1-T Lymphocytes

Question 1

general characteristics

Answer 1

-subset of lymphocyte family with B cells and NK cells
-cannot be distinguished from B cells morphologically
-only recognize antigen with APC and MHC unlike B cells

Question 2

ontogeny

aka where they come from

Answer 2

1. prothymocytes from bone marrow
2. thymus for maturation
3. peripheral lymphoid organs
4. blood stream until directed for cell mediated immune response

Question 3

T helper lymphocytes aka CD4 subsets

Answer 3

1. TH1 = cell mediated immunity (macrophages, IgG syn)
2. TH2 = humoral immunity (mast cells, eosinophils, IgE syn)
3. TH17 = enhances inflammation
4. TFH = promote proliferating B cells/germinal centers in lymphoid organs

Question 4

cytotoxic T lymphocytes

Answer 4

aka CTLs/CD8
lyse virus infected cells

Question 5

regulatory T lymphocytes

Answer 5

aka CD4 or Treg cells

downregulate immunity

Question 6

T cell antigen receptor

Answer 6

sites for antigen peptide residue + MHC residue
-30,000 identical copies of TCR in T cell surface

Question 7

TCR structure

Answer 7

heterodimer of disulfide linked alpha/beta chains
-each chain has constant and variable region but only 1 antigen binding site

cytoplasmic tails not long enough to act as signal transducer across plasma membrane

Question 8

CD3

Answer 8

required for signal transduction of T cells so expressed on every T cell but dont have anything to do antigens

made of invariant polypeptides (1 gamma + 1 delta + 2 epsilon + 2 zeta)

phosphorylation site on cytoplasmic tail for signals

Question 9

co stimulatory molecules

TCR

Answer 9

1. CD28 on T cell binds B7 on APC
2. CD40L on T cell binds CD40 on APC
   B7 and CD40 expressed on all professional APCs

end goal to enhance T cell proliferation ‘build army before attacking antigen’

Question 10

CD4 accessory protein

Answer 10

transmembrane glycoprotein of single polypeptide on majority of mature T cells
-small quantities on surface of macrophages

most CD4 expressing lymphocytes are T helper cells

Question 11

CD4 function

Answer 11

1. cell adhesion
2. signal transduction
3. restricts T cell response to class II MHC

Question 12

CD8 accessory protein

Answer 12

homodimer or heterodimer with alpha/beta chains

most CD8 expressing lymphocytes are cytotoxic T lymphocytes (CTLs)

Question 13

CD8 functions

Answer 13

1. cell adhesion
2. signal transduction
3. restrict T cell resp to class I MHC

Question 14

signal transduction pathway

Answer 14

1. binding of TCR to MHC to initate activate T cells
2. early activation- PKC and other kinases activated to phos transcription factors
3. gene transcription- AP 1 initiates IL-2 cytokine production
4. mitosis- expand antigen specific clones to amplify immune response

Question 15

TH1 development

Answer 15

1. IL-12 from inflamm develop naive T cells
2. interferon gamma IFN-y directs toward cell mediated immunity with active macrophages and CTLs

-CTL differentation via CD4 helper T cells producing cytokines and enhancing APC ability to stimulate differentiation

IFN-y most potent activator of macrophages

Question 16

TH2 cell development

Answer 16

1. naive exposed to IL-4
2. direct immune resp toward IgE production for anti-parasite defense
3. produce IL4, IL5, IL13

if no inflammation then immune resp default to TH2

Question 17

TH17 cell development

Answer 17

1. naive exposed to IL-1, IL-6, TGF-beta from dendritic cells during anti microbial and inflamm
2. produce IL-17 and IL-22 to promote inflam

Question 18

regulation of TH1 and TH2

Answer 18

IFN-y from TH1 will inhibit TH2
IL4 and IL13 from TH2 inhibit TH1

antagonistic effect

Question 19

CTL activation

Answer 19

function to destroy intracellular microbes (virus, bacteria) or tumor cells or transplants
-part of cell mediated immunity by TH1

recognize endogenous peptides on class I MHC thru antigen recog with TCR and CD8

Question 20

CTL killing process

primary mechanism

Answer 20

1. target cell binding by recog class I MHC and antigen
2. CTL activation
3. lethal hit thru granule exocytosis, perforin makes pores for granzyme B to enter target and activate caspase pathway
4. disengagement from target cell
5. death via apoptosis

Question 21

CTL killing mechanism

secondary

Answer 21

1. bind CTL expressed Fas ligand to target cell Fas protein
2. activate caspases
3. apoptosis