Sphingosine 1-phosphate receptor 1 promotes B cell localization in the splenic marginal zone

The factors directing marginal zone B cells to the splenic marginal zone are not well understood. Here we report that FTY720, a drug that targets sphingosine 1-phosphate (S1P) receptors, induced marginal zone B cell migration into follicles. Marginal zone B cells expressed S1P receptors 1 and 3 (S1P(1) and S1P(3), respectively). Using gene-targeted mice, we show that S1P(1) but not S1P(3) was required for localization in the marginal zone. In mice lacking the chemokine CXCL13, S1P(1)-deficient marginal zone B cells reacquired a marginal zone distribution. Exposure to lipopolysaccharide or antigen caused marginal zone B cells to downregulate S1P(1) and S1P 3 and to migrate into the splenic white pulp. These data suggest that marginal zone B cell localization to the marginal zone depends on responsiveness to the blood lysophospholipid S1P, with S1P(1) signaling overcoming the recruiting activity of CXCL13.