Phosphatidylcholine as a metabolic cue for determining B cell fate and function

Area of Science:

• Immunology
• Cell Biology
• Biochemistry

Background:

• Activated B cells increase phosphatidylcholine (PtdCho) production via the CDP-choline pathway.
• CTP:phosphocholine cytidylyltransferase α (CCTα) is the rate-limiting enzyme in PtdCho synthesis.
• PtdCho synthesis is implicated in germinal center reactions and B cell fate.

Purpose of the Study:

• To investigate the role of PtdCho in B cell fate during germinal center responses.
• To assess the impact of disrupted PtdCho synthesis on B cell class switch recombination and antibody production.

Main Methods:

• Generated mice with B cell-specific disruption of PtdCho synthesis, specifically in IgG1-expressing B cells.
• Analyzed serum immunoglobulin levels (IgM, IgG subclasses) in naïve and immunized mice.
• Quantified antigen-specific B cells and antibody-secreting cells (ASCs) in spleen and bone marrow.

Main Results:

• Reduced serum IgG1, IgG2b, and IgG anti-NP antibody titers in mice with disrupted PtdCho synthesis.
• Decreased frequency of NP-specific IgG antibody-secreting cells in spleen and bone marrow.
• Reduced frequency and number of IgG1 NP-specific B cells, particularly in Cγ1^Cre/Cre mice.

Conclusions:

• Phosphatidylcholine synthesis is essential for the generation of germinal center-derived B cells and antibody-secreting cells.
• Antibody-secreting cells exhibit a higher demand for PtdCho compared to germinal center B cells.
• PtdCho is critical for effective humoral immune responses, particularly IgG production.