces Th1 and Th2 cells?

Answer 38

IL-12 & interferon-y induce Th1 cells

IL-4 induces Th2 cells