Immunology Test 2 Chapter 5

Front 1

Thymus-dependent lymphocytes?

Back 1

1) aka T lymphocytes, Tcells
2) originate from bone marrow stem cells
3) migrate to mature in the thymus

Front 2

2 lineages of T cells develop in the thymus?

Back 2

1) a:B T cells
2) y:d T cells
a) thes lineages dev. In parallel from common precursor

Front 3

Developing thymocytes?

Back 3

1) Express other cell surface proteins
a) CD4 and CD8 gp.
(i) Which are essential for T cell response to cells presenting An.

Front 4

Once T cells leave thymus >?

Back 4

1) Secondary lymph tiss > return to lymph

Front 5

the thymus?

Back 5

1) Is a lymphoid organ in the upper anterior thorax (above heart)
a) Contains thymocytes embedded in the thymic stroma

Front 6

thymocytes?

Back 6

1) immature T cells

Front 7

thymic stroma?

Back 7

1) network of epithelial cells

Front 8

thymocytes + thymic stroma = ?

Back 8

1) outer close-packed cortex
2) inner, less dense, medulla

Front 9

Cortex?

Back 9

1) Epithelial cells arise form ectodermal cells
a) Consists of
(i) Immature thymphocytes
(ii) Branched cortical epithelial cells
(iii) A few macrophages

Front 10

Medulla?

Back 10

1) Epithelial cells derived from endodermal cells
a) Consists of
(i) Mature thymphocytes
(ii) Medullary epithelial cells
(iii) Dendritic cells
(iv) Macrophages.

Front 11

One fnx of the macrophages in both cortex & medulla?

Back 11

1) Is to remove the many thymocytes > fail to mature properly

Front 12

Hassall’s corpuscles?

Back 12

1) Char. Feature of medulla
2) Sites of cell destruction

Front 13

thymic anlage?

Back 13

1) ectodermal cells + endodermal cells
a) form rudimentary thymus
2) subsequently b/c colonized by cells from bone marrow

Front 14

DiGeorge’s Syndrome?

Back 14

1) Genetic disease
2) Thymus fails to develop,
a) T cells are absent,
b) Results in susceptibility to wide range of opportunistic infec.
3) Resembles SCID (severe combined immunodef disease.

Front 15

thymus activity?

Back 15

1) Most active – young
2) Atrophies w/ age
a) Degeneration complet by 30 years old.

Front 16

impairment of T cell immunity is not effected by?

Back 16

1) Reduced production of new T cells by thymus
2) Thymectomy (removal of thymus)

Front 17

maturation of thymocytes into mature T cells occurs?

Back 17

1) in distinct stages
a) marked by changes

Front 18

Stages marked by distinct changes?

Back 18

status of Tcell receptor genes
2) expression of the T cell receptor genes,
3) expression of the t cell receptor protein
4) production of the tcell surface fp essential for the receptors full fnx
a) such as CD4 & CD8 and CD3 complex

Front 19

“double-negative” thymocytes?

Back 19

1) immature thymocytes expressing neither CD4 nor CD8

Front 20

as double neg. thymocytes mature?

Back 20

1) 1st express the adhesion molecule CD44 then CD25

Front 21

CD44 and CD25?

Back 21

1) Component of the receptor for the cytokine interleukin-2 (IL-2).

Front 22

After expression of CD 44 decreases ?

Back 22

1) T cell receptor gene rearrangements commence.

Front 23

T cells have two lineages?

Back 23

1) expression of a:B receptor
2) expression of y:d receptor

Front 24

commitment to lineage?

Back 24

1) occurs as consequence of a race b/t the diff loci > productive rearrang.

Front 25

What is the first major difference b/t Bcells and Tcells?

Back 25

1) T cells stat to rearrange their B-, y-, and d-chain genes at about the same time.
2) B cells each type of Ig gene is rearranged in turn in a set order.

Front 26

Lineage commitment to a:B or y:d t cells is consequence of ?

Back 26

1) The order of successful gene rearangements

Front 27

T cell progenitors express?

Back 27

1) no t cell specific markers
2) they 1st express CD44 and CD25 cell surface gp.

Front 28

after expression of CD44 and CD 25?

Back 28

1) B-, y- and d- chain loci begin rearrangements.

Front 29

if the y- and d- genes are rearranged productively before the B gene?

Back 29

1) Appearance of y:d receptor on cell surface signals to Stop B-chain rearrang.
2) Cell commits to the y:d lineage

Front 30

what is the more common outcome?

Back 30

1) the B-chain gene rearrange productively before a fnx y:d receptor is made

Front 31

If B-chain gene rearrange productively before fnx y:d receptor?

Back 31

1) Pre-T-cell receptor
a) Signals to stop B-, y- and d- chain genes rearrang
b) And enter phase of proliferation

Front 32

after proliferation ?

Back 32

1) recom. Machinery is reactivated targeted to the a-chain locus (and the unproductive y-and d-chain genes.)

Front 33

What if y- and d-chain genes are rearranged before a-chain genes?

