The international team of researchers from the United States and France has discovered a mouse immune cell that functions as both assassin and messenger. This led to the race among scientists to find a human equivalent of this multitasking cell. Cells that could seek out and destroy cancer have to be designed.
Drew Pardoll, M.D., Ph.D., the Seraph Professor of Oncology at the Johns Hopkins Kimmel Cancer Center says that this cell has the ability to kill foreign pathogens and distribute information about that experience. He said that the cell speeds up the immune reactions and makes the system more efficient in removing the foreign material. The results were published in the journal Nature Medicine.Frank Housseau, Ph.D., research associate at Hopkins' Kimmel Cancer Center and member of Pardoll's immunology laboratory said that Interferon-producing killer dendritic cell (IKDC) which is very rare and is seen in the spleen also has similar features. Immune system works through cross linking and signaling among a variety of cells. One of the first immune cells that alert the immune system is a natural killer (NK) cell. NK cells poke holes in the invader's outer membrane. Then, NK cells inform the other immune cells, including dendritic cells. Dendritic cells spread information about the foreign invaders to other immune cells, but do not actually kill the invaders.
Housseau said that the outer membranes of the dendritic cells were studded with NK cells. This resulted in a NK-dendritic cell blend. This is a new stage that retains all the molecular characteristics of both NK and dendritic cells. These were called the Interferon-producing killer dendritic cell (IKDC).
IKDC produces both types of interferon proteins, normally secreted independently by NK and dendritic cells. He also found both NK and dendritic like molecules on the surface of IKDCs. Initially these cells behave like NK cell. After the cell encounters a pathogen, the cell switches roles from killer to dendritic like messenger. The cell sprouts long, hairy tentacles called dendrites. It uses its "arms" to increase the amount of surface area it reaches to communicate and interact with other immune cells. Then, the cell dies and is replenished by the bone marrow.
Researchers studied about these cells by fluorescent-tags and by infecting mice with bacteria called listeria. In assassin-mode, the IKDCs were found in the blood, lining of the gut, liver and other organs which were in close contact with the pathogen. In the lymph nodes they found approximately 35 % of the original group of IKDCs now secreting communication molecules signaling a switch to messenger-mode.
Housseau's colleagues in France, led by Laurence Zitvogel at the Institut Gustave Roussy, tested IKDCs in killing cancer cells. They injected mice with a cancer drug called Gleevec. This blocks an abnormal protein produced by cancer cells, and a growth factor for NK cells. The drug-growth factor combo served as a lure, leading the IKDCs to tumors implanted in the mice. The results were that tumors shrunk in mice, which received injections of IKDCs, but not in those receiving conventional NK cells only. Housseau's group is conducting further studies to verify the role of IKDC cells in infection and cancer.
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