IL-7 potently restores both recall and primary responses to HY-disparate skin grafts in T-cell–depleted hosts receiving suboptimal T cell inocula.
(A) TXY/TCD mice were grafted with male tail skin and injected with 1 × 106 primed LN cells via tail vein 24 hours after grafting. Then rhIL-7 was injected intraperitoneally at a dose of 5 μg/d beginning on the day of primed cell injection and continuing for 28 days. Animals receiving rhIL-7 and 1 × 106 primed LN cells, shown in previous experiments to be a suboptimal inocula (▪, n = 8), rapidly rejected HY-disparate skin grafts at nearly the same rate as thymus-bearing animals (▴, dashed line, n = 9,P = .2) and significantly faster than animals injected with vehicle only plus primed LN cells (●, n = 9,P = .0002) or rhIL-7 without primed LN cells (♦, n = 6, P = .019). Note the lack of effect in thymus-bearing animals injected with rhIL-7 (▾, dashed line, n = 5) compared to vehicle (▴, dashed line, n = 5). (B) TXY/TCD mice were injected with 1 × 106 naive LN cells and enriched male dendritic cells. The rhIL-7 at 5 μg/d intraperitoneally was initiated on the day of cell injection and continued for 28 days. Male skin grafting was performed on day 21. Similar to recall responses, administration of rhIL-7 in the primary model led to rapid rejection of HY-disparate skin grafts in TCD mice (●, n = 8), whereas mice receiving the same inocula and injected with vehicle were completely unable to reject these grafts (▪, n = 7,P = .0002). Again, there was no difference between thymus-bearing mice injected with rhIL-7 (▴, dashed line, n = 6) or vehicle (♦, dashed line, n = 6).
