The experimental study on biodistribution and radioimmunoimaging of 131I labeled anti-lymphoma Fab antibody in nude mice bearing human B cell lymphoma

Objective: Radioimmunoimaging is still an interesting study in the domain of nuclear medicine. The aim of this study was to evaluate the biodistribution and radioimmunoimaging of 131I-Fab anti- body in nude mice beating human B cell lymphoma. Methods: The immunoreactivity of Fab antibody to Raji cells was analyzed by immunohistochemistry and flow cytometry. Fab antibody and CD20 monoclonal antibody (as control) were labeled with 131I using Iodogen method. 131I-Fab antibody or 131I-CD20 was injected into nude mice bearing B cell lymphoma via tail veins. The biodistribution and radioimmunoimaging results were obtained at 2, 4, 8 and 24 h postinjection, respectively. Results: The results of immunohistochemistry and flow cytometry indicated that both Fab antibody and 131I-Fab antibody could bind strongly with membrane antigens on Raji cells, and the binding rate reached above 87%. Clear tumor image was obtained at 8 h after injection with 131I-Fab and elimination was observed at 24 h postinjection. The clear tumor image for 131I-CD20 antibody was obtained at 24 h post injection. The biodistribution in vivo showed that the percentage activities of injection dose per gram of tumor (% ID/g) of 131I-Fab group at 2, 4, 8 h postinjection were higher than that of 131I-CD20 antibody [(1.37±0.28), (1.84±0.13), (2.21±0.15)% ID/g vs (0.33±0.06), (0.62±0.08), (1.46±0.24)% ID/g, respectively; F=52.22, 278.42 and 29.00, all P<0.05], but lower at 24 h [(0.44±0.07)% ID/g vs (3.56±0.66)% ID/g; F=89.7, P<0.05]. The tumor/non-tumor (T/NT) ratios for 131I-Fad and 131I-CD20 groups at 2, 4, 8 and 24 h were [(0.22±0.03)-(5.44± 0.31)] vs[(0.04±0.01)-(3.10±0.29)], [(0.43±0.11) - (21.01±3.97)] vs [(0.11±0.05) - (7.99±1.81)], [(1.09±0.07) -(20.28±2.77)] vs [(0.48±0.06) - (23.55±1.69)], [(1.12± 0.02) - (10.29±1.78)] vs [(2.32 ± 0.34) - (33.23±6.83)], respectively. Conclusion: 131I-Fab anti- body has advantages of small molecular weight, excellent targeting characteristics, early imaging and fast elimination, which indicates the potential application value in diagnosing B cell lymphoma. (authors)