Download and NK T cells

I.  T Cells
II. Invariant TCR T Cells
 T Cells in Autoimmune and
Infectious Disease
 T cells can account for 30% of the T cell
infiltrate in MS lesions (Wucherpfennig, K. W.,
et. al. PNAS 89:4588).
 T cells expand from 5 to 17% of PBMCs in
patients during acute stages of P. Falciparum
(Ho, M. et. al. Infect Immun. 62: 855–862).
Similar  T cell expansion has been observed in
M. Tuberculosis infection and Chron’s disease.
 KO Mice Reveal a Unique role
for Gamma Delta T Cells
Infections agents can be lethal
Gram-positive Nocardia asteroides Causes
Lethal Infection in  T Cell KO Mice
Tam et. al., Infection & Immunity, 2001 69:6165.
Lung Sections of Mice Infected with
Aerosolized Gram-positive N. asteroides
B6
-/- KO
 Neutrophils in -/- mice
N. asteroides (dark
blue stain)
Tam et. al., Infection & Immunity, 2001 69:6165.
 KO mice reveal a unique role for
Gamma Delta T cells
Certain infections can be lethal.
Most infections reveal inflammatory defects in 
KO mice.
Pathological outcome is different than that of 
KO mice—which usually die upon infectious
challenge.
Skin wound healing is impaired.
 T Cells Distribute Differently Then  T Cells
Anatomically located lining the epithelial tissues
Small numbers (1-2% of cells) found in the lymphoid
tissues, spleen and lymph nodes
 might play a role early in the immune response
Skin (V5 V1)
Reproductive Tract
Respiratory Tract
Small Intestine (IELs)
What do Gamma Delta TCRs
recognize?
CDR3 Length Distribution of Immune Receptor Chains
B cell receptor
Ag
 T cell receptor
MHC
 T cell receptor
Ag
?
Ed Rock, et. al.
What do Gamma Delta TCRs
recognize?
MHC class II, IEk.
LBK5*  T cell clone recognizes backbone residues of
class II IEk and recognition is independent of the
presented peptide.
Important residues for
LBK5 stimulation
*LBK5 was generated from immunization with non-MHC
matched splenocytes.
Significance of IEk Recognition?
Unlike MHC restricted  T cell clones, peptide
does not confer reactivity of LBK5 to IEk.
Gamma delta T cells recognize antigens in a
fundamentally different way than  T cells.
Gamma delta development seems to be normal
in b2m-/- and MHC II negative mice, which
suggest that the many of the  TCR ligands are
not conventional MHC molecules.
What do Gamma Delta TCRs
Recognize?
MHC class II, IEk
HSV-gI envelope protein
HSV-1
gI envelope protein is
left on the cell surface
Viral DNA
TgI4*  T Cell Clone is Stimulated
by Plate Bound HSV-gI Protein
Cell lysis blocked by -TCR and -gI mAbs.
*TgI4 was recovered from mice inoculated (I.V.) with HSV-1.
Sciammas, R. et. al. J. Exp. Med 185:1969
Significance of HSV-gI Interaction?
Like B cell Ig receptors,  TCRs can
recognize protein directly without need for
processing and presentation upon MHC
molecules.
HSV-1
TgI4
Cytolitic
activity
 T Cell
TCR
gI envelope protein is
left on the cell surface
Viral cDNA
What do Gamma Delta TCRs
Recognize?
MHC class II, IEk
gI HSV envelope protein
Non-classical MHC T22/T10
T22 Tetramer Binds High Frequencies
of  T Cells
T22 tetramer
Non-immunized mice
•T22 can’t present antigens because
of its ‘truncated’ MHC  barrel.
 TCR
Crowley, M. et. al. Science 2000, 287:314
•T22 is upregulated on APCs upon
CFA immunization or LPS stimulation.
•Affinity measurements can be made
between G8  TCR and T22.
Significance of T22 Recognition?
Self or ‘natural’ ligand
This ligand is not recognized by  TCRs,
suggesting that the  TCR recognize nonoverlapping ‘cues’ through the  TCR.
Significance of T22 Recognition?
T cell Status of immune system
Frequency1
T10/T22- specific  T cells
~ 1/250
MHC/peptide specific  T cells
(not primed)
~ 1/1,000,000
MHC/peptide specific  T cells
(Immunized; effector phase)
~1/2-1/100
High frequencies = fast immune responses to ligand
What do Gamma Delta TCRs
recognize?
MHC class II, IEk
gI HSV envelope protein
Non-classical MHC T22/T10
Small phosphate antigens
Small Alkyl-Phosphate Antigens are Secreted by Bacteria
and Also Expressed in Mammalian Tissues.
Small phosphate antigens stimulate
human and monkey V2 V2 T cells
(Shen, Science, 295:2255-8).
V2 V2 T cells expand (15-60%) in
response to a variety of infectious
agents.
Reactivity is mediated through the 
TCR and the CDR3 is important for
reactivity (Bukowski, J. I. 161:286)
Cell contact is required (Morita,
Immunity 3:495).
No processing is required (fixed cells +
small phosphate antigen = stimulation)
(Morita, Immunity 3:495).
Significance of Small Phosphate
 TCR Recognition?
