OBJECTIVETo analyze in vitro the effect of mesenchymal stem cells (MSCs) on secreting cytokines by T lymphocytes and ratio of CD4⁺CD25⁺ T cells from patients with immune thrombocytopenia (ITP).

METHODSHuman bone marrow-derived MSCs were isolated by Ficoll Hypaque and cultured for proliferating to passage cells. Allogeneic T lymphocytes of health adults and ITP patients were isolated from peripheral blood by Ficoll Hypaque and nylon cotton column, and the ratio of CD4⁺CD25⁺ T cells was detected by flow cytometry. Then the different amounts of 1 × 10⁴, 5 × 10⁴, 2 × 10⁵ MSCs per well treated with mitomycin as stromal feeder layers were co-cultured with above-mentioned T lymphocytes, 5 days after cocultivation, the ratio of CD4⁺CD25⁺ T cells was detected by flow cytometry and the levels of IL-2, IFN-γ, IL-4, IL-10 were measured by enzyme- linked immune sorbent assay (ELISA).

RESULTSAfter co-cultured with 2 × 10⁵ MSCs for 5 days, the ratio of CD4⁺CD25⁺ T cells and CD4⁺CD25⁺/CD4⁺ were significantly higher than of separate T lymphocytes in ITP patients [(4.56 ± 0.70)% vs (2.24 ± 0.81)%, (9.91 ± 1.18)% vs (4.08 ± 1.17)%, respectively] (P<0.05). To compare with separate T lymphocytes in ITP patients, the cytokine concentrations of IL-2 and IFN-γ from the culture supernatants significantly reduced from (280.47 ± 17.33) pg/ml to (97.21 ± 12.07) pg/ml and from (129.33 ± 16.34) pg/ml to (72.75 ± 7.81) pg/ml, respectively. In contrast, the cytokine concentrations of IL-4 and IL-10 increased from (16.34 ± 2.60) pg/ml to (37.98 ± 4.05) pg/ml and from (54.78 ± 5.62) pg/ml to (113.77 ± 5.68) pg/ml, respectively.

CONCLUSIONMSCs significantly inhibited the cytokine levels of IL-2 and IFN-γ secreted by Th1 cells and promoted the releases of IL-4 and IL-10 by Th2 cells in ITP , thereby regulating the balance between Th1 and Th2 reaction, as well as up-regulating the expression of CD4⁺CD25⁺ T cells in vitro,then induced the immunologic tolerance of ITP.