SUMMARY A mutation in ORAI1, the gene encoding the pore-forming subunit of the Ca2+-release–activated Ca2+ (CRAC) channel, abrogates the store-operated entry of Ca2+ into cells and impairs lymphocyte activation. Stromal interaction molecule 1 (STIM1) in the endoplasmic reticulum activates ORAI1–CRAC channels. We report on three siblings from one kindred with a clinical syndrome of immunodeficiency, hepatosplenomegaly, autoimmune hemolytic anemia, thrombocytopenia, muscular hypotonia, and defective enamel dentition. Two of these patients have a homozygous nonsense mutation in STIM1 that abrogates expression of STIM1 and Ca2+ influx.

Background Defects in the development or activation of T cells result in immunodeficiency associated with severe infections early in life. T cell activation requires Ca2+ influx through Ca2+-release activated Ca2+ (CRAC) channels encoded by the gene ORAI1. Objective Investigation of the genetic causes and the clinical phenotype of immunodeficiency in patients with impaired Ca2+ influx and CRAC channel function. Methods DNA sequence analysis for mutations in the genes ORAI1, ORAI2, ORAI3, stromal interaction molecules (STIM) 1 and 2 as well as mRNA and protein expression analysis of ORAI1 in immunodeficient patients. Immunohistochemical analysis of ORAI1 tissue distribution in healthy human donors. Results We identified mutations in ORAI1 in patients from two unrelated families. One patient is homozygous for a nonsense mutation in ORAI1 (ORAI1-A88SfsX25) and a second patient is compound heterozygous for two missense mutations in ORAI1 (ORAI1-A103E/L194P). All three mutations abolish ORAI1 expression and impair Ca2+ influx and CRAC channel function. The clinical syndrome associated with ORAI1 deficiency is characterized by immunodeficiency with a defect in the function but not the development of lymphocytes, congenital myopathy and anhydrotic ectodermal dysplasia (EDA) with a defect in dental enamel calcification. In contrast to the limited clinical phenotype, we found ORAI1 protein expression in a wide variety of cell types and organs. Conclusion Ca2+ influx through ORAI1 is crucial for lymphocyte function in vivo. Despite almost ubiquitous ORAI1 expression, the channel has a non-redundant role in only a few cell-types judging from the limited clinical phenotype in ORAI1 deficient patients.

ORAI1 is the pore-forming subunit of the Ca2+ release-activated Ca2+ (CRAC) channel, which is responsible for store-operated Ca2+ entry in lymphocytes. A role for ORAI1 in T cell function in vivo has been inferred from in vitro studies of T cells from human immunodeficient patients with mutations in ORAI1 and Orai1−/− mice, but a detailed analysis of T cell-mediated immune responses in vivo in mice lacking functional ORAI1 has been missing. We therefore generated Orai1 knock-in mice (Orai1KI/KI) expressing a nonfunctional ORAI1-R93W protein. Homozygosity for the equivalent ORAI1-R91W mutation abolishes CRAC channel function in human T cells resulting in severe immunodeficiency. Homozygous Orai1KI/KI mice die neonatally, but Orai1KI/KI fetal liver chimeric mice are viable and show normal lymphocyte development. T and B cells from Orai1KI/KI mice display severely impaired store-operated Ca2+ entry and CRAC channel function resulting in a strongly reduced expression of several key cytokines including IL-2, IL-4, IL-17, IFN-γ, and TNF-α in CD4+ and CD8+ T cells. Cell-mediated immune responses in vivo that depend on Th1, Th2, and Th17 cell function were severely attenuated in ORAI1-deficient mice. Orai1KI/KI mice lacked detectable contact hypersensitivity responses and tolerated skin allografts significantly longer than wild-type mice. In addition, T cells from Orai1KI/KI mice failed to induce colitis in an adoptive transfer model of inflammatory bowel disease. These findings reaffirm the critical role of ORAI1 for T cell function and provide important insights into the in vivo functions of CRAC channels for T cell-mediated immunity.

T cell function is dependent on store-operated Ca2+ influx that is activated by the stromal interaction molecules (STIM) 1 and 2. We show that mice with T-cell specific deletion of STIM1 or STIM2 are protected from experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis. While STIM1- and STIM2-deficient T cells could be successfully primed by autoantigen, they failed to produce the proinflammatory cytokines IL-17 and IFN-γ. STIM1-deficient T cells showed reduced expression of IL- 23R, required for Th17 cell homeostasis, and had impaired chemokine dependent T cell migration caused by a lack of chemokine-induced Ca2+ influx. Autoantigen-specific STIM1- or STIM2-deficient T cells failed to expand and accumulate in the CNS and lymph nodes following adoptive transfer to passively induce EAE, suggesting that autoantigen-specific restimulation or homeostasis of STIM1- and STIM2-deficient T cells are impaired. Combined deletion of both STIM1 and STIM2, previously shown to impair Treg cell development and function, completely protected mice from EAE. This indicates that, in the absence of Ca2+ influx, autoreactive T cells are severely dysfunctional rendering Treg dispensable for the prevention of CNS inflammation. Our findings demonstrate that both STIM1 and STIM2 are critical for T cell function and autoimmunity in vivo.

During difficult tracheal intubation in children, direct laryngoscopy is an overly used technique with a low chance of success. GlideScope use was associated with a higher chance of success with no increased risk of complications. GlideScope use in children with difficult tracheal intubation has a lower success rate than in adults with difficult tracheal intubation. Children weighing less than 10 kilograms had lower success rates with either device. Attempts should be minimized with either device to decrease complications.