There are multiple definitions:

1. intraepithelial lymphocyte(English)

   • a unique cell population embedded within the intestinal epithelial layer, contributing to the formation of the mucosal epithelial barrier and serving as a first-line defense against microbial invasion. Mostly CD8+ T cells
   • LPL, IELp
   • Immunology
   • https://doi.org…1894-010-0148-6

2. internal elastic lamina(English)

   • fenestrated sheet that separates the arterial intima from the media, and affects macromolecular transport across the medial layer; separates EC from SMC
   • EEL, EC, SMC
   • Anatomy, Histochemistry
   • https://doi.org…80.2008.01020.x