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Downregulation of CD1 marks acquisition of functional maturation of human thymocytes and defines a control point in late stages of human T cell development.

Res P, Blom B, Hori T, Weijer K, Spits H - J. Exp. Med. (1997)

Bottom Line: Using the capacity of thymocytes to expand in vitro in response to PHA and IL-2 as a criterion for functional maturity, we found that functional maturity of both SP and DP thymocytes correlates with downregulation of CD1a.CD1a+CD4+ SP thymocytes do not represent an end stage population because purified CD1a+CD4+ SP thymocytes differentiate to expandable CD1a- cells upon cocultivation with human thymic stromal cells.Taken together these data indicate that when CD1a+ DP TCR alpha beta low cells mature, these cells interact with MHC, but that an additional, apparently species-specific, signal is required for downregulation of CD1a to generate functional mature TCR alpha beta + cells.

View Article: PubMed Central - PubMed

Affiliation: Netherlands Cancer Institute, Amsterdam, Netherlands.

ABSTRACT
We have investigated whether in the human thymus transition of CD4+CD8+ double positive (DP) to CD4+ or CD8+ single positive (SP) cells is sufficient for generation of functional immunocompetent T cells. Using the capacity of thymocytes to expand in vitro in response to PHA and IL-2 as a criterion for functional maturity, we found that functional maturity of both SP and DP thymocytes correlates with downregulation of CD1a. CD1a- cells with a persistent DP phenotype were also found in neonatal cord blood, suggesting that at least a proportion of mature DP cells can emigrate from the thymus. The requirements for generating functional T cells were investigated in a hybrid human/mouse fetal thymic organ culture. MHC class II-positive, but not MHC class II-negative, mouse thymic microenvironments support differentiation of human progenitors into TCR alpha beta+CD4+ SP cells, indicating that mouse MHC class II can positively select TCR alpha beta +CD4+ SP human cells. Strikingly, these SP are arrested in the CD1a+ stage and could not be expanded in vitro with PHA and IL-2. CD1a+CD4+ SP thymocytes do not represent an end stage population because purified CD1a+CD4+ SP thymocytes differentiate to expandable CD1a- cells upon cocultivation with human thymic stromal cells. Taken together these data indicate that when CD1a+ DP TCR alpha beta low cells mature, these cells interact with MHC, but that an additional, apparently species-specific, signal is required for downregulation of CD1a to generate functional mature TCR alpha beta + cells.

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CD1a expression on CD3+TCR αβ+ and CD3+TCR αβ−  (TCR γδ+) cells, harvested from an FTOC incubated for 4 wk with  CD34+CD1a− postnatal thymocytes. FTOC-derived cells were stained  with CD1a FITC, TCR αβ PE, and CD3 TRC. The dot plot demonstrates the pattern of TCR αβ PE versus CD3 TRC staining. The histograms indicate CD1a FITC expression of the CD3high cells that express  TCR αβ, and the CD3int and CD3high TCR αβ− cells which represent  the immature and mature γδ T cells, respectively.
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Figure 4: CD1a expression on CD3+TCR αβ+ and CD3+TCR αβ− (TCR γδ+) cells, harvested from an FTOC incubated for 4 wk with CD34+CD1a− postnatal thymocytes. FTOC-derived cells were stained with CD1a FITC, TCR αβ PE, and CD3 TRC. The dot plot demonstrates the pattern of TCR αβ PE versus CD3 TRC staining. The histograms indicate CD1a FITC expression of the CD3high cells that express TCR αβ, and the CD3int and CD3high TCR αβ− cells which represent the immature and mature γδ T cells, respectively.

Mentions: Having established that MHC class II antigens can support development of human CD4+ SP T cells, we next investigated whether the mouse thymic environment can induce downregulation of CD1a and functional maturation. Early thymic CD34+CD1a− progenitors were isolated and cultured in FTOC for 4 wk. Analysis of the cells harvested from the FTOC revealed the presence of TCR αβ and TCR γδhigh cells. Almost all TCR αβhigh cells expressed CD1a, while most TCR γδhigh cells lacked CD1a (Fig. 4). Immature TCR γδdim cells mostly expressed CD1a (Fig. 4). Stimulation of the cells harvested from the FTOC with a feeder cell mixture, PHA, and IL-2 resulted in expansion mostly of TCR γδ+ cells and few TCR αβ+ cells (Fig. 5). Most of those TCR αβ+ cells that were expanded expressed CD4 (Fig. 5). These data demonstrate that although the mouse MHC class II–positive mouse thymic environment can support development of CD4+ SP thymocytes, it is very inefficient in induction of functional maturation of these cells. By contrast, the mouse thymic microenvironment efficiently induces maturation of TCR γδ+ cells. Thus, failure of the mouse MHC class II–positive environment to induce functional maturation of TCR αβ+ cells is not due to a intrinsic incapability to support maturation of human T cells.


