Decreased IL7Rα and TdT expression underlie the skewed immunoglobulin repertoire of human B-cell precursors from fetal origin.

Newborns are unable to mount antibody responses towards certain antigens. This has been related to the restricted repertoire of immunoglobulin (Ig) genes of their B cells. The mechanisms underlying the restricted fetal Ig gene repertoire are currently unresolved.

The Human Thymus Is Enriched for Autoreactive B Cells.

The human thymus has been shown to host B cells, which have been implicated in presentation of autoantigens for negative selection of T cell progenitors. Although these Ags are thought to be taken up through their surface Igs, data on thymic Ig gene repertoires are limited and reactivity to autoantigens has not been demonstrated. We therefore studied the Ig gene repertoires and reactivity to autoantigens of single-sorted B cells from pediatric thymus, and compared these with mature B cells from fetal and pediatric bone marrow.