Why Vitamin D Is Essential (redOrbit) Image 1: T lymphoycte cell (small cell with red surface) scanning another cell for the presence of foreign molecules. Credit: Professor Carsten GeislerImage 2: When the naïve T cell recognizes foreign molecules with its T cell receptor (TCR) it sends activation signals (1) to the VDR gene. The VDR gene now starts the production of VDR (2). VDR binds vitamin D in the T cell (3) and becomes ... [News Source]