#1 - Life of a T Cell: Forming and Educating the Army

Question 1

List the possible functions of the T cell (5)

Answer 1

1) Direct killing of infected cells
2) Release of cytokines that will recruit granulocytes, macrophages and monocytes
3) Assistance to B cells and the production of antibodies
4) Direct killing of self cells (pathogenic autoimmunity)
5) Vaccine response

Question 2

when forming a new T cell, what is the order of chain construction? what domains contribute to the construction of the subunits?

Answer 2

Beta chain is assembled: this leads to pre-TCR, then alpha chain joins
beta chains are composed of all three (V,D,J) domains
alpha chains are composed of only V and J domains

Question 3

what does “SP” refer to in CD4 SP

Answer 3

single positive

Question 4

what type of HLA molecule produces an iNK T cell?

Answer 4

CD1d (glycolipid associated)

Question 5

what are the subunits of the CD3 complex?

Answer 5

two epsilon, one gamma, one delta, two zeta

Question 6

what is the entirely different subset of T cells called (apart from the alpha/beta T cells?)

Answer 6

gamma/delta - not otherwise tested

Question 7

what three types of cells can be found in the thymus? (two others in trace amounts) what type of cell is conspicuously absent?

Answer 7

epithelial cells, mesenchymal cells, bone-marrow derived hematopoetic cells that develop into thymocytes; macrophages and dendritic cells in “small amounts”; B cells are conspicuously absent

Question 8

in an SEM of the thymus, what types of cells are the tennis balls and what type make up the spindles?

Answer 8

T cells are balls, epithelial cells are the spindle

Question 9

what determines the developmental fate of a T cell?

Answer 9

the signals that it receives from a peptide/HLA complex

Question 10

what are the four alpha/beta T cell lineages? what HLA leads to these lineages? (what are the classes of the ligands bound to these HLA?)

Answer 10

CD4, CD4 Treg, iNK, CD8
HLA II, HLA II, CD1d, HLA I
(peptide, peptide, glycolipid, peptide)

Question 11

the majority of cells in the thymus express what receptor?

Answer 11

double positive, meaning that they express both CD4 and CD8 receptors and have not been exposed to HLA I or II

Question 12

where will you find no double positive cells?

Answer 12

in the lymph nodes

Question 13

what types of cells show up as double negative cells in a scatterplot of CD4+ vs. CD8+ cells in the lymph nodes?

Answer 13

B cells

Question 14

what is the first step in the formation of a T cell?

Answer 14

arrival of a stem cell in the thymus and the creation of a DN (double negative) cell

Question 15

what cytokine acts as a growth factor that enables DN cells to mature into DP cells?

Answer 15

IL-7

Question 16

what critical event happens in between the DN2 and DN3 substages? if this fails, what happens to the T cell?

Answer 16

beta gene rearrangement; in the event of failure, the T cell is developmentally arrested and eventually will die unless the problem is fixed

Question 17

assuming successful formation of the TCR, what coreceptor molecules are expressed in the next stage of development? What is this stage of development called?

Answer 17

CD4 and CD8 coreceptors. Double positive stage (DP)

Question 18

when do NK (note: NOT iNK) cells branch off on their developmental pathway?

Answer 18

prior to any VDJ rearrangements (prior to DN2-3)

Question 19

what are the three developmental fates that can happen to a T cell (CD4 or CD8)

Answer 19

positive selection (weak handshake); negative selection (strong handshake); neglect (no handshake)

Question 20

which of the three fates do most T cells undergo?

Answer 20

neglect

Question 21

where do the peptide/HLA recognition sequences come from?

Answer 21

they are all “self” made, not foreign body

Question 22

why does the system prefer the weak “handshake” to the strong one?

Answer 22

because too strong of a reaction to a “Self” peptide is likely to initiate an autoimmune reaction

Question 23

what is the function of the AIRE protein?

Answer 23

to force thymic expression of tissue antigens that would not otherwise be in the thymus

Question 24

what is used as a marker for the detection of T cell production?

Answer 24

TRECs

Question 25

what is required for newly minted T cells to egress into the blood? what drug blocks this activity?

Answer 25

sphingosine 1 phosphate receptor (S1P1); FY720 (fingolimod)