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Human Naive and Memory T Cells Display Opposite Migratory Responses to Sphingosine-1 Phosphate
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International audience. The role of sphingosine-1 phosphate (S1P) in leukocyte trafficking has been well deciphered in mice but remains largely unaddressed in humans. In this study, we assessed the ex vivo response to S1P of primary human T cell subsets. We found that tonsil but not blood leukocytes were responsive to S1P gradients, suggesting that T cell responsiveness is regulated during their recirculation in vivo. Tonsil naive T cells were readily chemoattracted by S1P in an FTY720-sensitive, S1PR1-dependent manner. Surprisingly, S1P had the opposite effect on effector memory T cells, resident memory T cells, and recently activated T cells, inhibiting their spontaneous or chemokine-induced migration. This inhibition was also more pronounced for CD4 T cells than for CD8 T cell subsets, and was dependent on S1PR2, as shown using the S1PR2 antagonist JTE-013. S1PR1 was progressively downregulated during T cell differentiation whereas S1PR2 expression remained stable. Our results suggest that the ratio between S1PR1 and S1PR2 governs the migratory behavior of T cell subsets. They also challenge previous models of the role of S1P in lymphocyte recirculation and suggest that S1P promotes retention of memory T cell subsets in secondary lymphoid organs, via S1PR2.
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