To explore the immunosuppressive ability of human umbilical cord mesenchymal stem cells (hUCMSCs) on T and B lymphocytes before and after cryopreservation and provide future for using the clinical application of hUCMSCs.

Human peripheral blood mononuclear cells were isolated from healthy human peripheral blood. Anti-CD3 and anti-CD8 monoclonal antibodies were used to activate T lymphocytes in vitro. Selected B lymphocytes were stimulated by ODN2395, human CD40 ligand, goat anti-human IgM antibodies and interleukin 2 in vitro. The cells were co-cultured with activated T and B lymphocytes, divided into a single stimulation group and hUCMSCs co-culture group (before and after cryopreservation) . The immunosuppressive ability of hUCMSCs on activated T and B lymphocytes were analyzed. In addition, the differences immunosuppressive ability of hUCMSCs before and after cryopreservation were also studied. The differences between groups were compared by t-test, and the differences among groups were compared by repeated measures design analysis of variance.

Compared with hUCMSCs before cypropreservation, the proliferation of CD3⁺T cells (37.60﹪±0.54﹪vs 39.40﹪±1.57﹪) , CD4⁺T cells (36.87﹪±0.54﹪vs 38.63﹪±1.39﹪) and CD8⁺T cells (40.37﹪±1.14﹪vs 42.47﹪±1.90﹪) (P > 0.05) were not significantly inhibited after cryopreservation. The apoptosis of CD3⁺T cells (18.07﹪±0.66﹪vs 16.77﹪±1.15﹪) , CD4⁺T cells (26.47﹪±1.13﹪vs 24.60﹪±1.47﹪) and CD8⁺T cells (3.52﹪±0.22﹪vs 2.72﹪±0.06﹪) had no significant difference (P > 0.05) . The proportion of regulatory cells (Treg) subsets (5.51﹪±0.71﹪vs 6.87﹪± 0.27﹪) had also no significant difference (P > 0.05) . hUCMSCs did not reduce the proportion of helper T cell (Th) subsets, especially the proportion of Th1 subsets (0.47﹪± 0.09﹪vs 0.33﹪± 0.04﹪) and Th17 subsets (0.21﹪± 0.04﹪vs 0.22﹪± 0.03﹪) (P > 0.05) . For B lymphocytes, hUCMSCs reduced the proportion of Th2 cell subsets (0.73﹪±0.07﹪vs 0.49﹪±0.06﹪) and IgM antibody secretion [ (739.70±28.39) ng/mL vs (560.21±3.81) ng/mL] after cryopreservation (P < 0.05) . There was no significant difference in proliferation and apoptosis of B lymphocytes, and reduced secretion of IgA and IgG antibodies before and after hUCMSCs cytopreservation (P > 0.05) .

After cryopreservation, hUCMSCs were more powerful than those before cryopreservation in reducing the proportion of Th2 cell subsets and the secretion of IgM antibodies. However, the immunosuppressive abilities was same. Both hUCMSCs before and after cryopreservation have high clinical application value.