Fig. 1

Schematic description of MLR assay: PBMC and MSC co-culture, analysis, interpretation, and CTV-PBMC bank validation. a A pool of PBMC from 10 donors was labeled with CTV, frozen, and stored in liquid nitrogen in 100 vials. During 7 days, BM-MSC and CTV-PBMC were co-cultured at different ratios (BM-MSC/CTV-PBMC): 1/1, 1/3, 1/5, 1/10, 1/30, 1/100, and 1/300. b After culture, CTV-PBMC were collected and analyzed by flow cytometry to determine lymphocytes’ PD. The AUC of a linear section of the PBMC/MSC ratio-dependent PI of the lymphocyte proliferation curve was calculated. c A comparison between two CTV-PBMC banks was proceeded using BM-MSC from four donors. AUCs of the selected ratios of the two banks were non-statistically different (p value > 0.9999; two-tailed Wilcoxon matched-pairs signed-rank test; n = 4) and correlated (p value = 0.0417; two-tailed Pearson’s correlation test). Equation is [Bank 2] = 1.208 × [bank 1] – 0.01958 with a regression coefficient: R squared = 0.9188. d The-PBMC bank’s stability was tested for 509 days without a decrease in the lymphocytes’ PD or CD45+ cell viability after culture. The slopes of the curves representing either the PD or CD45+ viability over time are not significantly different from zero (Fisher test, p value = 0.9575 and 0.9355, respectively). The regression coefficient for these curves obtained is R squared = 9.033E−5 and 0.0284, respectively