Ontogeny, distribution and function of CD38-expressing B lymphocytes in mice

Area of Science:

• Immunology
• Cell Biology

Background:

• CD38 is a cell surface marker expressed on various immune cells, including B lymphocytes.
• The role of CD38 in B cell development and function is not fully understood, particularly in neonatal stages.

Purpose of the Study:

• To analyze the expression of CD38 on B lymphocytes during development and in different lymphoid compartments.
• To investigate the functional response of B cells to anti-CD38 stimulation at various developmental stages and in different B cell subsets.

Main Methods:

• Flow cytometry was used to analyze the expression of CD38, CD45R (B220), IgM, and IgD on splenic B lymphocytes from mice of different ages.
• B cell proliferation assays were performed using anti-CD38, anti-IgM, lipopolysaccharide (LPS), and anti-CD40 stimulation in the presence of IL-4.

Main Results:

• CD38 is expressed on both immature and mature B lymphocytes, as well as on progenitor B cells in the bone marrow.
• Neonatal B cells, despite expressing CD38 and IgM, failed to proliferate in response to anti-CD38 or anti-IgM cross-linking with IL-4, but responded to LPS and anti-CD40.
• B cell responsiveness to anti-CD38 and anti-IgM developed by 2 weeks of age, reaching adult levels by 4 weeks. Peritoneal B1 lymphocytes expressed high levels of CD38 and were unresponsive to anti-CD38 but responsive to LPS and anti-CD40.

Conclusions:

• CD38 expression is an early event in B cell development, present from progenitor stages through maturation.
• Neonatal B cells exhibit a developmental delay in acquiring responsiveness to anti-CD38 and anti-IgM stimulation, indicating functional immaturity.
• Peritoneal B1 lymphocytes, while expressing high CD38, display distinct activation pathways, relying on LPS and anti-CD40 rather than anti-CD38.