Klas Kärre (born January 12, 1954 in Strasbourg, France) is a Swedish immunologist.
Kärre received his doctorate in 1981 at Karolinska Institutet[1] and is a professor of molecular immunology at Karolinska Institutet since 1993.
In the mid-1980s Kärre discovered one of the mechanisms for how cells of the immune system, natural killer cells (NK cells), identify their target cells and kill them.[2] The findings were that the NK cells are inhibited by a transplantation antigen, the major histocompatibility complex (MHC) class I, which prevents NK cells from kill their target cells. When MHC class I is removed from the target cells, they are killed by the NK cells. Kärre named this phenomenon "the missing self hypothesis".
Kärre became a member of the Nobel Committee for Physiology or Medicine in 2006 and its chairman in 2009.[3] In 2009, he was elected a member of the Royal Swedish Academy of Sciences.[4]
In 1998, he was presented with the William B. Coley Award.