Abnormal response to a human B cell growth factor in patients with common variable immunodeficiency (CVI)

Area of Science:

• Immunology
• Molecular Biology

Background:

• Common Variable Immunodeficiency (CVI) is characterized by impaired antibody production, specifically a failure to generate antigen-specific IgG.
• High Molecular Weight B Cell Growth Factor (HMW BCGF) is a lymphokine known to expand IgG-producing B cell subpopulations.

Purpose of the Study:

• To investigate the B cell response to HMW BCGF in patients with CVI.
• To explore the underlying molecular mechanisms for the B cell dysfunction in CVI.

Main Methods:

• Assessed B cell proliferation in response to HMW BCGF and low molecular weight BCGF (LMW BCGF).
• Quantified HMW BCGF receptor expression on CVI B cells.
• Measured intracellular signaling molecules (cyclic adenosine monophosphate, phosphoinositides) following HMW BCGF stimulation.

Main Results:

• B cells from 15 of 16 CVI patients failed to proliferate in response to HMW BCGF, but responded normally to LMW BCGF.
• Elevated baseline levels of cytoplasmic phosphoinositides were observed in CVI B cells.
• CVI B cells did not show significant increases in cyclic adenosine monophosphate or phosphoinositides after HMW BCGF stimulation.

Conclusions:

• The unresponsiveness of CVI B cells to HMW BCGF may stem from abnormal in vivo activation.
• This cellular defect could explain the impaired secondary antibody responses seen in CVI patients.
• HMW BCGF's role in expanding memory B cells highlights a potential mechanism for CVI pathogenesis.