LPS-nonresponsive variants of mouse B cell lymphoma, 70Z/3: isolation and characterization

Area of Science:

• Immunology
• Cell Biology
• Genetics

Background:

• The murine cell line 70Z/3 mimics pre-B cells, expressing internal immunoglobulin heavy chain (IgM, mu) but lacking light chain (L).
• Activation with B cell mitogen lipopolysaccharide (LPS) normally induces 70Z/3 cells to mature into B lymphocytes, expressing surface IgM and L chain.

Purpose of the Study:

• To investigate the genetic basis of B lymphocyte differentiation using the 70Z/3 cell line.
• To identify mutations affecting the response to lipopolysaccharide (LPS)-induced differentiation.

Main Methods:

• Utilized immunoselection against surface-bound IgM to isolate LPS-uninducible variants of the 70Z/3 cell line.
• Characterized variants by their response to LPS stimulation and assessed for structural defects.

Main Results:

• Two complementation groups of LPS-uninducible variants, designated LPS A and LPS B, were identified.
• LPS A variants (1/1200 frequency) were completely unresponsive to LPS. LPS B variants showed a subset of cells inducible for surface IgM, with induction increasing upon prolonged LPS exposure.
• No structural defects were found in either variant group.

Conclusions:

• LPS A variants likely harbor mutations in genes essential for LPS-mediated signaling or differentiation.
• LPS B variants may possess a defect in the decision-making process for LPS-induced B cell differentiation.