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.
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.
Hidenori
H
Yokoi
Oksoon H
OH
Choi
Walter
W
Hubbard
Hyun-Sil
HS
Lee
Brendan J
BJ
Canning
Hyun H
HH
Lee
Seung-Duk
SD
Ryu
Stephan
S
von Gunten
Carol A
CA
Bickel
Sherry A
SA
Hudson
Donald W
DW
Macglashan
Bruce S
BS
Bochner
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