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Original Article |
Receptor IIImediated Systemic Anaphylaxis but Not for the Arthus Reaction
Correspondence to: Toshiyuki Takai, Dept. of Experimental Immunology, Institute of Development, Aging and Cancer, Tohoku University, 4-1 Seiryo, Sendai 980-8575, Japan. Tel:81-22-717-8501 Fax:81-22-717-8505 E-mail:tostakai{at}idac.tohoku.ac.jp.
The Src family kinase Lyn initiates intracellular signal transduction by associating with a variety of immune receptors such as antigen receptor on B cells and high-affinity Fc receptor (FcR) for immunoglobulin Ig(E) (Fc
RI) on mast cells. Involvement of Lyn in the IgE-mediated immediate-type hypersensitivity is well documented, but the physiological significance of Lyn in IgG-dependent, type III low-affinity FcR for IgG (Fc
RIII)-mediated responses is largely unknown. In this study, we generated a double-mutant mouse strain deficient in both type II FcR for IgG (Fc
RIIB) and Lyn to exclude any involvement of inhibitory signaling by Fc
RIIB, which otherwise downregulates Fc
RIII-mediated cellular responses. Fc
RIIB-deficient but Lyn-sufficient mice served as controls. The Lyn deficiency attenuated IgG-mediated systemic anaphylaxis in vivo, and significantly reduced calcium mobilization and degranulation responses of bone marrowderived mast cells (BMMCs) in vitro. However, we found that either interleukin 4 or tumor necrosis factor
release by BMMCs was comparable to that from Lyn-deficient and control mice, and the reverse-passive Arthus reaction was equally induced in both mutant mice, indicating that Lyn is not involved in the onset of the IgG-mediated, Fc
RIII-dependent late phase responses of mast cells. These findings provide us with insight into distinct signaling mechanisms in mast cells underlying the development of diverse pathologies as well as a therapeutic potential for selective treatment of allergic disorders.
Key Words: Lyn, Fc receptor, hypersensitivity, mast cells, Arthus reaction
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