Besides their largely specific and abundant toxic granule proteins, their Charcot-Leyden crystals, DNA traps, and the release of leukotrienes, human eosinophils are often seen as affecting the immune response and tissue remodeling due to the release of numerous types of cytokines and growth factors. However, the extent of release and the functionality of such mediators, particularly from human eosinophils, remains uncertain. This article reviews the literature focused on cocultures of human eosinophils with other cell types to identify possible cytokines and growth factors secreted by eosinophils and their function(s) on epithelial cells, fibroblasts, lymphocytes, and endothelial cells. Models of coculture include direct cell-to-cell contact, separation with filters and the use of eosinophil conditioned media. These models identified cytokines and growth factors as potential eosinophilic factors impacting the behavior of other cell types. The expression of these factors in eosinophils was confirmed in multiple published transcriptome datasets using human blood and tissue eosinophils, which also allowed us to identify additional potentially important eosinophilic products. This review supports the idea that human eosinophils remain effector cells via their release of toxic proteins (i.e., EPX, ECP RNASE3, MBP PRG2), galectin-10 (CLC), DNA, leukotrienes, and they produce and release a set of cytokines and growth factors to affect their surroundings.
Esnault et al. (Thu,) studied this question.