OBJECTIVETo investigate the mechanisms of in vivo rhG-CSF affecting T lymphocyte.

METHODSPeripheral blood and apheresis graft were obtained from sibling donors before and after G-CSF administration. Proliferation of peripheral blood mononuclear cells (MNC) stimulated by PHA before and after removing monocyte by plastic-adherence was detected by MTT test. Absolute number of MNC, costimulating molecules expression on antigen presenting cells (monocyte and B lymphocyte) and the number of CD(14)(+) cells before and after plastic-adherence treatment were analyzed by flow cytometry.

RESULTSAfter rhG-CSF administration, absolute peripheral blood monocyte counts increased by 4.2 +/- 1.74 times. By removing monocytes, proliferation of T cells after rhG-CSF administration partly restored, but remained 20.58% lower than that before G-CSF treatment. CD(86) co-stimulating factor expression on monocyte declined (66.96 +/- 13.87)% and mean fluorescence intensity (MIF) decreased (31.31 +/- 12.91)% after rhG-CSF administration. Expression of CD(80) on B lymphocyte decreased (45.77 +/- 26.58)%.

CONCLUSIONSThe increased number of monocytes after rhG-CSF administration suppressed T-cell proliferation, which was partly the mechanism of the T-cell hyporesponsiveness. The fact that monocyte and B lymphocyte expressed low level of B(7) co-stimulating factor suggested that antigen present cells might also mediate the alteration of T-cell proliferation.