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V(H) replacement in rearranged immunoglobulin genes
1Department of Immunology, Division of Immunology, Infection and Inflammation, University of Glasgow, Western Infirmary, Glasgow, UK. john.m.darlow@clinmed.gla.ac.uk
Immunology
|January 26, 2005
Summary
Two types of V(H) segment replacement in immunoglobulin genes are reviewed. One type, involving RAG proteins, is accepted, while the second, potentially AID-mediated, requires further validation due to PCR artifact concerns.
Area of Science:
- Immunology
- Molecular Biology
- Genetics
Background:
- Since the 1980s, evidence has emerged for V(H) segment replacement in rearranged V(H)DJ(H) genes.
- Two distinct mechanisms of V(H) replacement have been proposed, with differing levels of acceptance.
Purpose of the Study:
- To review and critically examine the evidence for two types of V(H) segment replacement.
- To differentiate between established mechanisms and those requiring further validation.
Main Methods:
- Review of existing scientific literature and published sequence data.
- Critical analysis of evidence, distinguishing between biological mechanisms and potential experimental artifacts (e.g., PCR).
Main Results:
- One type of V(H) replacement, involving RAG proteins and recombination signal sequences (RSS) in immature B cells, is well-established.
- A second proposed mechanism, potentially involving activation-induced cytidine deaminase (AID) in hypermutating cells, is critically evaluated.
- Re-examination of sequences reveals AID target sites and gene conversion-like events in V(H)-V(H) junctions, supporting the second mechanism but highlighting the need to exclude artifacts.
Conclusions:
- The RAG-mediated V(H) replacement is a validated process in B cell development.
- The AID-mediated V(H) replacement requires further rigorous evidence to distinguish it from polymerase chain reaction (PCR) artifacts.