FRC-derived retinoic acid: The key to unlocking milky spots.

Milky spots of the omentum enable lymphocyte access to the peritoneal cavity. In this issue of JEM, Yoshihara and Okabe (2023. J. Exp. Med.https://doi.org/10.1084/jem.20221813) demonstrate how secretion of retinoic acid by fibroblastic reticular cells allows lymphocyte entry into milky spots and the peritoneal cavity.