Mice Lacking IL-15 or the IL-15R $\alpha$ Chain Have Substantially Reduced Numbers of Type B IELs, Including

Mice lacking IL-15 or the IL-15R $\alpha$ chain have substantially reduced numbers of type b IELs, including both $\alpha$ : $\beta$ and $\gamma$ : $\delta$ T-cell receptor-positive subsets. Normal numbers of type b IELs can be restored in il15^-/- mice by cell-type specific expression of IL-15 in:

A) Thymic medullary epithelial cells
B) Thymic cortical epithelial cells
C) Dendritic cells
D) CD8 $\alpha$$\alpha$ ⁺ T cells
E) Intestinal epithelial cells