Fig. 6. Dynamic roles of S100A4 in allergic skin inflammation based on a mouse model of allergy.

Allergic inflammation requires the sensitization of the immune system by allergens, resulting in the production of antigen-specific T cells. The interaction of DCs in the draining lymph node with T cells is a critical step that is dependent on S100A4. B cell maturation as a result of T cell–B cell crosstalk (for example, the release of T_H2 cytokines by T cells) leads to the production of IgE and IgG1 by plasma cells. Cytokines and chemokines released by T cells stimulate the migration of circulating granulocytes (for example, neutrophils and eosinophils) to the inflammatory site (skin). Differentiation of naïve T cells into CD8⁺ cytotoxic T cells will exacerbate the skin damage. Blue arrows indicate the flow of the allergic responses. Green arrows indicate the promotion of these processes by S100A4 (figure created by R. Männel).