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Decreased surface IgM receptor-mediated activation of phospholipase C gamma 2 in B-1 lymphocytes

D L Morris1, T L Rothstein

  • 1Department of Medicine, Boston University Medical Center Hospital, MA 02118.

International Immunology
|July 1, 1994
PubMed

Insights

Primary B-1 cells show impaired cell cycle progression due to a signaling block. This study reveals phospholipase C gamma 2 activation failure in B-1 cells, impacting signal propagation.

Area of Science:

  • Immunology
  • Cell Biology
  • Molecular Signaling

Background:

  • B-1 lymphocytes (CD5+ B cells) exhibit insufficient intracellular signaling for cell cycle progression.
  • A block in signal propagation before protein kinase C activation is suspected in B-1 cells.

Purpose of the Study:

  • To investigate proximal intracellular signaling elements in B-1 cells.
  • To identify the basis for aberrant signal transduction in B-1 lymphocytes.

Main Methods:

  • Analysis of src kinase composition.
  • Assessment of receptor-mediated tyrosine phosphorylation.
  • Evaluation of phospholipase C gamma 2 (PLCγ2) tyrosine phosphorylation and enzymatic activity after surface immunoglobulin (Ig) ligation.

Main Results:

  • No alterations in src kinase composition or diminished tyrosine phosphorylation were observed in B-1 cells.
  • PLCγ2 was inducibly tyrosine phosphorylated in B-1 cells upon surface Ig ligation.
  • Receptor-mediated PLCγ2 enzymatic activity was significantly reduced in B-1 cells compared to B-2 cells.

Conclusions:

  • PLCγ2 activation is largely impaired following surface Ig receptor engagement in B-1 cells.
  • Defective PLCγ2 activation may control signal propagation and cell cycle progression in B-1 lymphocytes.

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