Vol. 216, No. 5, May 6, 2019. 10.1084/jem.20181522.

The authors regret that in the original version of their paper, Laura Santambrogio and Mary Sue Brady were inadvertently omitted from the author list. The corrected author list appears above.

All versions of this article have been corrected.

This article is available under a Creative Commons License (Attribution 4.0 International, as described at https://creativecommons.org/licenses/by/4.0/).