Figure 3.

The expulsion response against microbiome and opportunistic pathogens. Following epithelial damage, microbiome migrates inside and beneath the epithelium, which consequently triggers cell migration and stimulation of the immune system. Activated immune cells including macrophages, DCs, mast cells, T and B cells, and ILCs migrate to the area and initiate a type 2 expulsion response with Th2 cells, IgE-producing B cells, ILC2, IL-4, IL-5, and IL-13 against opportunistic pathogens, commensals, allergens, and pollutants. The opportunistic pathogens include Staphylococcus aureus, Pneumococcus, Haemophilus, and Moraxella. The inflammatory response together with translocated microbiome and microbial dysbiosis leads to defects in epithelium repair, and misclosure of the barrier, which instigate a vicious cycle of leaky barriers and chronic inflammatory responses as well as microbial dysbiosis. DC, dendritic cell; EOS, eosinophil, IL, interleukin; ILC, innate lymphoid cell; M∅, macrophage; MC, mast cell.