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Transcript expression of two Iglambda rearrangements and RAG-1/RAG-2 in a mature human B cell producing IgMlambda
Carmen Benito1, Ramon Gomis, Josefa Fernández-Alvarez
1Endocrinology and Diabetes Service, Hospital Clínic Universitari, IDIBAPS, Faculty of Medicine, University of Barcelona, Villarroel 170, 08036 Barcelona, Spain.
Journal of Clinical Immunology
|May 22, 2003
Summary
This study analyzed B cell clones from a Type 1 diabetic child, revealing a unique immunoglobulin lambda rearrangement associated with autoantibody production. Aberrant gene rearrangements impacted antibody secretion and cell viability, suggesting complex B cell dynamics in autoimmunity.
Area of Science:
- Immunology
- Molecular Biology
- Genetics
Background:
- Human B cell clones producing islet cell autoantibody (ICA) are crucial for understanding Type 1 diabetes pathogenesis.
- Epstein-Barr virus (EBV) transformation is a method to immortalize B cells for studying autoimmune responses.
Purpose of the Study:
- To analyze the rearranged immunoglobulin (Ig) genes in an EBV-transformed B cell clone (EBV-MB91) and its derived heterohybridoma (HY-MB91) producing IgMlambda-ICA.
- To investigate the role of specific Ig lambda chain rearrangements in ICA secretion and B cell survival.
Main Methods:
- Analysis of rearranged Ig heavy and lambda light chain genes in EBV-MB91 and HY-MB91.
- Quantification of Ig lambda chain transcripts using RT-PCR.
- Assessment of RAG-1 and RAG-2 transcript expression.
Main Results:
- Both clones expressed a unique, unmutated IgH chain rearrangement.
- Two Ig lambda chain rearrangements were identified: a productive Vlambda1-4-Jlambda3-Clambda3 and a non-productive Vlambda4-1-Jlambda3-Clambda3 with stop codons.
- Loss of IgMlambda-ICA secretion in HY-MB91 correlated with the predominance of aberrant Vlambda4-1-Jlambda3-Clambda3 transcripts.
- EBV-MB91 showed loss of secretion and cell death, with detectable RAG-1 and RAG-2 transcripts.
Conclusions:
- Mature B cells producing autoantibodies can express RAG-1/RAG-2 transcripts, suggesting potential for V(D)J recombinase activity.
- The aberrant Vlambda4-1-Jlambda3-Clambda3 rearrangement may represent a non-productive event at the pre-B cell stage or a secondary rearrangement in the mature B cell.
- These findings shed light on the complex genetic mechanisms underlying autoantibody production in Type 1 diabetes.