Toll-Like Receptor 4/Stem Cell Antigen 1 Signaling Promotes Hematopoietic Precursor Cell Commitment to Granulocyte Development during the Granulopoietic Response to Escherichia coli Bacteremia
Bibliographic record
Abstract
In response to severe bacterial infection, bone marrow hematopoietic activity shifts toward promoting granulopoiesis. The underlying cell signaling mechanisms remain obscure. To study the role of Toll-like receptor 4 (TLR4)/stem cell antigen-1 (Sca-1) signaling in this process, bacteremia was induced in mice by intravenous injection of Escherichia coli. A subgroup of animals also received intravenous 5-bromo-2-deoxyuridine (BrdU). In a separate set of experiments, bone marrow lineage-negative (lin(-)) stem cell growth factor receptor-positive (c-kit(+)) Sca-1(-) cells containing primarily common myeloid progenitors were cultured in vitro without or with E. coli lipopolysaccharide (LPS). In genotypic background control mice, bacteremia significantly upregulated Sca-1 expression by lin(-) c-kit(+) cells, as reflected by a marked increase in BrdU-negative lin(-) c-kit(+) Sca-1(+) cells in the bone marrow. In mice with the TLR4 gene deletion, this bacteremia-evoked Sca-1 response was blocked. In vitro, LPS induced a dose-dependent increase in Sca-1 expression by cultured marrow lin(-) c-kit(+) Sca-1(-) cells. LPS-induced upregulation of Sca-1 expression was regulated at the transcriptional level. Inhibition of c-Jun N-terminal kinase/stress-activated protein kinase (JNK) activity with the specific inhibitor SP600125 suppressed LPS-induced upregulation of Sca-1 expression by marrow lin(-) c-kit(+) Sca-1(-) cells. Engagement of Sca-1 with anti-Sca-1 antibodies enhanced the expression of Sfpi1 spleen focus-forming virus (SFFV) proviral integration 1 (PU.1) in marrow lin(-) c-kit(+) Sca-1(-) cells cultured with LPS. Sca-1 null mice failed to maintain the marrow pool of granulopoietic cells following bacteremia. These results demonstrate that TLR4/Sca-1 signaling plays an important role in the regulation of hematopoietic precursor cell programming and their enhancement of granulocyte lineage commitment in response to E. coli bacteremia.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 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 source (direct Gemma or distilled Codex), 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".