Effects of granulocyte colony-stimulating factor on central and peripheral lymphocyte subset reconstitution after sublethal irradiation in mice / 中华放射医学与防护杂志

ABSTRACT

Objective To investigate the effects of recombinant human granulocyte colonystimulating factor(G-CSF) on central and peripheral lymphocyte subset reconstitution after a sublethal dose of irradiation. Methods Sixty female BALB/c mice were given a 6.0 Gy γ-ray total body irradiation (TBI) and randomly divided into 2 equal groups. The mice in G-CSF + TBI group were injected subcutaneously with recombinant human G-CSF 100 μg·kg-1·d-1 for 14 d and the mice in TBI group were injected subcutaneously with the same volume of phosphate buffered solution (PBS) once daily for 14 d. 7,14,21, and 28 d later the mice were killed and their thymus were taken out to prepare of the mononuclear cell suspension to analysis the percentage of thymic CD4 + CD8 + double positive, CD4 +CD8 - single positive, CD4 - CD8 + single positive and CD4 - CD8 - double negtive cells by flow cytometry. Peripheral blood samples were collected from the caudal vein twice a week, and the white blood cell(WBC) counts and absolute number of lymphocytes were assessed by automatic hemocyte analyzer. 14,28, and 60 d later blood samples were collected from angular vein to examine the peripheral lymphocyte subsets by flow cytometry. Cell counting kit-8 was used to detect lipopolysaccharide (LPS) or concanavalin A (ConA) stimulated splenic lymphocyte proliferation. Results The percentage of thymic CD4 + CD8 +double positive cells decreased 7 d after irradiation, rebounded at 14 d, decreased again at 21 d, and then got a permanent recovery. 28 d after irradiation the percentage of thymic CD4 + CD8 + double positive cells in the G-CSF + TBI group recovered to normal and was significantly higher than that of the TBI group (t =12. 22, P < 0. 05). 21d after irradiation the percentage of thymic CD4-CD8 + single positive cells of the G-CSF + TBI group was significantly higher than that of the TBI group (t = 3.77, P < 0. 05). The peripheral WBCs and lymphocytes decreased to the lowest levels 7 d after irradiation and then gradually increased, however, WBCs and lymphoeytes of the G-CSF + TBI group began to recover earlier and faster than the TBI group. The proportion of CD3 + CD8 + T cells of the G-CSF + TBI group was significantly higher than that of the TBI group 14 and 60 d after irradiation (t =4. 31,5.78, P <0.05). But there was no significant difference in the proportion of CD3 + CD4 + T cells between the two groups. The proportion of B lymphoeytes of the G-CSF + TBI group was significantly lower than that of the TBI group 14 d after irradiation(t =7.30, P <0.05), but it recovered quickly, and there were no significant differences in the proportion of B lymphoeytes between the two groups 28 and 60 d after irradiation. The proliferation indexes of splenic lymphocytes in response to LPS and ConA in the G-CSF + TBI group were 4. 37 and 2.98 times higher than those in the TBI group 14 d after irradiation. Conclusions G-CSF could accelerate the recovery of central and peripheral lymphocyte subsets, raise the absolute number of lymphocytes, and enhance their proliferative function, which contributes to the central and peripheral immune reconstitution after acute irradiation.