OBJECTIVETo study the ex vivo effect of sirolimus on capacity of splenic dendritic cells (DC) from traumatized mice in inducing T cell responses.

METHODSTwenty-four BALB/c mice were divided into control group and trauma group according to the random number table, with 12 mice in each group. Mice in trauma group were bled followed by closed femur fracture after anaesthesia, while mice in control group were only anaesthetized without injury. Twenty-four hours later DC were isolated from spleens and divided into 4 subgroups: sirolimus devoid control (trauma) groups [consisted of cells from control (trauma) groups, without sirolimus treatment] and sirolimus treated control (trauma) groups [consisted of cells from control (trauma) groups, treated with 10 microg/L sirolimus for 6 hours]. Then their autophagic activity, DC-induced mixed lymphocyte reaction (MLR) were measured and recorded as fluorescence intensity (FI) value and absorbance value respectively. The expression of major histocompatibility complex class (MHC) II and costimulatory molecules CD40, CD80, and CD86 on DC surface were measured with flow cytometry. IL-12p40, IL-12p70 and IL-10 levels in lipopolysaccharide-stimulated DC supernatants were determined by ELISA. Data were processed with one-way analysis of variance.

RESULTS(1) Compared with those of sirolimus devoid control group (FI value = 22 +/- 6), DC autophagic activity (FI value = 13 +/- 2) and DC-induced MLR in mice from sirolimus devoid trauma group were significantly weakened (F = 212.836, P < 0.05). Compared with those of sirolimus devoid control (trauma) groups, DC autophagic activity in mice from sirolimus treated control (trauma) groups (FI = 45 +/- 8, 44 +/- 8 respectively) were significantly strengthened (F = 212.836, P < 0.05 or P < 0.01). MLR in mice from sirolimus treated trauma group was stronger than that from sirolimus devoid trauma group (with F value respectively 101.426, 86.533, P values all below 0.05). (2) Compared with those of sirolimus devoid control group [MHC II (85 +/- 6)%, CD40 (8 +/- 1)%], the expressions of MHCII [(60 +/- 9)%] and CD40 [(4 +/- 1)%] on DC surface from sirolimus devoid trauma group were significantly reduced (with F value respectively 37.918, 40.426, P values all below 0.05). The expression of MHCII from sirolimus treated trauma group [(78 +/- 7)%] was higher than that from sirolimus devoid trauma group (F = 37.918, P < 0.05). (3) IL-12p40, IL-12p70 secretion by DC from sirolimus devoid trauma group [(120 +/- 13), (10 +/- 3) pg/mL] were significantly reduced as compared with those from sirolimus devoid control group [(200 +/- 25), (20 +/- 6) pg/mL, with F value respectively 218.646, 310.253, P values all below 0.05]. Compared with those from sirolimus devoid control (trauma) groups, IL-12p40 [(560 +/- 34), (540 +/- 29) pg/mL], IL-12p70 [(55 +/- 8), (60 +/- 11) pg/mL] secretion by DC from sirolimus treated control (trauma) groups were obviously enhanced (with F value respectively 218.646, 310.253, P values all below 0.01), while IL-10 secretion levels were significantly decreased (F = 246.108, P < 0.01).

CONCLUSIONSSirolimus can partially ameliorate DC functions ex vivo in traumatized mice, and further enhance the capacity of DC in inducing T cell responses.