Interleukin (IL)-15R[alpha]-deficient natural killer cells survive in normal but not IL-15R[alpha]-deficient mice

Abstract

Natural killer (NK) cells protect hosts against viral pathogens and transformed cells. IL-15 is thought to play a critical role in NK cell development, but its role in the regulation of peripheral NK cells is less well defined. We now find that adoptive transfer of normal NK cells into mice lacking the high affinity interleukin (IL)-15 receptor, IL-15Ralpha, surprisingly results in the abrupt loss of these cells. Moreover, IL-15Ralpha-deficient NK cells can differentiate successfully in radiation bone marrow chimera bearing normal cells. Finally, adoptively transferred IL-15Ralpha-deficient NK cells survive in normal but not IL-15Ralpha-deficient mice. These findings demonstrate that NK cell-independent IL-15Ralpha expression is critical for maintaining peripheral NK cells, while IL-15Ralpha expression on NK cells is not required for this function.

Figure 1.

Adoptively transferred NK cells survive significantly longer in a WT host than in a KO host. (a) Representative FACS^® plot of transferred WT NK cells in WT (left) and KO (right) hosts. Splenic WT NK cells were transferred intravenously into either WT or KO hosts, congenic for the Ly5 marker. 2 d after transfer, peripheral blood from these mice were analyzed for presence of NK cells using antibodies against Ly5.1, Ly5.2, NK1.1, and CD3. Events displayed are gated on donor cells among the lymphoid gate and presented as the percentage of NK cells among donor cells for this and all subsequent figures. (b) Peripheral blood (PBL) analysis of adoptively transferred WT NK cells in WT (▪) or KO (□) mice at indicated times after transfer. Data presented is the percentage of transferred NK cells/total lymphoid cells collected for this and all subsequent NK cell transfer experiments. (c) Long term PBL analysis of adoptively transferred WT NK cells in WT (▪) or KO (□) mice. Data are representative of three experiments, with three mice in each experiments.

Figure 2.

The disappearance of adoptively transferred NK cells from peripheral blood is not due to differential homing to specific tissues. Quantitation of adoptively transferred WT NK cells from various tissues, (a) spleen, (b) LN, (c) PBL, (d) peritoneum, (e) liver, (f) lung of WT (left) or KO (right) mice 48 h after adoptive transfer. Events displayed in histogram represent percentage of transferred CD3⁻ NK1.1⁺ cells within the lymphoid gate. Data are representative of two experiments with two mice each.

Figure 3.

Adoptively transferred splenic NK cells do not proliferate in the absence of specific stimuli. (a) Proliferation of WT NK cells in response to PBS 4 d after transfer into WT host. Events displayed in histogram represent transferred CD3⁻ NK1.1⁺ cells obtained from the peritoneum of recipient mice. (b) Proliferation of WT NK cells in response to IL-15 4 d after transfer into WT host. (c) Proliferation of WT NK cells in response to IL-15 (5 μg/day) 4 d after transfer into KO host.

Figure 4.

WT and KO mice express similar amounts of IL-15 mRNA. Reverse transcriptase-PCR analysis of secreted and nonsecreted forms of IL-15 mRNA was performed on splenic RNA from mice treated with poly I:C for the indicated number of days.

Figure 5.

Long term survival of transferred WT NK cells in WT BM→KO radiation BM chimera ⋄ WT BM→WT, ▪ WT BM→KO, ♦ KO BM→KO. Radiation BM chimeric mice were prepared as described in Materials and Methods, allowed to recover for at least 8 wk, and were then used as recipients for WT splenic NK cells. Adoptively transferred cells were congenic for the radiation sensitive compartment of the chimeric mice. Data are representative of two experiments, with two mice each.

Figure 6.

KO NK cells can survive in the peripheral tissues of KO BM→WT chimera mice. Radiation BM chimeric mice were prepared as described in Materials and Methods and allowed to recover for at least 8 wk before analysis. (a) Representative FACS^® plot of BM-derived NK cells in spleens of KO BM→WT (top panel) versus KO BM→KO chimera (bottom panel). (b) Percentage of BM derived NK cells obtained from spleens and peripheral blood of KO BM→WT (▪) and KO BM→KO (□) chimera. Data are representative of five mice.

Figure 7.

IL-15Rα on NK cells is not required for their peripheral maintenance. Long term serial peripheral blood analysis of adoptively transferred KO NK cells after transfer into either WT (▪) or KO (□) hosts. Data are representative of two experiments, with two mice each.