Back 33

1) Forms a y:d Tcell lineage.
2) This is minority

Front 34

If a-chain gene occurs first ?

Back 34

1) Leads to a:B cell receptor
a) Signals for a a:B T cell

Front 35

Production of a T-cell receptor B-chain leads to cessation of ?

Back 35

1) B-chain gne rearrangement
2) and to expression of CD4 & CD8

Front 36

similarity between T cell rearrangements and Ig rearrangements?

Back 36

1) rearrangements of a- & B- chain loci vs. Ig loci
a) Ig H-chain VS. Tcell B-chain
b) Ig L-chain VS. Tcell a-chain
c) RAG-1 and RAG-2 in both
d) Pre-Tcell receptor VS pre-Bcell receptor

Front 37

Ig H-chain VS. Tcell B-chain?

Back 37

1) contain V, D and J gene segments
2) rearranged first

Front 38

Ig L-chain VS. Tcell a-chain?

Back 38

1) No D segments
2) Rearranged second

Front 39

RAG-1 and RAG-2 in both?

Back 39

1) Gene rearrangement is preceded by small amounts of transcription from the gene segments to be recombined by expression of RAG genes

Front 40

Pre-Tcell receptor VS pre-Bcell receptor?

Back 40

1) Same function for both
a) Its appearance triggers the thymocyte to proliferate
(i) And to halt B-gene rearrangement.

Front 41

the T cell receptor B-chain genes rearrange first in?

Back 41

1) CD4- CD8- thymocytes (double negative)
a) That express CD25+ and CD44 low. On cell surface p.

Front 42

what genes are rearranged first? And produces?

Back 42

1) B-chain D to J
a) Then a V gene rearranges to DJ
2) B-chain protein

Front 43

B chain protein?

Back 43

1) Expressed w.in the cell and then
a) Appears in low levels on cell surface with surrogate a-chain (pTa) and CD3 chains ->Pre T cell preceptor

Front 44

Expression of pre-T cell receptor signals?

Back 44

1) stop B- rearrangement
2) cell proliferates

Front 45

after cell proliferation?

Back 45

1) CD4 and CD8 are expressed on cell surface

Front 46

expression of CD4 and CD8 on cell surface signals?

Back 46

1) a chain to rearrange

Front 47

when a fnxal a chain is produced?

Back 47

1) It pairs w/ the B-chain to form a a:B Tcell receptor.
2) Appears on surface with CD3 complex

Front 48

when Tcell receptor appears w/ CD3 complex?

Back 48

1) it is a double-positive thymocyte

Front 49

double positive thymocyte?

Back 49

1) expresses CD4, CD8 and the a:B Tcell receptor in assoc w/ CD3
2) it is ready to undergo selection

Front 50

what is a major difference between Ig Hchain and Tcell B-chain?

Back 50

1) Unproductively rearranged B-chain gene can be rescued by a second rearrangement
a) Because 2 sets of D(B)J(B) and C(B) gene segments are tandemly assoc w/ the V(B) gene segments.

Front 51

what do Ig L-chains have in common with T cell a-chains?

Back 51

1) They can undergo several successive gene rearrangements
a) Therefore has a greater chance of a successful rearrangement than the B locus

Front 52

How does the a-chain have a greater chance of success?

Back 52

1) The presence of many V(a) and over 50 J(a) gene segments,
a) Allows successive VJ(a) rearrangements to be tried

Front 53

successful rearrangement of one copy of the a-chain gene and cell surface expression of a fnxal a:B receptor does NOT?

Back 53

1) Prevent other copy of a-chain gene
2) Many T cells express 2 a-chains and have 2 diff. t cell receptors
a) Will be +/- selected later.

Front 54

Cells expressing particular y:d receptors arise first in?

Back 54

1) Embryonic development.

Front 55

the 1st T cells to emerger during embryonic development carry?

Back 55

1) y:d receptors

Front 56

1st wave of y:d T cells ?

Back 56

1) migrate specifically to the skin
a) called dendritic epidermal T cells (dETC)

Front 57

2nd wave of y:d T cells?

Back 57

1) Migrate to the epithelial layers of the reproductive tract.

Front 58

each wave is characterized by ?

Back 58

1) a distinctive y:d receptor that is carried by all the cells in a wave.

Front 59

How are early y:d T cells analogous to the B-1 cells that emerge from the bone marrow before birth?

Back 59

1) Timing of their emergence
2) Restricted use of particular gene segments
3) Lack of N nucleotides
4) Represent older, more primitive, and less specific components of the adaptive immune system

Front 60

later on in embryonic development T cells?

Back 60

1) Are produced continuously VS in waves
2) a:B cells now dominate (95%)
3) within y:d subpop.

Front 61

later on in embryonic development T cells within y:d subpop.?

Back 61

1) Receptors are more diverse
a) In number of alternative gene segments used
b) And in abundance of N-nucleotides additions
2) Found in peripheral lymphoid tissues VS solely in the epithelium of non.