The Role of TLR2 In Vivo following Challenge with <i>Staphylococcus aureus</i> and Prototypic Ligands
Bibliographic record
Abstract
Based on a wealth of in vitro macrophage studies, immunity to Staphylococcus aureus cell wall-derived peptidoglycan (PGN) and lipoteichoic acid has been attributed to TLR2. We investigated whether the in vitro paradigm of TLR2 dominance would hold true in vivo. Using an experimental peritonitis model, we challenged mice with PGN or lipoteichoic acid and found that only PGN resulted in significant leukocyte (primarily neutrophil) accumulation in the peritoneum at 4 h. PGN-mediated leukocyte recruitment was P-/E-selectin dependent but only partially TLR2 dependent, and also involved the C5aR. Concomitant inhibition of TLR2 and C5aR resulted in a further reduction in PGN-induced peritonitis. Peritoneal neutrophilia was partially mast cell dependent; however, the defect could not be reconstituted with TLR2(-/-) or C5aR(-/-) mast cells. Interestingly, macrophage-deficient mice did not have defective neutrophil recruitment. By 24 h, the response to PGN involved primarily monocytes and was TLR2 and C5aR independent. Finally, we challenged mice with live S. aureus and found a similar degree of TLR2 involvement in leukocyte recruitment to that observed with PGN. Most importantly, bacterial clearance from the spleen and peritoneum was not altered in TLR2(-/-) mice vs wild-type mice. Morbidity was only significantly increased in S. aureus-infected mice treated with a blocking Fab against C5aR. Taken together, these studies indicate that in vivo responses to prototypic TLR2 ligands do not necessarily recapitulate the absolute necessity for TLR2 observed in vitro, and additional receptors contribute, in a significant manner, to PGN and S. aureus-mediated immune responses.
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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 | 0.001 | 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".