Consider two receptors, one inhibitory and one activating, on the surface of natural killer (NK) cells: KIR receptors that interact with certain class I MHC proteins, and special Fc receptors that recognize the tail region of IgG antibodies. When NK cells are incubated with an immortalized B cell line derived by infection of human B cells with Epstein-Barr Virus, the B cells are killed by NK cells. Normal B cells, in contrast, are not efficiently killed by NK cells. In each of the following scenarios, indicate whether the described changes are expected to enhance (E) or suppress (S) the cytotoxicity (killing activity) of the NK cells in this system. Your answer would be a four-letter string composed of letters E and S only, e.g. SEEE.
( ) The cell line is transformed with human class I MHC genes, and the genes are expressed.
( ) An anti-CD23 IgG antibody is added to the cells. (CD23 is a known marker on the surface of the immortalized B cells.)
( ) The cells are treated with stibogluconate, an inhibitor of KIR receptor signaling.
( ) Type I interferons are added to the cells.