LAUSR

Lymphocytes B-1 cells are a subset of self-reactive B cells that arise in early life. Precisely how and why the immune system permits the development of self-reactive B cells in neonates remains a mystery. By studying B cell development in neonatal mice, Vanhee et al. uncovered the importance of RNA binding protein Lin28b in facilitating positive selection of self-reactive B-1 cells in neonates. They also found that ectopic expression of Lin28b was sufficient to promote selection of self-reactive B-1 cells in adult mice. The authors propose that Lin28b functions as a cell-intrinsic switch that jumpstarts the generation of B cells in early life. Sci. Immunol. 4 , eaax4453 (2019).