The switch from IgM to IgG secretion in single mitogen-stimulated B-cell clones

Area of Science:

• Immunology
• Cell Biology

Background:

• B cells are crucial for adaptive immunity, producing antibodies to combat pathogens.
• Antibody class switching, from IgM to IgG, is a key process for immune response diversification.

Purpose of the Study:

• To determine the frequency of B cells that develop into IgG-secreting cells.
• To investigate the developmental relationship between IgM- and IgG-secreting B cell clones.

Main Methods:

• Limiting dilution analysis of mitogen-reactive B cells in mouse spleen.
• In vitro culture to allow B cell growth and differentiation into Ig-secreting cells.
• Assay of cultures for IgM and IgG plaque-forming cells (PFCs) at different time points.

Main Results:

• Frequencies of IgG precursor cells were 1 in 30 to 1 in 40 B cells, one-tenth of IgM precursor frequencies.
• All IgG-secreting cell clones originated from precursors that also generated IgM-secreting cells.
• Statistical analysis showed a highly significant probability that IgG and IgM secretion arose from the same precursor.

Conclusions:

• The majority of IgG-secreting cells in mitogen-stimulated B cell clones develop via a switch from IgM secretion.
• IgG secretion can occur at various stages of B cell clonal expansion.
• The switch to IgG is a dynamic process within a single B cell clone.