T cell development i the generation of tcr thymocytes
This presentation is the property of its rightful owner.
Sponsored Links
1 / 51

T Cell Development I: The Generation of TCR + Thymocytes PowerPoint PPT Presentation


  • 61 Views
  • Uploaded on
  • Presentation posted in: General

T Cell Development I: The Generation of TCR + Thymocytes. Questions for the next 2 lectures: How do you generate a diverse T cell population with functional TCR rearrangements? How do you generate a T cell population that is self-MHC restricted?

Download Presentation

T Cell Development I: The Generation of TCR + Thymocytes

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


T cell development i the generation of tcr thymocytes

T Cell Development I: The Generation of TCR+ Thymocytes


T cell development i the generation of tcr thymocytes

Questions for the next 2 lectures:

How do you generate a diverse T cell population with functional TCR rearrangements?

How do you generate a T cell population that is self-MHC restricted?

How do you ensure that those diverse T cell receptors are not-self reactive?

How do you coordinate lineage specification with MHC specificity and coreceptor expression?

•  vs.  T cell

• CD4 vs. CD8


T cell development i the generation of tcr thymocytes

The pathway of T cell development

T cells...precursors are born in the bone marrow and “educated” in the thymus.

  • The thymus “involutes” with age

  • DiGeorge Syndrome, Nude mice


T cell development i the generation of tcr thymocytes

Nude Mice

A. Human (mammal) skin after 60 days.

B. Cat (mammal) skin at 51 days.

C. Chicken (bird) at 32 days;

D. Chameleon (reptile) at 41 days.

E. Fence lizard (reptile)at 28 days.

F. Tree frog (amphibian) at 40 days.


T cell development i the generation of tcr thymocytes

The Thymus is required for T cell development

scid mutation:

DNA PK

no gene rearrangement

nude mutation:

transcription factor required for

terminal epithelial differentiation

(whn)

NO THYMUS

NO B or T CELLS


T cell development occurs in the thymus

T cell development occurs in the thymus


T cell development i the generation of tcr thymocytes

Figure 5-3 part 1 of 2


The epithelial cells developing thymocytes

The epithelial cells & developing thymocytes


T cell development can be characterized using flow cytometry

T cell development can be characterized using flow cytometry


Real data

Double-positives

CD4 single-positive

88

8

CD4

Double-negatives

CD8 single-positive

1

3

CD8

Real data


Dn s can be further subdivided into dn1 through dn4

DN’s can be further subdivided into DN1 through DN4

CD25 (a chain of IL2R)

“Gate” on CD4-CD8-, analyze for CD44 and CD25


The real data

CD25

The real data

(gated on DN cells)


Double negative cells appear in the fetal thymus before double positive cells

Double negative cells appear in the fetal thymus before double positive cells

K. Hogquist


T cell populations during development and in the lymphoid tissue

T cell populations during development and in the lymphoid tissue

THYMUS

SPLEEN

CD4

CD8


T cell development i the generation of tcr thymocytes

Thymocytes at different developmental stages are found in distinct parts of the thymus

Maturation


T cell development i the generation of tcr thymocytes

Today

Thursday


T cell development i the generation of tcr thymocytes

Most cells fail to complete thymocyte maturation


T cell development i the generation of tcr thymocytes

Most developing thymocytes die in the thymus

apoptotic cells

(DNA fragmentation)

macrophages

Macrophages...garbage collectors, contain the dying cells


T cell development i the generation of tcr thymocytes

T cell development involves the sequential generation, assembly and testing of the newly rearranged TCR


T cell development i the generation of tcr thymocytes

TCR rearrangement is very similar to Ig rearrangement


Figure 5 6 part 1 of 3

First step: TCRbeta rearrangement

Figure 5-6 part 1 of 3


Figure 5 6 part 2 of 3

Figure 5-6 part 2 of 3


T cell development i the generation of tcr thymocytes

How do you test for successful TCRbeta chain rearrangements if you have not rearranged TCRalpha?

