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Roland J, Soranzo L, Launay JM, Vargaftig B: [Demonstration of the immunoreactivity of polynuclear eosinophils for bombesin and substance P. Clin Chim Acta. 2003 May;331(1-2):103-10.
A new concept of the neuro-immune axis]. Immunoreactivity for B and SP was detected by means of light and electron microscopy (by preembedding immunocytochemistry), in eosiniphilic polymorphonuclear leukocytes infiltrating the connective tissue of gastrointestinal and respiratory tract in mouse, rat and human ; and in human bronchoalveolar lavages in case of hypereosinophilia. This positive reaction depends on the use of an acetic-acid-containing-fixative (minimum 48 hours), and is located in the granules of eosinophils at their membrane level, and on eosinophil plasma membranes. Eosinophil peroxidases (catalases) should not affect the immunocytochemical reaction, since heating during a paraplast embedding and sodium-azide in electron microscopy procedure destroyed these enzymes. The membrane-bound immunoreaction for B and SP, with very close structural similarity, suggested cross-reactivity between the two neuropeptides, with recognition of one or several epitopes by the polyclonal antisera. One of these epitopes is probably associated with the C-terminal sequence of B (with tachykinin-like activity) and seems to be present in other neuropeptides such as SP ; another epitope would be the N-terminal sequence of SP (with bradykinin-like activity). Hence, eosinophils could be the source of tachykinin and bradykinin. Another hypothesis about the membrane immunolocalization (as yet unproved experimentally) would be a cross-reactivity due to recognition of electron-negative charges of membrane phospholipides. Lysophosphatidic acid could play a hormone-like activity and mimic B and SP activities, such as growth factors. Finally, anti-B and anti-SP antisera could contain anti-idiotype antibodies uncovering receptors. In conclusion : eosinophils might produce neuropeptides or neuropeptide-like substances, with, for instance, bronchoconstrictive activity by paracrine control and possible complementarity with nerve endings. |
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