Inhibition of FcepsilonRI-dependent mediator release and calcium flux from human mast cells by sialic acid-binding immunoglobulin-like lectin 8 engagement.
BACKGROUND
Sialic acid-binding immunoglobulin-like lectins (Siglecs) are a family of glycan-binding inhibitory receptors, and among them, Siglec-8 is selectively expressed on human eosinophils, basophils, and mast cells. On eosinophils, Siglec-8 engagement induces apoptosis, but its function on mast cells is unknown.


OBJECTIVE
We sought to study the effect of Siglec-8 engagement on human mast cell survival and mediator release responses.


METHODS
Human mast cells were generated from CD34+ precursors. Apoptosis was studied by using flow cytometry. Mast cell mediator release or human lung airway smooth muscle contraction was initiated by FcepsilonRI cross-linking with or without preincubation with Siglec-8 or control antibodies, and release of mediators was analyzed along with Ca++ flux. RBL-2H3 cells transfected with normal and mutated forms of Siglec-8 were used to study how Siglec-8 engagement alters mediator release.


RESULTS
Siglec-8 engagement failed to induce human mast cell apoptosis. However, preincubation with Siglec-8 mAbs significantly (P < .05) inhibited FcepsilonRI-dependent histamine and prostaglandin D(2) release, Ca++ flux, and anti-IgE-evoked contractions of human bronchial rings. In contrast, release of IL-8 was not inhibited. Siglec-8 ligation was also shown to inhibit beta-hexosaminidase release and Ca++ flux triggered through FcepsilonRI in RBL-2H3 cells transfected with full-length human Siglec-8 but not in cells transfected with Siglec-8 containing a tyrosine to phenylalanine point mutation in the membrane-proximal immunoreceptor tyrosine-based inhibitory motif domain.


CONCLUSIONS
These data represent the first reported inhibitory effects of Siglec engagement on human mast cells.
Yokoi
Hidenori
H
Department of Medicine, Division of Allergy and Clinical Immunology, Johns Hopkins University School of Medicine, and the Johns Hopkins Asthma and Allergy Center, Baltimore, MD 21224, USA.
Choi
Oksoon H
OH
Hubbard
Walter
W
Lee
Hyun-Sil
HS
Canning
Brendan J
BJ
Lee
Hyun H
HH
Ryu
Seung-Duk
SD
von Gunten
Stephan
S
Bickel
Carol A
CA
Hudson
Sherry A
SA
Macglashan
Donald W
DW
Bochner
Bruce S
BS
D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000235:genetics / Q000378:metabolism*; D001980:Bronchi / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D006636:Histamine Release; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism; D037102:Lectins / Q000235:genetics / Q000378:metabolism*; D008407:Mast Cells / Q000378:metabolism* / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology; D009130:Muscle, Smooth / Q000502:physiology; D015230:Prostaglandin D2 / Q000378:metabolism; D017455:Receptors, IgE / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014162:Transfection; D001619:beta-N-Acetylhexosaminidases / Q000378:metabolism
D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; D016209:Interleukin-8; D037102:Lectins; C502447:MS4A2 protein, human; D017455:Receptors, IgE; C403967:SIGLEC8 protein, human; D001619:beta-N-Acetylhexosaminidases; D015230:Prostaglandin D2; D002118:Calcium