Natural killer cells and autoimmunity
Nature Immunology, pages 245-251.
Autoimmune diseases such as arthritis and myasthenia gravis are inflammatory disorders in which cells of the immune system attack the body’s own organs. The causes of autoimmune diseases are still unknown, but some theories postulate that they may be induced by an external trigger such as a viral infection.
Natural killer cells are the first line of defense in fighting infections and therefore could be involved in the initiation of autoimmune diseases. Natural killer cells come in two varieties, NK and NKT cells, but their precise role in the development of autoimmunity is unclear.
In the September issue of Nature Immunology [Vol. 1, No. 3], researchers from the Karolinska Institute in Stockholm, Sweden, used a mouse model of the autoimmune disease myasthenia gravis (in which the connections between nerves and muscles are attacked) to study the role played by NK and NKT cells. Myasthenia gravis is a well characterized autoimmune disease: CD4+ T cells help B cells to produce autoantibodies.
Ljünggren et al. show that NK cells, but not NKT cells, are required for the initial development of myasthenia gravis. Mice that had no NK cells, but not those that lacked NKT cells, did not activate T cells, so no B cells were instructed to make autoreactive antibodies. These data reveal a link between NK cells and autoreactive T and B cells that attack the host’s own body.
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