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Negative selection in the thymus includes semimature T cells.

Kishimoto H, Sprent J - J. Exp. Med. (1997)

Bottom Line: However, being relatively mature, medullary T cells are thought to be beyond the stage of tolerance induction.These findings suggest that the differentiated T cells reaching the medulla from the cortex remain sensitive to tolerance induction for a brief period before acquiring a fully mature tolerance-resistant phenotype.The semimature subset of medullarsy T cells displays unique requirements for tolerance induction; depending upon the conditions used, tolerizing these cells can involve either a Fas (CD95)-dependent or a Fas-independent pathway.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, IMM4, The Scripps Research Institute, La Jolla, California 92037, USA.

ABSTRACT
The thymic medulla plays a key role in negative selection (self-tolerance induction) and contains differentiated T cells en route to the extrathymic environment. However, being relatively mature, medullary T cells are thought to be beyond the stage of tolerance induction. This paradox is resolved by the finding that medullary T cells (CD4+8- thymocytes) comprise two distinct subsets. Medullary thymocytes expressing a fully mature (HSAlo) phenotype are strongly resistant to tolerance induction, whereas cells with a semimature (HSAhi) phenotype are tolerance susceptible. These findings suggest that the differentiated T cells reaching the medulla from the cortex remain sensitive to tolerance induction for a brief period before acquiring a fully mature tolerance-resistant phenotype. The semimature subset of medullarsy T cells displays unique requirements for tolerance induction; depending upon the conditions used, tolerizing these cells can involve either a Fas (CD95)-dependent or a Fas-independent pathway.

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Apoptosis of thymocyte subsets and LN T cells  induced by stimulation with  anti-TCR mAb or anti-TCR  plus anti-CD28 mAbs in vitro.  Purified populations of CD4+8+,  HSAhi CD4+8−, and HSAlo  CD4+8− thymocytes and  CD4+8− LN cells were cultured  for 20 h in vitro on plates coated  with anti-TCR mAb alone  (H57, 10 μg/ml) or with a mixture of anti-TCR (10 μg/ml)  and anti-CD28 (20 μg/ml)  mAbs. (A) The purity of the subsets before culture (left) and the  extent of apoptosis determined  by TUNEL staining after culture  (right) are shown; for TUNEL  staining, the forward scatter  (FSC) profile shows the relative  size of the cells. (B) Shows surface expression of CD69 and  CD25 (IL-2R) on viable  (TUNEL−) cells after culture. To  exclude the possibility that CD4  ligation during the panning procedure affected the results (50),  parallel experiments were performed with cells that were purified by methods that did not involve CD4 ligation, e.g., by  using unmanipulated thymocytes from β2m−/− mice as a  source of purified CD4+8+ cells  and CD8− IL-2R− normal thymocytes as an enriched source of  CD4+8− cells. The results obtained with these cells were essentially identical to the data  shown in Figs. 3 and 4.
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Figure 2: Apoptosis of thymocyte subsets and LN T cells induced by stimulation with anti-TCR mAb or anti-TCR plus anti-CD28 mAbs in vitro. Purified populations of CD4+8+, HSAhi CD4+8−, and HSAlo CD4+8− thymocytes and CD4+8− LN cells were cultured for 20 h in vitro on plates coated with anti-TCR mAb alone (H57, 10 μg/ml) or with a mixture of anti-TCR (10 μg/ml) and anti-CD28 (20 μg/ml) mAbs. (A) The purity of the subsets before culture (left) and the extent of apoptosis determined by TUNEL staining after culture (right) are shown; for TUNEL staining, the forward scatter (FSC) profile shows the relative size of the cells. (B) Shows surface expression of CD69 and CD25 (IL-2R) on viable (TUNEL−) cells after culture. To exclude the possibility that CD4 ligation during the panning procedure affected the results (50), parallel experiments were performed with cells that were purified by methods that did not involve CD4 ligation, e.g., by using unmanipulated thymocytes from β2m−/− mice as a source of purified CD4+8+ cells and CD8− IL-2R− normal thymocytes as an enriched source of CD4+8− cells. The results obtained with these cells were essentially identical to the data shown in Figs. 3 and 4.

Mentions: To extend these findings, purified subsets of thymocytes were tested for their sensitivity to negative selection (apoptosis) mediated by cross-linked anti-TCR plus anti-CD28 mAbs in vitro; exposure to cross-linked anti-TCR mAb alone was used as a control. Apoptosis was measured by TUNEL staining after overnight culture. Fig. 2 shows the purity of the cells tested (A, left), TUNEL staining of the cultured cells (A, right), and the expression of two activation markers, CD69 and CD25 (IL-2R), on viable (TUNEL−) cells (B); cells were cultured on plates coated with anti-CD28 (20 μg/ml) and/or anti-TCR (10 μg/ml) mAbs. Fig. 3 A shows the effects of culturing the cells with decreasing concentrations of anti-TCR mAb ± a fixed concentration of anti-CD28 mAb (20 μg/ml); background levels of apoptosis found with cells cultured in medium alone have been subtracted, and the data are shown as change in apoptosis. The data in Figs. 2 and 3 A make three points (see Fig. 2, legend).


Negative selection in the thymus includes semimature T cells.

