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					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


                                                       Ag
 B cell receptor




 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


                                            T Cell         Cytolitic
                                                             activity


                                                       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
                Non-immunized mice
T22 tetramer




                                            •T22 can’t present antigens because
                                            of its ‘truncated’ MHC  barrel.
                                            •T22 is upregulated on APCs upon
                                            CFA immunization or LPS stimulation.
                          TCR
                                            •Affinity measurements can be made
Crowley, M. et. al. Science 2000, 287:314   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 non-
overlapping ‘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 MHC-
like) 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                         J281
             TGT GTG GTG GGC GCA C           C TGT GTA GAT AGA GGT TCA GCC
           1 TGT GTG GTG GGC                           GAT AGA GGT TCA GCC

             CVVG                                              DRGSA
           2 TGT GTG GTG GG           G               GAT AGA GGT TCA GCC

             CVVG                                              DRGSA
           3 TGT GTG GTG                          GTA GAT AGA GGT TCA GCC

             CVV                                             VDRGSA
           4 TGT GTG GTG GG          T GAC                AGA GGT TCA GCC

             CVVG                     D                          RGSA
   Human V24                        P/N                            JQ

             CVVS                                              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                                   Not preloaded
                1000                                                   1000
                                 0.029                         1.35                     0                            2.09e-3



                    100                                                    100
CD1d tetramer
                PhyEry




                                                                       PhyEry
                         10                                                     10




                           1                                                      1



                                 13.8                          84.8                     12.6                           87.4
                         0.1                                                    0.1
                               0.1        1      10     100     1000                  0.1        1      10     100       1000
                                                Fluor                                                  Fluor


                                                 TCR 
        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


         Conserved
         in Mouse    iTCR      Development is                                        Auto-      Negatively
Cell     and Man?    (mouse)   dependent upon:    Ligand             Location        reactive   selected?
                                                                                                ?(No in
                     Va14-     CD4+,CD8+, CD1+    ? (similar to a-                              most
NK T     Yes         Ja281     Thymocytes         Galcer)            Liver, Spleen   Yes        models)

                     Va19-     B cells, MR1+,                        Gut Lamina
MAIT     Yes         Ja33      Microbial Flora    ?                  Propria         Yes        ?
                               Conformationally                                                 ? (Yes, in
                               dependent fetal    ? (not a                                      some
DETC     No          Vg5 Vd1   TCR expression     protein)           Skin            Yes        models)
      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?

				
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