The impact of negative selection on thymocyte migration in the medulla

Borgne, Marie Le; Ladi, Ena; Dzhagalov, Ivan; Herzmark, Paul; Liao, Ying Fang; Chakraborty, Arup K.; Robey, Ellen

doi:10.1038/ni.1761

Cited by 128 publications

(139 citation statements)

References 39 publications

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“…High motility is a consistent feature of SP thymocytes in the medulla (6,25,34,35) and mature T cells in lymph nodes (36), implying that increased motility reflects long-lasting changes in the cellular machinery that controls migration, rather than a short-term response to a chemokine gradient. Consistent with this notion, gene-expression studies of pre-and postselection DP thymocytes revealed induction of numerous genes that may play a role in regulating cell adhesion, metabolism, and the cytoskeleton (37)(38)(39).…”

Section: Discussionmentioning

confidence: 97%

Distinct phases in the positive selection of CD8⁺T cells distinguished by intrathymic migration and T-cell receptor signaling patterns

Ross

Melichar

Au-Yeung

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Positive selection of CD8 T cells in the thymus is thought to be a multistep process lasting 3-4 d; however, the discrete steps involved are poorly understood. Here, we examine phenotypic changes, calcium signaling, and intrathymic migration in a synchronized cohort of MHC class I-specific thymocytes undergoing positive selection in situ. Transient elevations in intracellular calcium concentration ([Ca 2+ ] i ) and migratory pauses occurred throughout the first 24 h of positive selection, becoming progressively briefer and accompanied by a gradual shift in basal [Ca 2+ ] i over time. Changes in chemokine-receptor expression and relocalization from the cortex to medulla occurred between 12 and 24 h after the initial encounter with positive-selecting ligands, a time frame at which the majority of thymocytes retain CD4 and CD8 expression and still require T-cell receptor (TCR) signaling to efficiently complete positive selection. Our results identify distinct phases in the positive selection of MHC class I-specific thymocytes that are distinguished by their TCR-signaling pattern and intrathymic location and provide a framework for understanding the multistep process of positive selection in the thymus.Zap70 | thymic slice | two photon microscopy D eveloping thymocytes test their newly formed T-cell antigen receptors (TCRs) for their ability to bind self-peptide:major histocompatibility complex (MHC) complexes on thymic support cells. This process encompasses both positive and negative selection and ultimately leads to the formation of a functional and self-tolerant mature T-cell repertoire. During positive selection, CD4 + CD8 + [double positive (DP)] thymocytes with TCRs weakly reactive to self-peptide:MHC complexes receive signals to survive, mature, and give rise to CD4 or CD8 single positive (SP) cells. Positive selection requires close contact with thymic stromal cells and occurs over a period of several days (1-4). However, much of our information about T-cell development is based on analyses of steady-state thymocyte populations, and the individual steps that occur during the prolonged process of positive selection remain obscure.Thymocytes are highly motile within three-dimensional thymic tissue environments, and positive selection is tightly linked to thymocyte migration. The initial encounters with positive-selecting ligands on cortical thymic epithelial cells do not induce strong migratory stop signals, but instead occur as brief migratory pauses associated with transient elevations in intracellular calcium concentration ([Ca 2+ ] i ) (5-7). These brief, serial TCR signals are consistent with indications that positive selection is driven by weak recognition of self-peptide:MHC complexes and with the unique ability of DP thymocytes to respond to low-potency ligands (8, 9). However, there are also indications that thymocytes that have already received TCR signals still require further signaling to complete positive selection (10, 11). Thus, although the encounters with positive-selecting ligands last for...

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Section: Discussionmentioning

confidence: 97%

Distinct phases in the positive selection of CD8⁺T cells distinguished by intrathymic migration and T-cell receptor signaling patterns

Ross

Melichar

Au-Yeung

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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“…One possible explanation for this could be that the requirements for scanning and pMHC contacts are less stringent for negative selection than for positive selection. Negative selection in the medulla requires regulation of thymocyte migration patterns (7,33), and thymocytes spend about twice as much time undergoing negative selection (4-5 d) than positive selection in the cortex (2-3 d) (34). If the increased migration of aPix 2 thymocytes results in inefficient, error-prone scanning for pMHC, then the extra time thymocytes spend in the medulla can compensate for their poor performance.…”

Section: Discussionmentioning

confidence: 99%

“…If the increased migration of aPix 2 thymocytes results in inefficient, error-prone scanning for pMHC, then the extra time thymocytes spend in the medulla can compensate for their poor performance. In addition, self-peptides in the medulla induce repeated encounters between thymocytes and mTECs and DCs in confined areas (33), which might ensure that aPix 2 thymocytes would eventually encounter any autoactivating peptides. The normal negative selection we observed in the aPix 2 thymus was supported by a lack of evidence of autoimmune disease in these mice, in contrast to CCR7 knockout mice that exhibit extensive autoimmune pathologies (35).…”

Section: Discussionmentioning

confidence: 99%

αPIX RhoGEF Supports Positive Selection by Restraining Migration and Promoting Arrest of Thymocytes

Korthals

Schilling

Reichardt

et al. 2014

The Journal of Immunology

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Thymocytes mature in a series of stages by migrating through specific areas of the thymus and interacting with other cells to receive the necessary developmental signals; however, little is known about the molecular mechanisms governing this migration. We report that murine thymocytes with a knockout mutation in α-PAK (p21-activated kinase)-interacting exchange factor (PIX; Arhgef6), an activator of Rho GTPases, showed greatly increased motility and altered morphology in two-dimensional migration on ICAM-1. αPIX was also required for efficient positive selection, but not negative selection, of thymocytes. TCR signaling was normal in αPix− thymocytes, indicating that the effects of αPIX on positive selection are largely independent of TCR signaling. αPix− thymocytes also paused less during migration in the thymic cortex, interacted less with ICAM-1 coated beads, and could overcome TCR stop signals, consistent with defective scanning behavior. These results identify αPIX as a regulator of thymocyte migration and subsequent arrest that is linked to positive selection.