Ligands can either be self or foreign.
Small phosphates are produced by the
nucleotide salvage pathway, during
cellular stress (i.e. heat shock, starvation,
etc.) (Constant, P. Science 264:267).
Suggesting that  T cells monitor cellular
stress.
Other Reports of  TCR Ligands
MICA – a non classical MHC that is upregulated
on tumor cells and upon heat shock (Wu, J. et.
al. J. I. 169:1236).
CD1c- No addition of antigen is required (Spada
F et. al. JEM March 2000).
Hsp60 has been reported to be stimulatory.
Qa-1b can stimulate  T cells.
 T Cell Summary
 T cells can recognize self (MHC and MHClike) and foreign ligands (HSV-gI, small
phosphate antigens).
Many of the ligands are up regulated on the
surface of cells upon infection or stress.
Taken together  T cells might ‘see’ cell surface
perturbations in homeostasis through their TCR
and regulate the immune response.
 T Cell
T22
Small
phosphate
antigens
LPS
Cell
‘Non-homeostatic’ Cell
Viral derived surface Antigens
II. Invariant TCR T cells.
Invariant TCR T cells clonally/oligoclonally
express TCRs with a limited
P/N/Junctional CDR3 diversity.
High frequencies are found in specific
tissues.
NK T cells, DETC  T cells, MAIT cells.
Invariant NK T cells (iNK T cells)
Defined as being reactive to CD1d.
Express the invariant V and limited V TCRs.
iNK T cells represent the majority of T cells
found in the liver.
1-3% found in the spleen.
Express markers found on NK cells.
V TCR sequences of CD1d restricted iNK T cells
Mouse V14
P/N
TGT GTG GTG GGC GCA C
1 TGT GTG GTG GGC
CVVG
2 TGT GTG GTG GG
DRGSA
G
CVVG
GTA GAT AGA GGT TCA GCC
CVV
CVVG
Human V24
CVVS
GAT AGA GGT TCA GCC
DRGSA
3 TGT GTG GTG
4 TGT GTG GTG GG
J281
C TGT GTA GAT AGA GGT TCA GCC
GAT AGA GGT TCA GCC
VDRGSA
T GAC
D
P/N
AGA GGT TCA GCC
RGSA
JQ
DRGST
Lantz, O. and Bendelac, A., J. Exp. Med. 180:1097, 1994.
What do the iNK T cells recognize?
CD1d plus….
An unidentified endogenous self-glycolipid antigen.
•-GlcCer synthase KO APCs fail to
stimulate galcer/CD1d1 restricted NK T
cells (Stanic et al. PNAS, 2003).
•Selected by CD1, CD8, CD4, positive
cells in the thymus (Nat Immunol. 2:971).
-Galactosylceramide and iNK T cells
-carbon linkage
• CD1 family of B2m dependent class Ib proteins that can present a
variety of lipid antigens to CD1 restricted T cells.
• 80% of NK T cells (NK1.1+) in both mouse and human express an
invariant TCR (mV14-J281, hV24-JQ) that recognize CD1d
loaded with -GalCer.
• Mammalians do not synthesize -GalCer which is derived from sea
sponges.
-Galcer is likely a structural mimic of a
‘self’ or ‘natural’ ligand.
iNK T cells are specific for CD1d1 -Galcer
Loaded with a-Galcer
1000
0.029
Not preloaded
1.35
0
2.09e-3
100
PhyEry
PhyEry
CD1d tetramer
100
1000
10
1
10
1
13.8
0.1
0.1
84.8
1
10
Fluor
100
TCR 
1000
12.6
0.1
0.1
87.4
1
10
Fluor
100
1000
iNK T cell function
Rapidly (within 1-2 hours) secrete IFN-
and/or IL-4 upon stimulation in vivo
(Yoshimoto T J. Exp. Med. 179:1285).
J281-/- mice lack iNK T cells and have
delayed immune responses to a variety of
infectious agents.
Dendritic Epidermal  T cells
(DETCs) promote wound healing
-/B6
Jameson et. al. Science 296:747
What is the DETC TCR ligand?
We don’t know….
Heat shocked keratinocytes stimulate
DETC cells in a TCR dependent fashion
(Haravan, W. Science 252:1430).
This ligand is not sensitive to trypsin
treatment (unpublished results), therefore
is most likely not a protein.
Table summarizing invariant T cell phenotypes
Cell
NK T
MAIT
DETC
Conserved
in Mouse
and Man?
iTCR
(mouse)
Development is
dependent upon:
Yes
Va14Ja281
CD4+,CD8+, CD1+
Thymocytes
Yes
Va19Ja33
B cells, MR1+,
Microbial Flora
Vg5 Vd1
Conformationally
dependent fetal
TCR expression
No
Ligand
Location
Autoreactive
Negatively
selected?
? (similar to aGalcer)
Liver, Spleen
Yes
?(No in
most
models)
?
Gut Lamina
Propria
Yes
?
Yes
? (Yes, in
some
models)
? (not a
protein)
Skin
First line of Defense
Invariant and gamma delta T cells respond
quickly to antigenic stimulus.
Should these T cells be classified as being
apart of the innate immune system or not?