Kishimoto H, Sprent J - J. Exp. Med. (1997)

Apoptosis of thymocyte subsets and LN T cells  induced by stimulation with  anti-TCR mAb or anti-TCR  plus anti-CD28 mAbs in vitro.  Purified populations of CD4+8+,  HSAhi CD4+8−, and HSAlo  CD4+8− thymocytes and  CD4+8− LN cells were cultured  for 20 h in vitro on plates coated  with anti-TCR mAb alone  (H57, 10 μg/ml) or with a mixture of anti-TCR (10 μg/ml)  and anti-CD28 (20 μg/ml)  mAbs. (A) The purity of the subsets before culture (left) and the  extent of apoptosis determined  by TUNEL staining after culture  (right) are shown; for TUNEL  staining, the forward scatter  (FSC) profile shows the relative  size of the cells. (B) Shows surface expression of CD69 and  CD25 (IL-2R) on viable  (TUNEL−) cells after culture. To  exclude the possibility that CD4  ligation during the panning procedure affected the results (50),  parallel experiments were performed with cells that were purified by methods that did not involve CD4 ligation, e.g., by  using unmanipulated thymocytes from β2m−/− mice as a  source of purified CD4+8+ cells  and CD8− IL-2R− normal thymocytes as an enriched source of  CD4+8− cells. The results obtained with these cells were essentially identical to the data  shown in Figs. 3 and 4.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2196120&req=5

Figure 2: Apoptosis of thymocyte subsets and LN T cells induced by stimulation with anti-TCR mAb or anti-TCR plus anti-CD28 mAbs in vitro. Purified populations of CD4+8+, HSAhi CD4+8−, and HSAlo CD4+8− thymocytes and CD4+8− LN cells were cultured for 20 h in vitro on plates coated with anti-TCR mAb alone (H57, 10 μg/ml) or with a mixture of anti-TCR (10 μg/ml) and anti-CD28 (20 μg/ml) mAbs. (A) The purity of the subsets before culture (left) and the extent of apoptosis determined by TUNEL staining after culture (right) are shown; for TUNEL staining, the forward scatter (FSC) profile shows the relative size of the cells. (B) Shows surface expression of CD69 and CD25 (IL-2R) on viable (TUNEL−) cells after culture. To exclude the possibility that CD4 ligation during the panning procedure affected the results (50), parallel experiments were performed with cells that were purified by methods that did not involve CD4 ligation, e.g., by using unmanipulated thymocytes from β2m−/− mice as a source of purified CD4+8+ cells and CD8− IL-2R− normal thymocytes as an enriched source of CD4+8− cells. The results obtained with these cells were essentially identical to the data shown in Figs. 3 and 4.
Mentions: To extend these findings, purified subsets of thymocytes were tested for their sensitivity to negative selection (apoptosis) mediated by cross-linked anti-TCR plus anti-CD28 mAbs in vitro; exposure to cross-linked anti-TCR mAb alone was used as a control. Apoptosis was measured by TUNEL staining after overnight culture. Fig. 2 shows the purity of the cells tested (A, left), TUNEL staining of the cultured cells (A, right), and the expression of two activation markers, CD69 and CD25 (IL-2R), on viable (TUNEL−) cells (B); cells were cultured on plates coated with anti-CD28 (20 μg/ml) and/or anti-TCR (10 μg/ml) mAbs. Fig. 3 A shows the effects of culturing the cells with decreasing concentrations of anti-TCR mAb ± a fixed concentration of anti-CD28 mAb (20 μg/ml); background levels of apoptosis found with cells cultured in medium alone have been subtracted, and the data are shown as change in apoptosis. The data in Figs. 2 and 3 A make three points (see Fig. 2, legend).

Bottom Line: However, being relatively mature, medullary T cells are thought to be beyond the stage of tolerance induction.These findings suggest that the differentiated T cells reaching the medulla from the cortex remain sensitive to tolerance induction for a brief period before acquiring a fully mature tolerance-resistant phenotype.The semimature subset of medullarsy T cells displays unique requirements for tolerance induction; depending upon the conditions used, tolerizing these cells can involve either a Fas (CD95)-dependent or a Fas-independent pathway.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, IMM4, The Scripps Research Institute, La Jolla, California 92037, USA.

ABSTRACT
The thymic medulla plays a key role in negative selection (self-tolerance induction) and contains differentiated T cells en route to the extrathymic environment. However, being relatively mature, medullary T cells are thought to be beyond the stage of tolerance induction. This paradox is resolved by the finding that medullary T cells (CD4+8- thymocytes) comprise two distinct subsets. Medullary thymocytes expressing a fully mature (HSAlo) phenotype are strongly resistant to tolerance induction, whereas cells with a semimature (HSAhi) phenotype are tolerance susceptible. These findings suggest that the differentiated T cells reaching the medulla from the cortex remain sensitive to tolerance induction for a brief period before acquiring a fully mature tolerance-resistant phenotype. The semimature subset of medullarsy T cells displays unique requirements for tolerance induction; depending upon the conditions used, tolerizing these cells can involve either a Fas (CD95)-dependent or a Fas-independent pathway.

Show MeSH
Related in: MedlinePlus