Ryanodine receptor (RyR) is a Ca(2+) channel that mediates Ca(2+) release from 
intracellular stores. Altered Ca(2+) homeostasis in skeletal muscle which 
usually occurs as a result of point mutations in type 1 RyR1 (RyR1) is a key 
molecular event triggering malignant hyperthermia (MH). There are three RyR 
isoforms, and we herein show, for the first time, that human dendritic cells 
(DCs) preferentially express RyR1 mRNA among them. The RyR activator, 
4-chloro-m-cresol (4CmC), induced Ca(2+) release in DCs, and this response was 
eliminated by dantrolene, an inhibitor of the RyR1, and was unaffected by 
xestospongin C, a selective inhibitor of IP(3) receptor. Activation of RyR1 
reduced LPS-induced IL-10 production, promoted the expression of HLA-DR and 
CD86, and thereby exhibited an improved capacity to stimulate allogeneic T 
cells. These findings demonstrate that RyR1-mediated calcium signaling modifies 
diverse DC responses and suggest the feasibility of using DC preparations for 
the diagnosis of MH.