CCL2 is primarily secreted by monocytes, macrophages and dendritic cells. These progenitor cells initially transform into immature dendritic cells. This strongly attracts certain types of monocytes which differentiate into dendritic cells. The viruses infect, amongst others, monocytes, macrophages, Schwann cells, and dendritic cells. Furthermore, it is a receptor for phagocytosis on macrophages or dendritic cells. They engage in cross talk with other immune cells, like dendritic cells, neutrophils and lymphocytes. It also is found on monocytes and dendritic cells. ILCs do not express myeloid or dendritic cell markers. Langerin is a protein found in Langerhans cells, and dendritic cells. LAG3 is known to be involved in the maturation and activation of dendritic cells. Skin dendritic (or Langerhans) cells (DCs) are preferentially targeted. In other organisms, the function of dendritic cells can differ slightly. A lack of FLT3L results in low levels of dendritic cells. It exists in two forms, secreted and membrane-bound particularly on dendritic cells. However, there are differences in the cytokines produced depending on the type of dendritic cell.