We investigated the molecular and cellular basis of severe combined immunodeficiency (SCID) in six patients with otofaciocervical syndrome type 2 who failed to attain T cell reconstitution after allogeneic hematopoietic stem cell transplantation, despite successful engraftment in three of them. We identified rare biallelic PAX1 rare variants in all patients. We demonstrated that these mutant PAX1 proteins have an altered conformation and flexibility of the paired box domain and reduced transcriptional activity. We generated patient-derived induced pluripotent stem cells and differentiated them into thymic epithelial progenitor cells and found that they have an altered transcriptional profile, including for genes involved in the development of the thymus and other tissues derived from pharyngeal pouches. These results identify biallelic, loss-of-function PAX1 mutations as the cause of a syndromic form of SCID due to altered thymus development.

Major histocompatibility complex class II (MHC II) deficiency is a rare combined immunodeficiency disease. Allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative treatment. Between June 1994 and February 2007, 30 children with MHC II deficiency underwent a total of 33 HSCT procedures. Median age at HSCT was 27 months. The stem cell source was unmanipulated bone marrow from HLA-identical related donors in 26 patients, one HLA antigen-mismatched bone marrow in 3 patients, and unrelated umbilical cord blood in 1 patient. Conditioning was with one of 3 myeloablative regimens--regimen A (18 patients): busulfan (Bu), cyclophosphamide (Cy), and etoposide; regimen B (2 patients): Bu, Cy, and antithymocyte globulin (ATG); or regimen C (1 patient): CY and total body irradiation (TBI)--or with a reduced-intensity regimen (12 patients): fludarabine, melphalan, and ATG. The median CD34 cell dose was 8.3 x 10(6)/kg. Twenty patients experienced immune reconstitution and had sustained engraftment ranging from 9% to 100% for lymphoid lines and from 5% to 100% for myeloid lines that were significant to cure the disease. The overall disease-free survival rate was 66% and 76% after HLA-identical HSCT, with a median follow-up of 6.3 years, which is higher than previously reported. In HLA-identical transplant recipients, reliable donor stem cell engraftment and immune reconstitution were achieved through myeloablative or reduced-intensity conditioning. Further studies and long-term follow-up are needed to determine the appropriate conditioning regimen.

Background: Hyper-IgE syndromes (HIES) are a clinically overlapping, heterogeneous group of inborn errors of immunity characterized by elevated serum IgE level, eosinophilia, atopy, and immune dysregulation. Deficiency of DOCK8 protein is potentially a life-threatening autosomal recessive HIES and only curable with bone marrow transplantation. Hence, the diagnosis of DOCK8 deficiency is critical and should be sought at an early stage to initiate definitive therapy.Methods: Serum samples from patients with DOCK8 deficiency and atopic dermatitis were profiled on a cytokine/chemokine panel for potential differential expression.Results: CXCL10 and TNF-A were upregulated in DOCK8 patients when compared to AD, possibly contributing toward increased susceptibility to infections and cancer.In contrast, epidermal growth factor (EGF) was significantly downregulated in a subgroup of DOCK8-deficient and AD patients, while IL-31 expression was comparable between both DOCK8-deficient and AD cohorts, possibly contributing toward pruritus seen in both groups.Conclusion: This comprehensive cytokine profile in HIES patients reveals distinctive biomarkers that differentiate between the DOCK8-deficient and AD patients. The unique expression profile of various inflammatory cytokines in patients with DOCK8 deficiency vs atopic dermatitis likely reflects disease-specific perturbations in multiple cellular processes and pathways leading to a predisposition to infections and allergies seen in these patients. These data agree with the role for EGF replacement therapy in EGF-deficient individuals with AD as well as DOCK8 deficiency through a potential shared pathway. In addition, these novel biomarkers may be potentially useful in distinguishing DOCK8 deficiency from AD allowing early-targeted treatment options. K E Y W O R D S atopic dermatitis, CXCL10, DOCK8, epidermal growth factor, hyper-IgE syndrome Abbreviations: EGF, epidermal growth factor; EPAS1, endothelial PAS domain protein 1; GCSF, CSF3 is colony-stimulating factor3; HIES, hyper-IgE syndrome; IL-31, interleukin-31; MDC, macrophage-derived chemokine; OPLS-DA, orthogonal projections to latent structures discriminant analysis; PGM3, phosphoglucomutase 3; STAT3, signal transducer activator of transcription 3; TNF, tumor necrosis factor.

Background: The gene AK2 encodes the phosphotransferase adenylate kinase 2 (AK2). Human variants in AK2 cause reticular dysgenesis, a severe combined immunodeficiency with agranulocytosis, lymphopenia, and sensorineural deafness that requires hematopoietic stem cell transplantation for survival. Objective: We investigated the mechanisms underlying recurrent sinopulmonary infections and hypogammaglobulinemia in 15 patients, ranging from 3 to 34 years of age, from 9 kindreds. Only 2 patients, both of whom had mildly impaired T-cell proliferation, each had a single clinically significant opportunistic infection. Methods: Patient cells were studied with next-generation DNA sequencing, tandem mass spectrometry, and assays of lymphocyte and mitochondrial function. Results: We identified 2 different homozygous variants in AK2. AK2 G100S and AK2 A182D permit residual protein expression, enzymatic activity, and normal numbers of neutrophils and lymphocytes. All but 1 patient had intact hearing. The patients' B cells had severely impaired proliferation and in vitro immunoglobulin secretion. With activation, the patients' B cells exhibited defective mitochondrial respiration and impaired regulation of mitochondrial membrane potential and quality. Although activated T cells from the patients with opportunistic infections demonstrated impaired mitochondrial function, the mitochondrial quality in T cells was preserved. Consistent with the capacity of activated T cells to utilize nonmitochondrial metabolism, these findings revealed a less strict cellular dependence of T-cell function on AK2 activity. Chemical inhibition of ATP synthesis in control T and B cells similarly demonstrated the greater dependency of B cells on mitochondrial function. Conclusions: Our patients demonstrate the in vivo sequelae of the cell-specific requirements for the functions of AK2 and mitochondria, particularly in B-cell activation and antibody production.