Fig. 4. AQP4-IgG conjugated with toxin as a potential glioblastoma therapy: when AQP4-IgG binds to AQP4 located on astrocyte foot processes, the antibody-toxin complex remains on the cell surface without being internalized. In this case, the toxin remains linked to AQP4-IgG, preventing any cytotoxic effects on the astrocyte. Conversely, when AQP4-IgG binds to AQP4 expressed on glioblastoma cells, the complex is internalized into the tumor cell. Upon internalization, the toxin is released from the AQP4-IgG complex, inducing cytotoxicity and leading to the targeted destruction of the glioblastoma cell.