Mast cell activation is characterized by upregulation of a functional anaphylatoxin C5a receptor.
BACKGROUND
Mast cells (MC) are key effector cells of allergic diseases and resistance to helminthic parasites and induce or amplify diverse innate and adaptive immune responses. The signals controlling MC mobilization during inflammation are not fully understood.


RESULTS
Since anaphylatoxins are attractive candidates as MC chemoattractants, we investigated expression and function of anaphylatoxin receptors in murine MC. Precursor cell-derived MC cultured with IL-3 in the presence or absence of SCF did not express significant amounts of surface C5a receptor (C5aR) or C3a receptor (C3aR). MC required approximately 4 h of stimulation with Ag (DNP-albumin, following preincubation with IgE anti-DNP), ionomycin, or PMA to enable a strong chemotactic response towards C5a, paralleled by a distinct C5aR upregulation. Likewise, C5a induced intracellular calcium fluxes solely in activated MC. In contrast, C3a proved to be a weak MC chemotaxin and unable to increase intracellular calcium. Primary peritoneal MC did not express detectable amounts of anaphylatoxin receptors, however, similar to precursor cell-derived MC, stimulation with Ag or ionomycin for 4 h induced a prominent surface expression of C5aR whereas C3aR remained undetectable.


CONCLUSIONS
Collectively, our results suggest that Ag-dependent as well as -independent activation induces an inflammatory MC phenotype which is distinguished by neoexpression of a functional C5aR as a novel effector mechanism in MC-mediated pathogenesis.
Department of Cellular and Molecular Immunology, Georg-August-University Göttingen, Humboldtallee 34, D-37073 Göttingen, Germany. asoruri@gwdg.de
Afsaneh
A
Soruri
Jasmin
J
Grigat
Ziba
Z
Kiafard
Jörg
J
Zwirner
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002454:Cell Differentiation / Q000276:immunology; D002478:Cells, Cultured; D002633:Chemotaxis / Q000187:drug effects / Q000276:immunology; D015936:Complement C5a / Q000494:pharmacology; D004140:Dinitrophenols / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology; D007073:Immunoglobulin E / Q000494:pharmacology; D007249:Inflammation / Q000378:metabolism; D008407:Mast Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D044087:Receptor, Anaphylatoxin C5a / Q000096:biosynthesis* / Q000276:immunology; D011951:Receptors, Complement / Q000096:biosynthesis* / Q000276:immunology; D011994:Recombinant Proteins / Q000494:pharmacology; D012710:Serum Albumin, Bovine / Q000494:pharmacology; D015854:Up-Regulation
D004140:Dinitrophenols; D044087:Receptor, Anaphylatoxin C5a; D011951:Receptors, Complement; D011994:Recombinant Proteins; C085567:complement C3a receptor; C034638:dinitrophenyl-bovine serum albumin; D012710:Serum Albumin, Bovine; D007073:Immunoglobulin E; D015936:Complement C5a; D002118:Calcium