Downregulation of CD1 marks acquisition of functional maturation of human thymocytes and defines a control point in late stages of human T cell development.

Res P, Blom B, Hori T, Weijer K, Spits H - J. Exp. Med. (1997)

CD1a expression on CD3+TCR αβ+ and CD3+TCR αβ−  (TCR γδ+) cells, harvested from an FTOC incubated for 4 wk with  CD34+CD1a− postnatal thymocytes. FTOC-derived cells were stained  with CD1a FITC, TCR αβ PE, and CD3 TRC. The dot plot demonstrates the pattern of TCR αβ PE versus CD3 TRC staining. The histograms indicate CD1a FITC expression of the CD3high cells that express  TCR αβ, and the CD3int and CD3high TCR αβ− cells which represent  the immature and mature γδ T cells, respectively.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2196108&req=5

Figure 4: CD1a expression on CD3+TCR αβ+ and CD3+TCR αβ− (TCR γδ+) cells, harvested from an FTOC incubated for 4 wk with CD34+CD1a− postnatal thymocytes. FTOC-derived cells were stained with CD1a FITC, TCR αβ PE, and CD3 TRC. The dot plot demonstrates the pattern of TCR αβ PE versus CD3 TRC staining. The histograms indicate CD1a FITC expression of the CD3high cells that express TCR αβ, and the CD3int and CD3high TCR αβ− cells which represent the immature and mature γδ T cells, respectively.
Mentions: Having established that MHC class II antigens can support development of human CD4+ SP T cells, we next investigated whether the mouse thymic environment can induce downregulation of CD1a and functional maturation. Early thymic CD34+CD1a− progenitors were isolated and cultured in FTOC for 4 wk. Analysis of the cells harvested from the FTOC revealed the presence of TCR αβ and TCR γδhigh cells. Almost all TCR αβhigh cells expressed CD1a, while most TCR γδhigh cells lacked CD1a (Fig. 4). Immature TCR γδdim cells mostly expressed CD1a (Fig. 4). Stimulation of the cells harvested from the FTOC with a feeder cell mixture, PHA, and IL-2 resulted in expansion mostly of TCR γδ+ cells and few TCR αβ+ cells (Fig. 5). Most of those TCR αβ+ cells that were expanded expressed CD4 (Fig. 5). These data demonstrate that although the mouse MHC class II–positive mouse thymic environment can support development of CD4+ SP thymocytes, it is very inefficient in induction of functional maturation of these cells. By contrast, the mouse thymic microenvironment efficiently induces maturation of TCR γδ+ cells. Thus, failure of the mouse MHC class II–positive environment to induce functional maturation of TCR αβ+ cells is not due to a intrinsic incapability to support maturation of human T cells.

Bottom Line: Using the capacity of thymocytes to expand in vitro in response to PHA and IL-2 as a criterion for functional maturity, we found that functional maturity of both SP and DP thymocytes correlates with downregulation of CD1a.CD1a+CD4+ SP thymocytes do not represent an end stage population because purified CD1a+CD4+ SP thymocytes differentiate to expandable CD1a- cells upon cocultivation with human thymic stromal cells.Taken together these data indicate that when CD1a+ DP TCR alpha beta low cells mature, these cells interact with MHC, but that an additional, apparently species-specific, signal is required for downregulation of CD1a to generate functional mature TCR alpha beta + cells.

View Article: PubMed Central - PubMed

Affiliation: Netherlands Cancer Institute, Amsterdam, Netherlands.

ABSTRACT
We have investigated whether in the human thymus transition of CD4+CD8+ double positive (DP) to CD4+ or CD8+ single positive (SP) cells is sufficient for generation of functional immunocompetent T cells. Using the capacity of thymocytes to expand in vitro in response to PHA and IL-2 as a criterion for functional maturity, we found that functional maturity of both SP and DP thymocytes correlates with downregulation of CD1a. CD1a- cells with a persistent DP phenotype were also found in neonatal cord blood, suggesting that at least a proportion of mature DP cells can emigrate from the thymus. The requirements for generating functional T cells were investigated in a hybrid human/mouse fetal thymic organ culture. MHC class II-positive, but not MHC class II-negative, mouse thymic microenvironments support differentiation of human progenitors into TCR alpha beta+CD4+ SP cells, indicating that mouse MHC class II can positively select TCR alpha beta +CD4+ SP human cells. Strikingly, these SP are arrested in the CD1a+ stage and could not be expanded in vitro with PHA and IL-2. CD1a+CD4+ SP thymocytes do not represent an end stage population because purified CD1a+CD4+ SP thymocytes differentiate to expandable CD1a- cells upon cocultivation with human thymic stromal cells. Taken together these data indicate that when CD1a+ DP TCR alpha beta low cells mature, these cells interact with MHC, but that an additional, apparently species-specific, signal is required for downregulation of CD1a to generate functional mature TCR alpha beta + cells.

Show MeSH
Related in: MedlinePlus