Preformed CD40L is stored in Th1, Th2, Th17, and T follicular helper cells as well as CD4+ 8- thymocytes and invariant NKT cells but not in Treg cells.
Koguchi Y, Buenafe AC, Thauland TJ, Gardell JL, Bivins-Smith ER, Jacoby DB, Slifka MK, Parker DC. PLoS One. 2012; 7(2):e31296. Epub 2012 Feb 21.