Regulation of TLR Expression and Activation in Human Mesenchymal Stromal Cells by IFN-a, IFN-g and TNF-a.
Bibliographic record
Abstract
Abstract Members of the toll-like receptor (TLR) family bind to pathogen-associated molecular patterns and subsequently induce the activation of the innate and adaptive immune responses. We investigated here the expression and role of TLRs in mesenchymal stromal cells (MSC), which are bone marrow-derived mesenchymal progenitors with recently described antigen presenting cell (APC) properties [Stagg et al, Blood (March 2006), Romieu et al., JI (in press)]. We observed that human MSCs express basal levels of TLR3 and TLR4, and these responded to their respective ligands, e.g. polycytidylic acid (poly I:C) or lipopolysaccharide (LPS), by the production of IL-6, IL-8 and IL-1b but not of active IL-12 p70 dimer. Exposure of MSCs to TNF-a increased the expression of TLR2 and TLR4 while IFN-a strongly upregulated TLR3 expression. By contrast, IFN-g had only a marginal effect on the expression of any TLR. IFN-a and poly I:C, as well as IFN-g and poly I:C or LPS were observed to work in synergy for the up-regulation of expression of several cytokines or inflammatory mediators, such as IL-12 p35 (IL-12A), TNF-a, RANTES, TRAIL, IFN-b and NOS2A in MSC. In contrast, none of these treatments induced the upregulation of IL-12 p40 (IL-12B), which may explain the lower levels of IL-12 p70 produced in MSCs compared to primary macrophages. Since c-Rel/p50 NF-kB dimers as well as IFN-induced IRF-1 were shown to control IL-12B and/or IL12A promoters, respectively, we next investigated expression of these transcription factors in MSCs. Results showed that MSC expressed the ubiquitous RelA NF-kB subunit but displayed significantly lower expression of c-Rel compared to macrophages. IRF-1 was upregulated following treatments with IFN-g or, to a lesser extent, with IFN-a. Therefore, the lower levels of IL-12 p70 seen in MSCs compared to macrophages may be explained by the absence of c-Rel in MSCs, which hinders the upregulation of IL-12A and IL-12B after exposure to single TLR ligands. However, the induction of IRF-1 by IFN-g or IFN-a may explain the synergistic effect observed in the upregulation of IL-12A in MSC treated with IFN-g or IFN-a and TLR ligands. In conclusion, TLR expression in human MSCs plays a role in their immune activation, although the outcome of this activation is different from the result of macrophage activation by TLR.
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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) | 0.000 | 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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".