Novel Peptides Capable of Altering NK Cell Activity

Peptides capable of binding to HLA-E and affecting immune cell activity are provided. Such peptides can selectively activate NKG2C+ immune cells such as natural killer (NK) cells and/or can inhibit NKG2A+ cells to decrease or suppress immune cell responses. Methods of use of the peptides are also disclosed, for instance, for treating or inhibiting the development or progression of a multitude of illnesses and conditions, including autoimmune disease, infectious disease such as viral or bacterial infection, and proliferative disorders such as cancer.