Requirement for BAFF and APRIL during B cell development in GALT

Area of Science:

• Immunology
• Mammalian B cell development
• Lymphocyte biology

Background:

• B cell-activating factor (BAFF) and its role in B cell maturation and survival are well-studied in mice.
• The function of BAFF in B cell development in other mammals, like rabbits utilizing GALT, remains largely unknown.

Purpose of the Study:

• To investigate the expression and necessity of BAFF and APRIL in peripheral B cell development in young rabbits.
• To elucidate the role of BAFF and APRIL in GALT-dependent B cell development.

Main Methods:

• Neutralization of BAFF and APRIL in neonatal rabbits using a soluble decoy receptor (TACI-Fc).
• Analysis of peripheral B cell counts and bone marrow compartments.
• Assessment of B cell follicle size and proliferation in the appendix.

Main Results:

• Neutralization of BAFF and APRIL led to a significant decrease in peripheral B cells but no change in bone marrow B cells.
• B cell follicle size and proliferation were markedly reduced in the appendix.
• Rabbit B cells express BAFF receptor 3 but do not bind recombinant BAFF, indicating endogenous BAFF binding.

Conclusions:

• BAFF and APRIL are dispensable for B cell development in the bone marrow but crucial for B cell development in GALT.
• Endogenous BAFF produced by B cells may act in an autocrine fashion to maintain peripheral B cells.
• This autocrine BAFF signaling could be vital for sustaining peripheral B cell populations in adults after bone marrow lymphopoiesis ceases.