1.2.7　Immune function

The skin is the largest tissue organ of the human body，constituting the immune barrier between the body and the external environment，and is also an important immune organ.The functions of the skin immune system include：①innate immune function，such as tight junctions between keratinocytes to form a cell barrier；phagocytosis，dissolution and killing of pathogenic microorganisms of macrophages；cytolysis of complement；②adaptive immune function，refers to the antigen presentation effect of keratinocytes，Langerhans cells，and dermal dendritic cells；the effect of T cells and their subgroups；and the effect of immune molecules（e.g.，cytokines and antibodies）.It has been discovered that vascular endothelial cells and fibroblasts in the dermis can also participate in the skin immune response.The skin can effectively initiate an immune response and restore and maintain immune homeostasis in time to avoid immune pathological damage，and skin immune function disorders can lead to disease states.The skin completes its immune function with a variety of immune cell components and a large number of immune molecules.(https://www.daowen.com)