Antileukemic effects in vitro of new co-stimulatory molecule CD137 / 中国实验血液学杂志

ABSTRACT

This study was aimed to investigate the expression characteristics of new co-stimulatory molecule CD137 (4-1BB) on human T lymphocytes and antileukemic effects of monoclonal antibody hCD137mAb in stimulating the T lymphocyte proliferation, promoting the cytokine secretion, enhancing the cell killing effect and so on. The expression of CD137 on normal T lymphocytes treated with phytohemagglutinin (PHA) was detected by FACS and indirect immunofluorescence. In HL-60 and T lymphocyte system in vitro, the effect of hCD137mAb and PHA on T lymphocyte proliferation was tested by MTT colorimetric assay. The IFN-gamma and IL-4 expression levels on the surface of T cells were detected by FACS and indirect immunofluorescence. In vitro mixed lymphocyte tumor cell culture (MLTC) system, the function of hCD137mAb enhancing toxicity killing leukemic cells at different effect-target ratio were studied. The results showed that almost no expression of hCD137 was found in T cells without PHA stimulation, but after activation of T cells by PHA, the expression gradually increased with a peak at 7th day (FACS 56.4%+/-1.98%, indirect immunofluorescence 52.8%+/-2.01%). CD137mAb alone could not stimulate T cell proliferation (proliferation index 1.002+/-0.011), but could enhance PHA stimulating activity (proliferative index of 2.161+/-0.102) about 2-folds (proliferation index 4.705+/-0.133). Moreover, hCD137mAb increased expression of IFN-gamma high by about 3-fold in presence of PHA, but did not effect on IL-4. The hCD137mAb markedly enhanced T cell killing activity on HL-60 cell line and its co-stimulatory effect was best at the effect-target ratio of 401 with increasing of killing percentage by about 2-fold. It is concluded that the new co-stimulatory molecule CD137 has significant antileukemic effect, use of hCD137mAb is an effective, safe and simple immunization strategy for leukemia therapy, this study provides some experimental basis for clinical immunotherapy with CD137 mAb.