Fig. 6: Schematic illustration of the mechanisms that tumor-derived Igs strengthened tumor immune escape.

A Tumor-derived IgG neutralized B-cell-derived IgG to block CDC in which the formation of a complex, including B-cell-derived IgG, tumor antigen, and C1q, activated complement cascade to lysis tumor cells with the help of membrane attack complex in breast cancer cells. Finally, breast cancer cells escaped from the host immune system. B Tumor-derived IgG inhibited the proliferation of CD4⁺ or CD8⁺ T cells from CBMC and CBL to facilitate ovarian cancer immune escape. C The sialylation modification mediated the binding between tumor-derived IgG, which was recognized by RP215, and Siglecs on effector CD4⁺ and CD8⁺ T cells, which finally resulted in tumor immune escape due to the immunosuppressive effect of the above T cells and the promotion of tumor cell growth.