Human/mouse chimeric anti-CD20 monoclonal antibody enhances antigen presentation in dendritic cells and induces anti-lymphoma CTL effects / 中国实验血液学杂志

ABSTRACT

In order to investigate the cellular immunoresponses mediated by chimeric anti-CD20 monoclonal antibody (anti-CD20 McAb) through dendritic cells (DCs), mononuclear cells were isolated from human peripheral blood (PBMNC) and DCs from PBMNCs in vitro were generated with normal methods. Human CD20 positive lymphoma cell line-Raji cells were treated with different methods including treatment with anti-CD20 McAb (group R), treatment with heat-induced apoptosis (group A) and treatment with anti-CD20 McAb+heat-induced apoptosis (group R+A), then Raji cells treated with above-mentioned methods as tumor antigen were loaded on DCs. The phagocytosis of DCs to tumor antigen was observed by transmission electron microscope (TEM), the auto-mixed lymphocyte reaction was performed with antigen-primed DCs, the release of INF-gammafrom effector cells was detected by ELISPOT, the killing of effector cells on Raji cells was assayed by MTT. The results showed that under TEM, no pronounced phagocytosis of DCs was seen in group R, while the phagocytosis of apoptotic bodies could be easily seen in group A and the more cell fraqments were observed in group R+A. The FCM indicated that the expressions of CD80, CD86 and HLA-DR on DCs in 3 experimental groups were higher than those in group control (p<0.05), while expression positive rate in group R+A was higher than those in group R and A (p<0.05). The detection of lymphocyte surface antigen revealed that proportions of CD8+ cells in all experimental groups were higher than those in group control (p<0.05), count of CD56+ cells in group R and R+A increased, as compared with group A and control, difference was significant (p<0.05). ELISPOT assay indicated that amount of cells releasing IFN-gamma in all experimental groups was higher than that in group control, and also number of spots in group R+A significantly higher than that in other groups at effector-targetor ratio=110 (p<0.05). The results of killing assay demonstrated that killing rate on Raji cells in all experimental groups increased as compared with group control (p<0.05), while killing rate in group R+A was higher than that in group R and A. It is concluded that anti-CD20 McAb can mediate DC to induce cellular immunoresponse against lymphoma, that is, to stimulate and amplify specific CTLs and NK cells. Anti-CD20 McAb combined with DCs primed by heat-stressed tumor cells as antigen can further enhance cellular immunoresponse against lymphoma.