Ultrastructural evidence for human mast cell-eosinophil interactions in vitro

Abstract

We have hypothesized that mast cells (MC) and eosinophils (Eos), the main effectors of allergy, can form an effector unit. These cells co-exist in the inflamed tissues during the late and chronic stages of allergy and have been shown to be capable of influencing each other's survival and activity via soluble mediators. We have recently described couples of receptor-ligands that are expressed on either/both of these cells and that imply a physical interaction. In this study, we have investigated the existence of short-term (60 min) in vitro interactions between human peripheral blood Eos and cord-blood-derived MC by transmission electron microscopy. We have found that MC and Eos adhere to each other; the lipid body content and the granule morphology of co-cultured MC and Eos, respectively, are altered, and the level of Eos peroxidase (EPO) released by co-cultured Eos is elevated. Moreover, the transfer of EPO from Eos to MC and tryptase from MC to Eos has been observed. Our results thus indicate that, when co-cultured, MC and Eos show signs of physical contact and of reciprocal activation. This is the first in vitro evidence of functional physical interactions between human MC and Eos, interactions that might also occur in vivo during allergic diseases.

Lipid body formation during maturation of human mast cells

“…Recently, human cord blood-derived mast cells have been reported to contain LBs after in vitro differentiation and cultivation in the presence of 10% fetal bovine serum ( 33 ). Here, the mast cells were differentiated in serum-free medium, which contained 1% (140 M) fatty acid-containing BSA.…”

The Regulatory Function of Eosinophils

“…The eosinophil–mast-cell interaction was highlighted by a recent clinical study showing that in human patients with the allergic GI disorder EoE, eosinophils are physically coupled with mast cells as assessed by immunohistochemistry (84) and are a major source of the mast cell–supporting cytokine IL-9 (85). In vitro ultra-structural evidence also indicated that eosinophils and mast cells form cell-cell contact and exchange their products for reciprocal activation (84, 86). Importantly, anti–IL-5 therapy concomitantly reduced both eosinophils and mast cell numbers (84), indicating that eosinophils promote mastocytosis in human allergic disease.…”

NOD1 and NOD2 Interact with the Phagosome Cargo in Mast Cells: A Detailed Morphological Evidence

“…As previously described [36], samples were washed twice with sodium cacodylate buffer (pH 7.4) and then postfixed with 1 % OsO 4 for 1 h at 4°C. Postfixed cells were dehydrated with a graded ethanol series ending with 100 % ethanol and then embedded in Dow Epoxy Resin (DER 332; Unione Chimica Europea, Milan, Italy) and DER732 (Serva, Heidelberg, Germany).…”