The layered development of mouse B and T Cells

Area of Science:

• Immunology
• Developmental Biology
• Hematopoiesis

Background:

• Traditional lymphopoiesis models depict linear B and T cell development from fetus to adult.
• Emerging evidence suggests distinct lymphocyte populations arise during fetal development.
• Specific innate-like lymphocytes, such as Vγ3 γδ T cells and B-1 B cells, are preferentially generated prenatally.

Purpose of the Study:

• To review and synthesize data on distinct waves of lymphocyte development.
• To emphasize the role of hematopoietic stem cell-independent and -dependent development.
• To explore the implications of layered lymphocyte development for adult immunity and leukemia.

Main Methods:

• Synthesis of data from multiple laboratories.
• Emphasis on studies using mouse models.
• Analysis of differential regulation of innate and conventional lymphocyte emergence.

Main Results:

• Lymphocyte development occurs in distinct, differentially regulated waves.
• Innate and conventional B and T cells emerge through both hematopoietic stem cell-independent (fetal) and -dependent (adult) pathways.
• Fetal development preferentially generates specific innate-like lymphocytes.

Conclusions:

• Lymphocyte generation is layered, not strictly linear.
• Understanding these distinct developmental waves is crucial for comprehending adult immune system composition.
• This layered model offers insights into the origins of lymphocytic leukemias.