[The influence of mycophenolate mofetil upon the maturation and allostimulatory activity of cultured dendritic cell progenitors and the effects of tolerance induction in allograft recipients].

OBJECTIVE

To investigate the influence of mycophenolate mofetil (MMF) on the maturation and allostimulatory activity of cultured dendritic cell progenitors (DCPs) and to evaluate the efficacy of pretreatment of donor dendritic cells (DCs) with MMF in tolerance induction in allograft recipients and its possible mechanism.

METHODS

DCPs of Balb/c mice were cultured in culture fluid containing recombinant mouse granulocyte-macrophage colony stimulating factor (GM-CSF), and then divided into 4 groups: control group, MMF group, lipopolysaccharide (LPS) group, and MMF + LPS group. Seven days later, flow cytometry was used to analyze the phenotypes of the DCs. ELISA was used to examine the level of IL-12 in the supernatant. T cells from the spleens of C57/BL6 mice were cultured together with inactivated DCs from Balb/c mice, and added with [(3)H]-TdR. Mixed lymphocyte reaction (MLR) was analyzed. The DCs and MMF-DCs cultured for 5 days were co-cultured with T hybridoma cells of the line MF2.2D9 in culture fluid containing ovalbumin (OVA). Twenty-four hours later, the supernatant was collected and ELISA was used to measure the level of interleukin (IL)-12 so as to reflect the antigen-presenting ability of the DCs. OVA immunized C57/BL6 mice for 4 times. 21 days after T cells were collected from the spleens and co-incubated with DCs and MMF-DCs, [(3)H]-TdR was added and the values of counts per minute (cpm) were calculated so as to analyze the antigen-specific proliferation. Twenty-four Balb/c mice were randomly divided into 3 groups: group A (without treatment), group B (treatment with intravenous injection of untreated DCs of Balb/c mice), and group C (treatment with intravenous injection of DCs of Balb/c mice treated with MMF), and then transplanted with the hearts of C57/BL6 mice. The functions of the transplanted hearts were evaluated by touching the arterial pulse and histological examination. ELISA was used to detect the levels of Th1 cytokines, such as IL-12, IL-4, IL-10, IL-2, and IFN-gamma, in the cultured DCs and in the sera of the recipients 7 and 14 days after culture or transplantation.

RESULTS

The immunophenotypic analysis showed that in comparison with those in the control group and the LPS group the expressions of the costimulatory molecules, Ia(d), CD80, and CD86, of the DCPs were significantly weaker in the MMF-group and MMP + LPS group. The IL-12 levels in the supernatant of the MMF and MMF + LPS groups of DCPs were significantly lower than those in the other groups (P < 0.01). The IL-12 level of the MF2.2D9 cells treated with MMF-treated DCs was significantly lower than control group (P < 0.01). The ability to stimulate proliferation of T cells of the same genotype in the MMF-DC group was significantly inhibited (P < 0.01). The survival time of the transplanted heart was 30.50 +/- 3.25 days in the C57/BL6 mice injected with untreated DCPs of Balb/c mice (21.25 +/- 2.12, P < 0.01) and that in the control C57/BL6 mice (8.63 +/- 1.06 days, P < 0.01) and with a significant difference between the latter 2 groups too (P < 0.01). The levels of, such as IL-2 and IFN-gamma, 7 and 14 days after heart transplantation of the group B were all significantly lower than those of the group A (both P < 0.05). The IL-2 and IFN-gamma levels 7 days after the heart transplantation were similar to those in the group B (both P > 0.05) and even lower than those of the group C (both P < 0.05). The IL-10 level in the groups B and C were all higher than those in the group A (all P < 0.05) with a significant difference between the group B and group C. The level of IL-4 was not significantly different among the 3 groups.

CONCLUSION

MMF has a significant suppressive effect on the maturation and function of DCs, which leads to a donor-specific tolerance in transplant recipients.