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Updated: Aug 9, 2026

Induction and Assessment of Class Switch Recombination in Purified Murine B Cells
09:49

Induction and Assessment of Class Switch Recombination in Purified Murine B Cells

Published on: August 14, 2010

Cell-free recombination of immunoglobulin switch-region DNA with nuclear extracts

K Zhang1, H K Cheah

  • 1The Hart and Louise Lyon Laboratory, UCLA School of Medicine, Los Angeles, California 90095-1680, USA. kzhang@mednet.ucla.edu

Clinical Immunology (Orlando, Fla.)
|January 19, 2000
PubMed

Insights

Researchers created an in vitro system using human B lymphocyte extracts to study immunoglobulin (Ig) class switch recombination. This system successfully replicated key features of Ig isotype switching, offering a new tool for allergy research.

Area of Science:

  • Immunology
  • Molecular Biology
  • Genetics

Background:

  • Immunoglobulin (Ig) class switch recombination (CSR) is a critical process in adaptive immunity.
  • CSR enables B cells to produce antibodies of different effector functions.
  • Understanding the molecular mechanisms of CSR, particularly IgE class switch recombination, is vital for addressing allergic diseases.

Purpose of the Study:

  • To develop and validate an in vitro system for studying Ig switch-region DNA recombination.
  • To investigate the role of cell-free nuclear extracts from human B lymphocytes in mediating recombination between Smu and Sepsilon sequences.
  • To characterize the features of this in vitro recombination system and its potential for dissecting IgE CSR.

Main Methods:

  • Development of an in vitro recombination assay using cell-free nuclear extracts from human B lymphocytes.
  • Employing a model plasmid containing human mu switch (Smu) and Sepsilon sequences.
  • Analysis of recombination products through amplification prior to bacterial transformation.
  • Characterization of recombination specificity, mechanism (nonhomologous), and dependence on CD40 stimulation.

Main Results:

  • The cell-free nuclear extracts successfully mediated recombination between Smu and Sepsilon sequences.
  • Nuclear extracts from CD40-stimulated B lymphocytes showed a higher recombination frequency compared to unstimulated cells.
  • The observed recombination exhibited characteristics of Ig isotype switching: switch-region-sequence specificity, nonhomologous recombination, and enhancement by CD40 stimulation.
  • Transcription through the S region DNA was not necessary for recombination in this system.

Conclusions:

  • Ig switch-region DNA recombination can be effectively accomplished in vitro using cell-free nuclear extracts.
  • This novel in vitro system provides a powerful tool for dissecting the molecular events underlying IgE class switch recombination.
  • The findings pave the way for further investigation into the mechanisms of IgE CSR, crucial for understanding and potentially treating allergic diseases.

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