The present invention provides a fusion protein comprising an IL-2 protein and a CD80 protein. A fusion protein comprising a CD80 fragment, an immunoglobulin Fc, and an IL-2 variant, in one embodiment, can activate immune cells, such as natural killer cells, and, at the same time, can control the immune cell regulatory activity of regulatory T cells. Therefore, a pharmaceutical composition comprising the fusion protein as an active ingredient can increase the immune activity in vivo and can be effectively used for not only cancer but also infectious diseases, and thus is highly industrially applicable.