Pre-Talpha

Pre-T cell receptor


Tcr chain is required for dn to dp transition experimental evidence

TCR  chain is required for DN to DP transition:Experimental Evidence

TCRa-/-

TCRb-/-

TCRa/b-/-

TCRb/d-/-

WT

108

108

<107

<107

106

Total

thymocyte

numbers

Expressing

TCRgd

CD4

CD8


T cell development i the generation of tcr thymocytes

Does the pre-TCR have a ligand?

Remove extracellular domains…

…and examine T cell development

(work of Nigel Killeen, UCSF)


T cell development i the generation of tcr thymocytes

Pre-TCR extracellular domains are not required!

pTaT;bTreceptor restores CD4+8+ development and thymocyte expansion

(Irving (1998) Science 280:905)


T cell development i the generation of tcr thymocytes

CD25

b-selection leads to proliferation

DN2

Gated on CD4/CD8 DNs

DN3

Proliferating cells are bigger

Forward scatter

(cell size)


T cell development i the generation of tcr thymocytes

TCR b locus has two D-J clusters

Allows a 2nd rearrangement if 1st is nonproductive


T cell development i the generation of tcr thymocytes

We are here


T cell development i the generation of tcr thymocytes

Progression through development

correlates with rearrangement


T cell development i the generation of tcr thymocytes

At the DP stage, TCRalpha rearrangement begins


T cell development i the generation of tcr thymocytes

TCR a locus has 50 Ja segments


T cell development i the generation of tcr thymocytes

TCRa locus-- replacement rearrangement


Dp thymocytes express surface tcr

DP thymocytes express surface TCR

CD3 lo cell-- pre-TCR

CD3 hi cells-- TCR


Tcr chain is required for dp to sp transition experimental evidence

TCR  chain is required for DP to SP transition:Experimental Evidence

TCRa-/-

TCRb-/-

TCRa/b-/-

TCRb/d-/-

WT

108

108

<107

<107

106

Total

thymocyte

numbers

Expressing

TCRgd

CD4

CD8


T cell development i the generation of tcr thymocytes

Differential expression of Src family kinases


Remember what lck does

Remember what Lck does


T cell development i the generation of tcr thymocytes

Role of Lck in T cell development

RAG KO

TCRTransgene

RAG KO x Lck KO

TCRTransgene

RAG KO

CD4

CD8

Total

thymocyte

number

0.4 x 106

288 x 106

10 x 106

30-fold reduction in DPs!


T cell development i the generation of tcr thymocytes

 vs 

Thursday


T cell development i the generation of tcr thymocytes

A model for  versus  lineage commitment


T cell development i the generation of tcr thymocytes

TCR rearrangement removes the delta locus


T cell development i the generation of tcr thymocytes

TCR lineage comprises the majority of T cells

90%

10%


T cell development i the generation of tcr thymocytes

gdT cells are favored

during early fetal development


T cell development i the generation of tcr thymocytes

Waves of  T cells with specific TCR usage

develop early gestation


T cell development i the generation of tcr thymocytes

Waves of  T cells home to different tissues


T cell development i the generation of tcr thymocytes

gd cells bearing specific receptors end up in skin (Vg5), gut (Vg2), uterus (Vg6), etc.

Limited junctional diversity: no N nucleotides (no TdT)

The mechanisms controlling this limited rearrangement are poorly understood.

Early waves of  T cells


T cell development i the generation of tcr thymocytes

Antigen recognition by  T cells is different than  T cells

 T cells are not MHC restricted!

Antigen is recognized directly, more like an antibody

In some cases ligands for the  TCR are self proteins upregulated under stress conditions

In humans, circulating  cells recognize a phospholipid antigen from Mycobacterium tuberculosis


T cell development i the generation of tcr thymocytes

Dendritic epidermal T cells (DETC)

Vg5 gd T cells home to the skin and wedge among keratinocytes

Involved in wound healing as well as tumor protection


Detcs promote wound healing

DETCs promote wound healing


T cell development i the generation of tcr thymocytes

Roles of gd T cells in cancer

• gd-knockout mice have a higher incidence of skin cancers induced by carcinogens, including DMBA/TPA (tumor initiator/promoter) (shown in figure) or methylcolanthrene (MCA).

• The protection is mediated by DETC resident in the mouse skin

Appearance of tumor cells in knockout versus wildtype mice treated with carcinogen

Girardi et al, Science 294:605 (2001)


  • Login