The role of the B cell receptor complex in avian B cell development dissected by retroviruses /
Bibliographic record
Abstract
During embryogenesis, B cell precursors that have undergone productive Ig V(D)J rearrangement are selected to expand in oligoclonal follicles of the bursa of Fabricius. Because Ig V(D)J recombination in chickens results in minimal diversity, diversity being generated instead by gene conversion in the follicles of the bursa of Fabricius, B cell precursors express a limited range of Ig specificities prior to colonization of the bursa. It has been proposed that recognition of endogenous ligands by this 'pre-diversified' B cell receptor is critical to the progression of normal B cell development. To test this hypothesis, we constructed a truncated IgM receptor (Tmu) lacking the V and Cmu1 domain, which does not associate with Ig L chain proteins nor does it require IgL chains for surface expression, and used a retroviral gene transfer system to introduce it in developing chick embryos. In these embryos, Tmu+ B cell precursors productively colonized bursal follicles as efficiently as B cell precursors expressing endogenous sIg. Furthermore, we detected low but significant levels of IgL VJ rearrangements in Tmu + bursal cells. The analysis of these VJ junctions revealed no selection for in-frame products as these cells are maintained by the Tmu receptor. Interestingly, we showed that the rearranged VL segments derived from Tmu+ bursal cells underwent gene conversion indistinguishably from rearranged VL segments derived from bursal cells expressing endogenous sIg. Taken together, we have ruled out a role for V(D)J encoded determinants in the normal development of B cells in avian embryos. Sequence analysis of 80 IgL VJ segments derived from Tmu+ bursal allowed the unique opportunity to assess the efficiency of gene conversion in vivo, in the absence of selection. Using this system, we demonstrated that >97% of gene conversion events maintain the sequence in-frame. Following hatching, the bursa undergoes morphological changes initiated by the migration of bursal cells ba
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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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".