OBJECTIVETo investigate the effects of interleukin 7 (IL-7) on B7 molecules expression and immunogenicity of acute leukemia (AL) cells.

METHODSThe B7 molecules expression on fresh acute leukemia cells and on the IL-7 exposed leukemia cells was detected by FACScan cytometer. B7-1 and B7-2 mRNA in IL-7 treated HL-60 cells were detected by reverse transcription-PCR (RT-PCR). The stimulation of proliferation of allogeneic peripheral blood mononuclear cells (PBMNC) by IL-7 treated leukemia cells was detected by MTT method. The level of interferon-gamma (IFN-gamma) secreted by the stimulated PBMNC was determined using enzyme-linked immunosorbent assays (ELISA). The blocking experiments were performed using monoclonal antibodies against B7-1, B7-2 and W6/32.

RESULTSB7-1 was weakly expressed in three, whereas B7-2 did in only one of eleven AL patients. IL-7 significantly enhanced B7 molecules expression on AL cells in a time-dependent manner. Furthermore, IL-7 could induce higher expression of B7-1 and B7-2 mRNAs on HL-60 cells. IL-7 treated leukemia cells could stimulate PBMNC proliferation and promote their IFN-gamma production. Anti-B7-1 and anti W6/32 but not anti-B7-2 monoclonal antibodies significantly inhibited the stimulated PBMNC proliferation and IFN-gamma secretion.

CONCLUSIONFresh AL cells express low level of B7-1 and B7-2 molecules. IL-7 enhances the B7 molecules expression on AL cells. The IL-7-treated leukemia cells can significantly stimulate the proliferation of allogeneic PBMNC and induce their IFN gamma secretion.