A Crystal Structure of the Complex Between Human Complement Receptor 2 and Its Ligand C3d
Bibliographic record
Abstract
The interaction of complement receptor 2 (CR2)--which is present on B cells and follicular dendritic cells--with its antigen-bound ligand C3d results in an enhanced antibody response, thus providing an important link between the innate and adaptive immune systems. Although a cocrystal structure of a complex between C3d and the ligand-binding domains of CR2 has been published, several aspects of this structure, including the position in C3d of the binding interface, remained controversial because of disagreement with biochemical data. We now report a cocrystal structure of a CR2(SCR1-2):C3d complex at 3.2 angstrom resolution in which the interaction interfaces differ markedly from the previously published structure and are consistent with the biochemical data. It is likely that, in the previous structure, the interaction was influenced by the presence of zinc acetate additive in the crystallization buffer, leading to a nonphysiological complex. Detailed knowledge of the binding interface now at hand gives the potential to exploit the interaction in vaccine design or in therapeutics directed against autoreactive B cells.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".