Adaptive Immunity: T cells Flashcards
MHC class \_\_\_ expressed on all nucleated cells Activates \_\_\_ T cells --> eliminate \_\_\_\_ pathogens
Class 1
CD8+
Intracellular pathogens
Calnexin
Binds to alpha chains of MHC class 1 in ER until Beta 2
Calreticulin, ERp57
chaperone proteins that bind to MHC class 1 in ER after calnexin releases it
TAP complex
Translocate peptide to ER for MHC class 1 loading Binds to MHC by tapasin
US6 and ICP47
Inhibition of MHC class 1 Expression: block antigen presentation by preventing peptide movement through TAP peptide transporter
E19
Inhibition of MHC class 1 Expression: compete and inhibit peptide loading onto MHC class 1 proteins
mK3
Inhibition of MHC class 1 Expression: mark MHC class 1 for degradation through ubiquitin
MHC class \_\_\_ expressed on APC Activates \_\_\_ T cells --> eliminate \_\_\_\_ pathogens
Class 2
CD4+
extracellular
HLA-DM
Binds to MHC to release CLIP fragment –> antigen peptide binds to MHC
Bare Lymphocyte Disorder Type 2
Defect in one of the transcription factors needed for MHC class II expression --> reduced number of activated CD4 T cells Death by 10 y/o due to severe infection
Bare Lymphocyte Disorder Type 1
Defect in expression of TAP1, TAP2 or Tapasin –> Don’t activate CD8+ T cells
Sensitivity t bacterial and parasitic infections later in life
Can use NK cells to fight viral infection but not efficient
DC licensing
dendritic cels need to be activated by CD4 T cells to cross present
Cross presentation
Dendritic cells: Present extracellular ligands on MHC class I Present intracellular ligands on MHC class II
MHC class 1 gene loci
HLA A, B, C
MHC class 2 gene loci
DP, DQ, DR
MHC class 3 gene loci code for ____
complement factors, cytokines
What stage does lineage bias occur for T cell development?
DN1
What stage does commitment to T cell during development occur?
DN2
When does beta chain rearrangement occur in T cell development?
DN3
When does alpha chain rearrangement occur in T cell development?
Double positive
Notch1
Cell surface receptor that determines T cell or B cell fate
TCR alpha chain gene
multiple copies of V and J regions + 1 copy of constant region –> V+J+ 1 constant
TCR beta chain gene
multiple copies of V, D and J regions + 2 copies of constant region –> V+D+1 constant
Recombination signal sequence (RSS)
TCR variable region rearrangment:
Surrounds each V, D and J region
12/23 Rule
Spacing of 23 and 12 bp of RSS
RAG1 and RAG2
TCR variable region rearrangment:
enzymes that recognize RSS sequence –> catalyze cleavage of RSS –> form closed DNA hairpin loop
Ku70/Ku80 proteins
Joining of cleaved DNA during TCR recombination:
Bind coding joint and signal joint
DNA ligase IV:XRCC4
Joining of cleaved DNA during TCR recombination:
Recruited by Ku70/Ku80 –> ligate DNA ends
DNA-PK and artemis
Joining of cleaved DNA during TCR recombination:
Recruited by Ku70/Ku80 –> open hairpin loop –> then released
TdT
Joining of cleaved DNA during TCR recombination:
Recruited by Ku70/Ku80 –> adds random basepairs to coding joint –> then released
Combinatorial diversity
V, D and J regions randomly recombined
Junctional diversity
V, D and J regions are recombined using random number of nucleotides
Immature T cell leukemia
Inappropriate expression of pre-TCR alpha chain
CDR1 and CDR2
Complementarity Determining Regions in variable region
