Transcriptome analysis identifies CCR7 and cell adhesion molecules as mediators of B cell migration to the bursa of Fabricius during chicken embryonic development.

The development of functional B lymphocytes during chicken embryogenesis relies on a series of tightly regulated processes. Precursor B cells migrate from the spleen via the blood to the bursa of Fabricius, where they colonize the bursal follicles to undergo further maturation and differentiation. To better understand the molecular mechanisms underlying early B cell migration in the chicken embryo, transcriptome analysis of B cells isolated from the spleen, blood, and bursa at embryonic days (ED) 12, ED14, and ED16 was performed. These findings suggest that sphingosine-1-phosphate (S1P) and its receptors regulate B cell presence in the bloodstream, while CCR7 and CXCR4 guide B cells to the bursa. Additionally, integrins and cell adhesion molecules, such as PECAM1, appear to facilitate transendothelial migration into the bursal mesenchyme. This study highlights a coordinated interplay between chemokines, integrins and cell adhesion molecules involved in B cell recruitment and colonization of the bursa microenvironment. These findings enhance our understanding of early B cell migration and shed light on the mechanisms governing B cell trafficking during chicken embryonic development.