Abstract: Objective To prepare monoclonal antibodies against human 4-1BBL molecule and analyze their biological characteristics. Methods The BALB/c mice were immunized with the cell line L929/4-1 BBL. The splenocytes from the immunized mice were fused with SP2/0, and then the hybridoma cells were screened with immunostaing and FACS. The isotype of the monoclonal antibody was identified by rapid isotyping analysis, and the 4-1 BBL expression profile on tumor cell lines was analyzed by indirect immunofluorescence with obtained mAb 39A8. Furthermore, the myeloid leukemia cell line U937 cells were stimulated with mAb 39A8 and their proliferation was measured with cell number counting. Results A hybridoma cell line named 39A8 was obtained, which had the property of secreting anti-human 4-1 BBL monoclonal antibody continuously and stably. The mAb 39A8 could recognize 4-1 BBL molecules on different cell lines and could enhance the proliferation of U937 cells in dose-dependent manner. Conclusion This work established an agonistic anti-human 4-1BBL mAb which may provide a useful tool for studying 4-1 BBL and its biological function.

Key words: 4-1 BBL, Hybriboma, Monoclonal antibody