Neural crest derived pericytes promote egress of mature thymocytes at the corticomedullary junction
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Marcus A. Zachariah and  Jason G. Cyster [email protected], 14.02.2011 Bahram Kasmapour PowerPoint PPT Presentation


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Neural Crest–Derived Pericytes Promote Egress of Mature Thymocytes at the Corticomedullary Junction. Marcus A. Zachariah and  Jason G. Cyster [email protected], 14.02.2011 Bahram Kasmapour. Research Article. Background. Lymphocyte circulation:

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Marcus A. Zachariah and  Jason G. Cyster [email protected], 14.02.2011 Bahram Kasmapour

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Neural crest derived pericytes promote egress of mature thymocytes at the corticomedullary junction

Neural Crest–Derived Pericytes Promote Egress of Mature Thymocytes at the Corticomedullary Junction

Marcus A. Zachariah and Jason G. Cyster

[email protected], 14.02.2011

Bahram Kasmapour

Research Article


Background

Background

  • Lymphocyte circulation:

    • constant circulation & survey of secondary lymphoid organs

    • Entering lymphoid organs: selectins, chemokine receptors and integrins

    • Leaving lymphoid organs:

      • Myriocin discovered in screening for imm. Supressor drugs FTY720

      • FTY720 is similar to lipid Sphingosine  phosphorylation  Potent agonist for lysophospholipid S1P receptor(s) : S1P1

      • S1P1: a G-protein coupled receptor

      • “Signaling sphingolipid”

      • Can block egress

Spleen, lymph nodes,

peyer’s patches, …

?


Background1

Background

  • Egress based on S1P concentration difference: blood vs. lymph (6-fold Δ)

  • S1P not produced only by erythrocytes in plasma…

  • Lymph source of S1P lymphatic endothelial cells (LEC)?

    • Mature lymphocytes express S1P1: through Kruppel-like factor (KLP2)

    • Egress route? blood or lymph?

      • Transmigration through corticomedullary junction? Thymic lymphatics?

  • Model of egress:

  • Schwab et al., Nature Immunology, 2007


    S1p1 is sufficient to mediate egress of immature t cells

    S1P1 is sufficient to mediate egress (of immature T-cells)

    A&D: transgenic lines carrying S1P1 transgene

    DP: double positive (CD4+/CD8+)  TH or TC

    SP: single positive (CD4) TH

    high

    high

    High S1P1 expression level

    It responds to S1P as chemotaxis signal


    S1p1 is sufficient to mediate egress of immature t cells1

    S1P1 is sufficient to mediate egress (of immature T-cells)

    ↑ in blood & spleen ↓ in thymus

    DP ↑ presence in spleen


    S1p1 is sufficient to mediate egress of immature t cells2

    S1P1 is sufficient to mediate egress (of immature T-cells)

    • Premature egress?

      • Intercrossed A line with RAG-GFP reporter mice

      • RAG-1+ (GFP+) during maturation, decay over few days time

    • S1P1 only KLF2 target?

      • Bred A line with KLF2f/f-CD4Cre mice (conditional KO)

      • Selective deletion of KLF2 in DP stage

    Mature SP T-cells

    ↑ recent Thymic immigrants (immature)

    present in periphery

    No difference

    (transgene)

    S1P1 is the essential KLF2 target gene needed for egress


    Perivascular accumulation of s1p1 transgenic t cells

    Perivascular accumulation of S1P1 transgenic T cells

    Laminin & CK5+: epithelial & endothelial basement membrane

    ERTR7+/PDGFRβ+: pericytes (special blood vessel ensheathing support cells)

    Bone marrow

    S1P1 dependent perivascular accumulation, disrupted by FTY720

     More S1P and/or higher sensitivity of A line


    Intravascular labeling reveals emigrating thymocytes

    Intravascular labeling reveals emigrating thymocytes

    • Intravenous injection with α-CD4-PE  thymus isolated shortly thereafter

    Small but reproducible thymic DP population detected (not from blood)

    CD-PE+ in blood vessels of cortex and medulla


    Intravascular labeling reveals emigrating thymocytes1

    Intravascular labeling reveals emigrating thymocytes

    FTY720 blocks egress (?)

    DC69

    Recent migration, not blood circulating thymocytes

    CD69 regulates timing of egress (could help with full selection and maturation)


    Thymocytes emigrate by blood vessels at the corticomedullary junction cmj

    Thymocytes emigrate by blood vessels at the corticomedullary junction (CMJ)

    In vivo labled CD4 SP in thymus, CD31 for vascular endothelium

    CD8 for cortical regions

    Thymocyte with

    in 50µm of CMJ

    ~70 thymocytes per section and 2500 per thymus  estimated 1% of total or 1E6 per day egress to blood

    Thymocyte imaged during egress to blood


    Neural crest derived pericytes promote thymocyte egress

    N.crest ΔSphk

    mice ΔSphk

    Neural crest-derived pericytes promote thymocyte egress

    Pericytes: diverse population of cells closely ensheating blood vessels

    Thymic prevascular cells  neural crest origin*  encountered before endothelium

    T-cell acumulation... Pericytes producing S1P?

    S1P has (also) a pericyte origin

    S1P1 up-regulation

    Less DC4+ in blood (?)

    Less recent migrants in PLN


    Neural crest derived pericytes promote thymocyte egress1

    Neural crest-derived pericytes promote thymocyte egress

    Accumulation of mature SP Thymocytes

    S1P needed for CD69 down-regulation during maturation

    Normal pericyte distribution


    Lymphatic s1p is not required for thymic egress

    Lymphatic S1P is not required for thymic egress

    Abalation (Cre-Rosa26eYFP) of Sph kinsae activity in lymphatic endothelium does not inhibit thymic egress

    GP38+CD31+ : lymphatic endothelial cells (LEC)

    GP38-CD31+: blood vessel endothelial cells (BEC)

    PDGFRβ+CD31-: pericytes

    Thy LEC ΔSphk

    digested thymus

    No increase in mature SP thymocytes in thymus, no major role for lymphatic v.

    Not much LEC in thymus. In LN all LEC are ΔSphk


    Take home messages

    Take home messages…

    • Egress of thymocytes is Sphingosine-1-P dependent

    • S1P receptor, S1P1 is expressed on cell surface

    • S1P1 is only target for KLF2 needed for mature SP egress

    • FTY720 a potent agonist for Lysophospid receptors is derived from Myriocin (fungal )

    • S1P for egress is provided by the cooperation of pericytes/b.v. endothelial and plasma

    • Egress takes place at corticomedullary junction b. vessels

    • No major role for Lymphatic vessles in egress

    • Blocking egress could be used for “safer” immunosuppression for organ transplantation

    Thank you for listening!


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