Molecular and Cellular Properties of the Rat AA4 Antigen, a C-type Lectin-like Receptor with Structural Homology to Thrombomodulin
Bibliographic record
Abstract
The murine fetal stem cell marker AA4 has recently been cloned and is known to be the homolog of the human phagocytic C1q receptor involved in host defense. We herein report the molecular cloning and the cellular expression pattern of the rat AA4 antigen. Modular architecture analysis indicated that the rat AA4 is a member of C-type lectin-like family and, interestingly, displays similar domain composition and organization to thrombomodulin. Northern blot and reverse transcriptase-polymerase chain reaction analyses indicated that rat AA4 was encoded by a single transcript of 7 kilobases expressed constitutively in all tissues. In situ hybridization showed that AA4 was expressed predominantly by pneumocytes and vascular endothelial cells. Using an affinity purified polyclonal antibody raised against a rat AA4-Fc fusion protein, AA4 was identified as a glycosylated protein of 100 kDa expressed by endothelial cells > platelets > NK cells and monocytes (ED1+ cells). The staining was associated to the cell surface and intracytoplasmic vesicles. Conversely, erythrocytes, T and B lymphocytes, neutrophils, and macrophages (ED2+ cells) were consistently negative for AA4. As expected, the macrophage cell line NR8383 expressed weak levels of AA4. Taken together, our results support the idea that AA4/C1qRp is involved in some cell-cell interactions.
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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 | 0.000 |
| 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".