FL B cells promote a prolonged CCL2 production by HD-MSCs. (A) HD-MSCs were stimulated for 3 days by TNF/LT (n = 3) or were cocultured with RL (n = 5), VAL (n = 5), or BL2 (n = 4) B-cell lines, or with purified primary FL B cells (n = 13). Three FL B cells were cocultured with 2 different HD-MSCs (green triangles, blue squares, and red circles, respectively). CCL2 concentration was then measured in cell supernatants by ELISA, and the results are expressed as the fold change compared with untreated HD-MSCs. *P < .05; ***P < .001; ns indicates not significant. (B) HD-MSCs were cultured for 3 days with RL or VAL before cell sorting of CD19/CD20^posCD105^negDAPI^neg viable B cells and CD19/CD20^neg CD105^posDAPI^neg viable MSCs and quantification of CCL2 by RQ-PCR in each cell fraction. Same experiments were conducted with HD-MSCs, RLs, and VALs cultured alone. Each CCL2 Ct value was normalized to matched GAPDH Ct value. The results are the mean ± SD from 3 experiments. *P < .05; **P < .01. (C) HD-MSCs were cultured for 3 days with RL or VAL before collection of cell supernatant (day 0). HD-MSCs were then detached, depleted from residual B cells, and seeded again in culture for 10 days. CCL2 concentration was measured in day 0, day 4, and day 10 cell supernatants by ELISA. Results are expressed as the fold change compared with untreated HD-MSC. Shown is 1 representative from 2 independent experiments. (D) Migration of purified peripheral blood monocytes in response to supernatants from RLs, VALs, HD-MSCs, and HD-MSCs maintained during 3 days in coculture with RL or VAL. Monocyte migration index is calculated as the number of TOPRO-3^negCD14^pos viable monocytes migrating in response to cell supernatant divided by their number in response to migration medium. Results represent the mean ± SD from 5 independent experiments. *P < .05