In Vitro Cellular Evaluation of Biosynergetic Effect of IL-15R

Objective To evaluate the biosynergetic effect of IL-15 receptor α subunit (IL-15R α) on cellular level. Methods IL-15 sensitive CTLL-2 cells were selected as target cells and MTT assay was adopted to determine the cell proliferation. After the dose-dependent relationship between the cell proliferation ratios and the IL-15 con-centrations being determined,moderate and lower levels of IL-15 were selected and paired with series double diluted IL-15R α in the process of CTLL-2 cells proliferation assay.In addition,cell proliferation in the presence of sole IL-15R α anti-IL-15 antibody or anti-IL-15R α antibody was also determined.Results Significant dose-dependent relationship exists between CTLL-2 cells proliferation and the IL-15 concentrations. The moderate and lower levels of IL-15 to stimulate the target cells proliferation were 50ng/mL and 10ng/mL respectively.As 50ng/ mL IL-15 was paired with 1ng/mL IL-15R α,the cells proliferation was increased significantly (0.270±0.008 vs. 0.593±0.026,P0.05),while 50ng/mL IL-15 paired,nearly 100-fold proliferation of targeted cells was observed (0.005±0.017vs.0.498±0.060,P0.05). Under the moderate and lower levels of IL-15,the concentrations of IL-15R α to reach the highest biosynergetic effect were 15.63ng/mL and 7.81ng/mL respectively. No proliferation was observed when sole IL-15R α added and the co-stimulation effect was significantly inhibited by anti-IL-15 antibody or anti-IL-15R α antibody.Conclusions The biosynergetic effect of IL-15R α is specifically mediated by IL-15 and more functional at lower IL-15 level. Suitable pairing ratio between IL-15 and IL-15R α is essential for the biosynergetic effect to achieve the highest level.