Interact w/ MHC –> don’t want too much variation
Genomically encoded by V regions
CDR3
Complementarity Determining Regions in variable region
Interact w/ peptide –> needs a lot of variation
Encoded by recombination of V, D and J
CD4 binds _____
CD4 expressed on ____
MHC Class II
T helper cells
CD8 binds _____
CD8 expressed on _____
MHC Class I
Cytotoxic T cells
CD4 and CD8 interact w/ ______ region on MHC
invariant
ITAMs
Immune-tyrosine based activation motifs
On CD3 gamma, delta, epsilon, TCR zeta chains of TCR
Lck
Kinase that phosphorylates tyrosine on ITAMs on TCR –> initiates intracellular signaling
Dragged to TCR site of binding by CD4
ZAP-70
Recruited to phosphorylated ITAMs
Gets phosphorylated by Lck –> activated ZAP-70 phosphorylates adaptor protein LAT
PLC-gamma
Phospholipase C that cleaves phosphatidyl inositol 4,5 phosphate into DAG and IP3
Diacylglycerol (DAG)
second messenger that activates PKC –> transcription
Inositol 1,4,5 phosphate (IP3)
Second messenger –> signal Ca++ influx
SLP-76
Binds LAT –> recruit tyrosine kinase ITK –> phosphorylates PLC-gamma 1
Phosphatidyl inositol 3 kinase (PI3K)
phosphorylates PI on 3rd position –> forms PIP3 –> binds to proteins w/ pleckstrin homology domains
Akt
Serine/threonine kinase activated by PI3K –> regulates T cell survival
Guanine nucleotide exchange factor (GEF)
Recruited to LAT –> stimulate G proteins –> induce kinase cascade –> –> induced transcription factors
Ras/MAP kinase pathway
Ex kinase cascade
Activated LAT –> recruit GEF –> stimulate Ras –> induce Raf –> activate MEK –> ErK –> –> transcription factors
Calmodulin
activated by Ca2+ influx activated by PLC-gamma –> activate phosphatase calcineurin –> dephosphorylates NFAT –> activated NFAT –> translocate to nucleus
Calcineurin
target for large class of immunosuppressant Activates NFAT in T cells --> transcription factor
IKK complex
Classical pathway: DAG activates PKC –> activates IKK complex –> phosphorylates inhibitory protein I-kB –> degraded by proteasome –> release NF-kB –> translocate to nucleus –> gene transcription
p100
Alternative pathway: Activation of IKK –> phosphorylation and partial degradation of p100 –> formation of p52 –> facilitate translocation of RelB to nucleus –> gene transcription
Vav1
Recruited by LAT –> VAV1 –> Rac/CDC42 and WASp –> activates Arp2/3 complex –> regulate actin branching for formation of phyllopodia and lamellipodia in T cells
WASp
Activates Arp2/3 complex
Arp2/3 complex
regulate actin branching for formation of phyllopodia and lamellipodia in T cells
CD62L
High expression of CD62L on HEV epithelial cells causes T cells to go to lymph node
Sphingosine 1-Phosphate (S1P) Receptor
Expressed on T cells, made consistently on T cells
Activated when high conc. of S1P in blood bind –> cause T cells to move to lymph node –> S1P degraded
High expression when in lymph, low expression when in blood
CCR7
Drives maturation of DC
Expressed on DC when it recognizes a pathogen –> follows gradient of CCL19 and CCL21 –> migrate to lymphatics to T cells –> becomes mature DC –> activates T-cell
CCL19 and CCL21
Gradient produced at T cell zone by stromal cells that DC follow to activate T cells
B7-1 and B7-2 ( CD80, CD86)
Expressed on mature APC. Ligand for CD28 expressed on naive CD4 and CD8 T cells
CD28
Always expressed on CD4 and CD8 T cells. Receptor for B7-1 and B7-2 on mature APC.
