Interleukin‐15 preferentially promotes the growth of intestinal intraepithelial lymphocytes bearing γδ T cell receptor in mice

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Abstract
Several cytokines including stem cell factor (SCF) and interleukin (IL)‐7 are known to be required for development of γδ T cell receptor (TCR) intestinal intraepithelial lymphocytes (i‐IEL) in mice. We show here the effects of IL‐15 on the proliferation and maintenance of murine γδ i‐IEL in vitro. γδ i‐IEL constitutively expressed a high level of IL‐15 receptor α mRNA and proliferated in response to IL‐15 more vigorously than αβ i‐IEL. Vγ/δ repertoire analysis revealed that IL‐15, like IL‐2, induced polyclonal expansion of γδ i‐IEL, whereas γδ i‐IEL responding to IL‐7 showed a Vγ/δ repertoire skewed towards Vγ1/Vδ4, Vδ5. IL‐15 efficiently prevented γδ i‐IEL from apoptosis induced by growth factor deprivation. This rescue was accompanied by up‐regulation of Bcl‐2 expression. These results suggest that IL‐15 plays important roles in proliferation and maintenance of γδ i‐IEL.