When infected with Leishmania macrophages of the skin are activated best she knew how. This is due to the exchange of signals with eosinophils who support the “choice” of macrophages with secretion of interleukin 4 and interleukin 13. Work published in the journal Science Immunology.
Cutaneous leishmaniasis refers to “forgotten diseases”, — tropical diseases that affect mainly poor people in poor countries and attracted little attention from the press and researchers. According to the data of who for the last five years were infected more than a million people, and another billion living in risky from the point of view of the infected areas. Leishmaniasis is caused by protozoa of the genus Leishmania, which with the bite of a mosquito enter the human body and — in case of skin forms cause the appearance of ulcers. In the skin, these parasites live inside the cells of macrophages, which normally “protect” the skin, and the type of macrophages depends on the success of Leishmania.
There are two main types of cells that can become macrophages after activation: Pro-inflammatory M1 and Vice versa, “healing” M2. What way is the activation choose a macrophage depends on who activates it and what molecule uses for this. In the case of infection by bacteria and intracellular parasites, T-cells send a signal to the macrophages to become Pro-inflammatory, but instead at the infection site are M2 macrophages, which Leishmania feels more comfortable.
To understand why this is so, sang-Hoon Lee (Sang Hun Lee) and his colleagues from the National Institute of health in Bethesda found who activates macrophages when infected with Leishmania. Key driver for this is the molecule interleukin IL-4, but it is unable to secrete different cells. They created lines of mice with defective IL-4, which were manifested either in cells of innate immunity or acquired. Mice infected with Leishmania and then estimated the number of macrophages in each type. It turned out that IL-4 and also IL-13 with similar action of the macrophages supply the cells of innate immunity, eosinophils. In the absence of the contribution of eosinophils, macrophages switched in the proinflammatory state, their number is declining and damaging the results were less.