Dear Colleagues,

Twenty to thirty percent of populations in the industrialized world are affected by allergies. Allergies have thereby become one of the major medical issues of the 21st century. The majority of these allergies belong to IgE-mediated allergies, where IgE, mast cells, and basophils are key players.

One of the major questions to address in this Special Issue of IJMS is why we have this system of cells and molecules that causes us so many problems. A second key question concerns what the central functions are of these cells and molecules in our immune system and how they have evolved during vertebrate evolution.

The first traces of mast cell-like cells have been found in sea squirt, a tunicate, where test cells express histamine, heparin, and a tryptic serine protease. All three of these are characteristic features of human and murine mast cells. Carboxypeptidase, another characteristic feature of human and murine mast cells, has also been identified in zebrafish mast-cell like cells. IgE only exists in mammals and has been found to have a very similar structure in all extant mammalian lineages, i.e., monotremes, marsupials, and placental mammals. The question here is whether other isotypes have a similar mast cell-activating function in reptiles, birds, amphibians, and fish. By in depth analysis of mast cells, basophils, and potential immunoglobulin binding receptors on mast cells and basophils in non-mammalian species, we will hopefully obtain a better picture of their evolutionarily conserved functions in our immune system and how they have become so deregulated in humans and several domestic animals. We also encourage people working with functions associated with Fc receptors, IgE, mast cells, and basophils in mammals to submit their findings to this issue of IJMS as it forms a solid base for comparative studies of these components of our immune system and how they have appeared and diversified during vertebrate evolution. Studies in other directions—for example, the presence of non-immunoglobulin-related receptors and their role in mast cell activation, such as the substance P receptors of the Mrgp family or the anaphylatoxin receptors, and when they have appeared and diversified during vertebrate evolution—are also highly encouraged.

Prof. Lars Hellman
Guest Editor

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• Mast cells
• Basophils
• Neutrophils
• Serine Protease
• Cleavage specificity
• Phage Display
• IgE
• Evolution
• Transcriptome
• Atopic Allergies