Bibliographic record
Abstract
signaling in the thymus.However, it did not exclude the possibility that both T-restricted and B-restricted progenitors could already be present in the thymus and that the absence of Notch signaling merely allowed B-cell-restricted progenitors to develop.In this issue of Blood, Harman and colleagues elegantly redefine the site where Notch signaling determines lineage choice.By developing a technique that permits microdissection of fetal thymic rudiments, they were able to separate perithymic mesenchyme from the intraepithelial regions of the thymus.This allowed comparison of precursors both before and after contact with the Notch ligands expressed on thymic epithelial cells without the involvement of more mature cells from the circulation.The authors show that progenitors isolated from the epithelial region can give rise to only T cells.This is in marked contrast to progenitors from fetal liver, which could generate both T and B cells.In fact, only progenitor cells isolated from fetal liver were able to give rise to B cells (see the figure).This shows that the decision to become a T cell occurs in fetal liver, prior to entry into the thymus.It does not exclude a role for Notch signaling in this decision; indeed, Harman et al show that Notch signaling occurs in fetal liver progenitors and suggest that further Notch signaling in the thymus reveals this choice.In a further development, Dallas et al 5 have recently shown that the density of the Notch ligand, Delta-like 1, determines the generation of B-and T-cell precursors from hematopoietic cells with low densities promoting both Band T-cell precursor development and high densities promoting only T-cell precursor development.This correlates with the expression of Delta-like 1 shown by Harman et al.Delta-like 1 is the predominant Notch ligand expressed by fetal liver stromal cells.Thus, the density of Delta-like 1 expressed in extrathymic sites may be a key determinant in the T-/B-cell lineage choice.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".