Lack of IL-7 signaling in APCs leads to a partial abrogation of the effect of IL-7 in restoring primary responses to HY skin grafts.

TXY/TCD mice were injected with naive LN cells and 1 × 10⁵ enriched dendritic cells from the spleens of male IL-7Rα^−/− mice or normal, IL-7Rα^+/+males. The rhIL-7 at 5 μg/d or vehicle was initiated on the day of cell injections and continued for 28 days. Male skin grafting was performed on day 21. IL-7Rα^−/− APCs are functionally able to induce HY graft rejection in animals receiving a sufficient T-cell inocula (25 × 10⁶) with vehicle (▪, n = 5) at a rate analogous to thymus-bearing animals receiving enriched IL-7Rα^+/+ dendritic cells (▾, n = 5). Mice receiving an insufficient LN inocula (1 × 10⁶) with vehicle are completely unable to reject these grafts (♦, n = 6). Mice injected with a suboptimal T-cell inocula, sensitized with IL-7R^−/− APCs and given rhIL-7 (●, n = 11) rejected HY-disparate skin grafts but significantly slower than mice receiving IL-7Rα^+/+ dendritic cells (▴, n = 10,P = .006).