Successful bone marrow transplantation for IPEX syndrome after reduced-intensity conditioning.

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is a rare, fatal autoimmune disorder caused by mutations in the FOXP3 gene leading to the disruption of signaling pathways involved in regulatory T-lymphocyte function. Lifelong multiagent immunosuppression is necessary to control debilitating autoimmune manifestations such as colitis and food allergies. Allogeneic hematopoietic stem cell transplantation (HSCT) can restore T-cell regulatory function but has been previously associated with poor outcome. We describe successful HSCT in 4 patients with IPEX syndrome using a novel reduced-intensity conditioning regimen that resulted in stable donor engraftment, reconstitution of FOXP3+ T regulatory CD4+ cells, and amelioration of gastrointestinal symptoms.

Patients of African ancestry with hemophagocytic lymphohistiocytosis share a common haplotype of PRF1 with a 50delT mutation.

Mutations of the perforin gene (PRF1) are present in a proportion of patients with hemophagocytic lymphohistiocytosis (HLH). We found that all identified infants with HLH of African descent (17 from USA, 4 from Europe) have 50delT-PRF1 (16 homozygotes, 5 compound heterozygotes), accounting for the most frequently observed PRF1 mutation. Two additional patients with HLH, self-reporting as Hispanic, carried 50delT, but no Caucasians were identified with 50delT. To test the hypothesis that this mutation represents a single haplotype, DNA from 23 patients with HLH and 30 African-American control subjects was sequenced for the PRF1 gene, including portions of the intron containing known single nucleotide polymorphisms (SNPs). The same groups were genotyped at 3 microsatellites proximal to PRF1. The SNP profiles of patients with 50delT-PRF1 were identical, and 5 novel SNPs were identified among African-American control subjects. Patients with 50delT-PRF1 were also found to have had an earlier age of disease onset than patients with other PRF1 mutations. Extent of haplotype sharing and variability of microsatellite alleles in 50delT-PRF1 chromosomes suggest that this mutation arose approximately 1000 to 4000 years ago and is restricted to patients of African descent.

Signalling during hypoxia in human T lymphocytes--critical role of the src protein tyrosine kinase p56Lck in the O2 sensitivity of Kv1.3 channels.

T lymphocytes encounter hypoxia when they migrate to pathological sites such as tumours and wounds. The inability of T cells to provide an efficient defence at these sites can in part be explained by the hypoxic environment. Kv 1.3 channels, important components of the T cell activation process are inhibited by hypoxia and their inhibition accounts for a hypoxia-induced decrease in T cell proliferation. Although Kv 1.3 channels play a key role in T cell O(2) sensing, the signalling mechanisms mediating their response to hypoxia are still not understood. In this study, we show that the src-protein tyrosine kinase p56Lck (Lck) is required for Kv 1.3 channel response to hypoxia. Pre-exposure to the src inhibitor PP2 abolished the hypoxia-induced inhibition of Kv 1.3 channels in primary human T lymphocytes. Moreover, Kv 1.3 channel sensitivity to hypoxia was lost in Lck-deficient Jurkat T cells. Further studies with recombinant Kv 1.3 channels showed that Kv 1.3 channels lack intrinsic O(2) sensitivity, but delivery of Lck into the cells and transfection of a constitutively active Lck (Y505FLck) restored their sensitivity to hypoxia. Although Lck is necessary for the Kv 1.3 channel response to hypoxia, it does not directly inhibit Kv 1.3 channels. Indeed, under normal oxygen tension, delivery of active Lck into L929 cells and overexpression of Y505FLck did not decrease recombinant Kv 1.3 currents. On the contrary, activation of endogenous src kinases increased wild-type Kv 1.3 currents in T lymphocytes. Our findings indicate that Lck is required for the acute response to hypoxia of human T lymphocytes as it is necessary to confer O(2) sensitivity on Kv 1.3 channels.

Rapid detection of intracellular SH2D1A protein in cytotoxic lymphocytes from patients with X-linked lymphoproliferative disease and their family members.

Mutations in the SH2D1A gene have been described in most patients with the clinical syndrome of X-linked lymphoproliferative disease (XLP). The diagnosis of XLP is still difficult given its clinical heterogeneity and the lack of a readily available rapid diagnostic laboratory test, particularly in patients without a family history of XLP. XLP should always be a consideration in males with Epstein-Barr virus-associated hemophagocytic lymphohistiocytosis (EBV-HLH). Four-color flow cytometric analysis was used to establish normal patterns of SH2D1A protein expression in lymphocyte subsets for healthy subjects. Three of 4 patients with XLP, as confirmed by the detection of mutations in the SH2D1A gene, had minimal intracellular SH2D1A protein in all cytotoxic cell types. The remaining patient lacked intracellular SH2D1A protein in CD56+ natural killer (NK) and T lymphocytes and had an abnormal bimodal pattern in CD8+ T cells. Carriers of SH2D1A mutations had decreased SH2D1A protein staining patterns compared with healthy controls. Eleven males with clinical syndromes consistent with XLP, predominantly EBV-HLH, had patterns of SH2D1A protein expression similar to those of healthy controls. Four-color flow cytometry provides diagnostic information that may speed the identification of this fatal disease, differentiating it from other causes of EBV-HLH.