Which immune cells can kill cancerous cells that lack MHC markers?

A) effector B cells only
B) cytotoxic T cells only
C) natural killer cells only
D) cytotoxic T cells and natural killer cells
E) cytotoxic T cells and effector B cells

Natural killer (NK) cells are capable of killing cells that lack MHC (Major Histocompatibility Complex) markers, including cancerous cells. Unlike cytotoxic T cells, which require the presence of specific antigens presented by MHC molecules to recognize and kill target cells, NK cells can recognize and eliminate cells that have downregulated MHC molecules, a common evasion strategy used by cancerous cells.