Necessary for activating naive T cells
CD40L (CD56)
Expressed on T cells when co-activation of TCR and CD28 occurs –> Activate CD40 on APC –> increase ligands for second wave of costimulatory receptors
IL-2
Principle cytokine that drives differentiation and expansion of T-cells
CD69
Promotes S1P receptor degradation
Upregulated after T cell activation
Binds to S1P receptor w/o activation –> keep T cell in lymph
TNF and IL-1
Made by activated tissue macrophages and mast cells –> activate endothelium to express E/P selectins, chemoines, ICAM –> attract T cell to site of infection
VLA4
Expressed by activated T cells –> adhesion, trasmigration, migration of T cell to site of infection
TH1 cell
Produce _____ to activate ____ transcription factor, which produces _____ which activates _____
Respond to intracellular pathogens IL-12, IFN gamma T-bet IFN gamma, TNF macrophage activation, inflammation
TH2 cell
Produce _____ to activate ____ transcription factor, which produces _____ which activates _____
Respond to mucosal surface pathogens and big things IL-4 GATA3 IL4, 5, 13 allergic and helmith response
TH17 cell
Produce _____ to activate ____ transcription factor, which produces _____ which activates _____
Respond to extracellular small things (bacteria) IL-6, TGF-beta ROR gamma t IL-17A, IL-17F, IL-22 inflammation, neutrophil activation
IL-4
Produced by TH2 CD4 T cell
B cells switch to IgG and IgE
Alternative activation of macrophages
IL-13
Produced by TH2 CD4 T cell
Promotes mucus secretion and peristalsis
IL-5
Produced by TH2 CD4 T cell Activate eosinophiles and B cell class switching to IgA subtypes
IL10 + IL-4
Produced by TH2 CD4 T cell
Activate macrophage
IL-17
Produced by TH17 CD4 T cell
Recruits/activates neutrophils, enhances production of epithelial cell to produce anti-microbial peptides
IL-22
Produced by TH17 CD4 T cell
Induces keratinocytes to produce antimicrobial agents, promote epidermal hyperplasia
IL-21
stimulate activation of CD8 T cells , B cell class switching, NK and NK T cell differentiation, CXCL8 release from APCs
CCL20
Produced by TH17 CD4 T cell
regulates recruitment of TH17 cells to inflamed tissues
Fas/FasL
Mediated cell killing
CD8 T cells express Fas ligand –> activate Fas receptor on target cell –> apoptosis of target cell
TNF alpha
Enhance target cell killing
Activate macrophages
Cytokines released by CD8 T cells
IFN gamma, TNF alpha, chemokines
Hyper IgE Syndrome (HIES)
Caused by mutations in STAT3, DCK8, Tyk2
Without STAT 3 –> tries to use TH2 response –> doesn’t work
STAT3
Drives TH17 response
Autosomal dominant HIES
Mutation in STAT3
Facial deformity
Dental problems: don’t lose baby teeth
Autosomal recessive HIES
Mutation in DOCK8 or Tyk2
Severe viral infections and allergic symptoms
No dental or facial issues
Hemophagocytic Lymphohistiocytosis
Mutation in perforin or proteins needed for granule release
Can’t clear viral infections –> continuous inflammation –> cytokine storm disease
Similar to Bare Lymphocyte Disease but can’t even use NK cells to clear infection
Cortical epithelial cells
In cortex of thymus
Produces metabolite factors
Express MHC 1 and 2 –> start of + and - selection
Medullary thymic epithelial cells
Can express almost every protein made in the body
Source of self peptides that are used in self testing of T cells
AIRE
transcriptional chromatin regulator
Removes suppressed gene expression –> allows for promiscuous expression of proteins in medullary thymic epithelial cells
List the immunologically privileged organs
Brain
Eye
Testies
Uterus
CTLA-4
Inhibit CD28 binding to B7 ligands
Expressed by regulatory T cells when it’s time to contract
Binds to B7 w/ higher affinity that CD28
PD-1
Phosphotase (dephosphorylates)
Suppress signaling induced by TCR and costimulatory receptors
Upregulated in TCR and CD28-stimulated T cells
Pd-1 ligands expressed on DC and cell types during inflammation
FOXP3
Expressed in regulatory T cells
Controls differentiation and function of regulatory T cells
Epigenetic regulator
CD25
On regulatory T cells that binds IL-2 to inhibit T cell differentiation