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“…One of the central questions in this field is whether migration is best described as a (persistent) random walk or whether directed or confined migration is involved, because this is important for our understanding of how cells manage to carry out their functions. Examples of persistent random walk include the migration of T cells, B cells, and plasma cells in lymph nodes (2, 6-8) and of effector T cells migrating in tumors (9), whereas nonrandom migration has for instance been discovered in antigen-engaged B cells moving toward the T zone boundary early in a B-cell response (10), CD8 + T cells being attracted toward "licensed" dendritic cells (11)(12)(13)(14), neutrophil movement in skin (15, 16), and during thymocyte maturation (17,18).In some applications, it is controversial whether migration is best described as random or not, and a prime example is B-cell migration in germinal centers (GCs). At these sites, B lymphocytes mature by somatic hypermutation and clonal selection of the mutants that produce antibody of high affinity.…”

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B cells within germinal centers migrate preferentially from dark to light zone

Beltman

Allen

Cyster

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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One of the main questions in the field of imaging immune cell migration in living tissues is whether cells fulfill their functionality via random or nonrandom migration processes. For some applications, this issue has remained controversial even after publication of various imaging studies. A prime example is B-cell migration in germinal centers (GCs) where somatic hypermutation and clonal selection of B cells are thought to occur within morphologically distinct regions termed dark zone (DZ) and light zone (LZ). Here, we reanalyze a previously published dataset on GC B-cell migration, applying a sensitive analysis technique to detect directed migration and using a procedure to correct for a number of artifacts that frequently occur in time-lapse imaging experiments. Although B cells roughly perform a persistent random walk, we present evidence that they have a small preference (of on average about 0.2−0.3 μm min −1 ) to migrate from DZ to LZ, which is consistent with classical views of the GC reaction. This preference is most pronounced among a large subset of almost half of the B-cell population migrating along relatively straight tracks. Using a computational model to generate long-lasting B-cell tracks based on the experimental motility data (including the small directional preference), we predict a time course to travel from DZ to LZ of a few hours. This is consistent with experimental observations, and we show that at the observed cellular motility such a time course cannot be explained without the small preferential migration from DZ to LZ.B-cell motility | cyclic reentry | two-photon microscopy T hanks to the application of two-photon microscopy to living lymphoid tissues, an exciting glimpse of how the migration of various types of immune cells takes place was recently obtained (1-5). One of the central questions in this field is whether migration is best described as a (persistent) random walk or whether directed or confined migration is involved, because this is important for our understanding of how cells manage to carry out their functions. Examples of persistent random walk include the migration of T cells, B cells, and plasma cells in lymph nodes (2, 6-8) and of effector T cells migrating in tumors (9), whereas nonrandom migration has for instance been discovered in antigen-engaged B cells moving toward the T zone boundary early in a B-cell response (10), CD8 + T cells being attracted toward "licensed" dendritic cells (11)(12)(13)(14), neutrophil movement in skin (15, 16), and during thymocyte maturation (17,18).In some applications, it is controversial whether migration is best described as random or not, and a prime example is B-cell migration in germinal centers (GCs). At these sites, B lymphocytes mature by somatic hypermutation and clonal selection of the mutants that produce antibody of high affinity. These two processes are thought to occur in morphologically distinct regions termed dark zone (DZ) and light zone (LZ), but in the literature competing views exist on the functional meaning of D...

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The impact of negative selection on thymocyte migration in the medulla

Cited by 128 publications

References 39 publications

Distinct phases in the positive selection of CD8⁺T cells distinguished by intrathymic migration and T-cell receptor signaling patterns

Distinct phases in the positive selection of CD8⁺T cells distinguished by intrathymic migration and T-cell receptor signaling patterns

αPIX RhoGEF Supports Positive Selection by Restraining Migration and Promoting Arrest of Thymocytes

B cells within germinal centers migrate preferentially from dark to light zone

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The impact of negative selection on thymocyte migration in the medulla

Cited by 128 publications

References 39 publications

Distinct phases in the positive selection of CD8+T cells distinguished by intrathymic migration and T-cell receptor signaling patterns

Distinct phases in the positive selection of CD8+T cells distinguished by intrathymic migration and T-cell receptor signaling patterns

αPIX RhoGEF Supports Positive Selection by Restraining Migration and Promoting Arrest of Thymocytes

B cells within germinal centers migrate preferentially from dark to light zone

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Distinct phases in the positive selection of CD8⁺T cells distinguished by intrathymic migration and T-cell receptor signaling patterns

Distinct phases in the positive selection of CD8⁺T cells distinguished by intrathymic migration and T-cell receptor signaling patterns