Dominant activating RAC2 mutation with lymphopenia, immunodeficiency, and cytoskeletal defects.

Ras-related C3 botulinum toxin substrate 2 (RAC2), through interactions with reduced NAD phosphate oxidase component p67 phox , activates neutrophil superoxide production, whereas interactions with p21-activated kinase are necessary for fMLF-induced actin remodeling. We identified 3 patients with de novo RAC2[E62K] mutations resulting in severe T- and B-cell lymphopenia, myeloid dysfunction, and recurrent respiratory infections. Neutrophils from RAC2[E62K] patients exhibited excessive superoxide production, impaired fMLF-directed chemotaxis, and abnormal macropinocytosis. Cell lines transfected with RAC2[E62K] displayed characteristics of active guanosine triphosphate (GTP)-bound RAC2 including enhanced superoxide production and increased membrane ruffling. Biochemical studies demonstrated that RAC2[E62K] retains intrinsic GTP hydrolysis; however, GTPase-activating protein failed to accelerate hydrolysis resulting in prolonged active GTP-bound RAC2. Rac2+/E62K mice phenocopy the T- and B-cell lymphopenia, increased neutrophil F-actin, and excessive superoxide production seen in patients. This gain-of-function mutation highlights a specific, nonredundant role for RAC2 in hematopoietic cells that discriminates RAC2 from the related, ubiquitous RAC1.

X-linked carriers of chronic granulomatous disease: Illness, lyonization, and stability.

BACKGROUND: Chronic granulomatous disease (CGD) is characterized by recurrent life-threatening bacterial and fungal infections and aberrant inflammation. Mutations in CYBB cause X-linked CGD and account for 65% to 70% of cases in Western countries. OBJECTIVE: We sought to understand the clinical manifestations associated with the X-linked CGD carrier state. METHODS: We undertook a comprehensive retrospective study of 162 affected female subjects. We examined dihydrorhodamine 123 (DHR) oxidation data for percentage of X-chromosome inactivation. We correlated lyonization (%DHR+) with clinical features. Where possible, we followed %DHR+ values over time. RESULTS: Clinical data were available for 93 female subjects: %DHR+ values were 46% (mean) and 47% (median; SD, 24). Using the %DHR+ value as the criterion for X inactivation, 78% of patients had levels of inactivation of 20% to 80%, suggesting random inactivation that was independent of age. In contrast, carriers with CGD-type infections had median %DHR+ values of 8% (n = 14; range, 0.06% to 48%), and those with only autoimmune or inflammatory manifestations had median %DHR+ values of 39% (n = 31; range, 7.4% to 74%). Those with both infections and autoimmunity had low %DHR+ values (n = 6; range, 3% to 14%). A %DHR+ value of less than 10% was strongly associated with infections (odds ratio, 99). Strong association persisted when %DHR+ values were less than 20% (odds ratio, 12). Autoimmunity was not associated with %DHR+ values. In 2 sets of identical twins, the %DHR+ populations tracked closely over time. Although the %DHR+ populations were very similar between sisters, those between mothers and daughters were unrelated. CONCLUSIONS: A low %DHR+ value strongly predicts infection risk in X-linked CGD carriers, and the carrier state itself is associated with autoimmunity.

IKBKG (NEMO) 5' Untranslated Splice Mutations Lead to Severe, Chronic Disseminated Mycobacterial Infections.

Four patients with adult-onset, disseminated mycobacterial infection had 5' UTR mutations in IKBKG without clear physical stigmata of NEMO deficiency. These mutations caused decreased levels of NEMO protein and Toll-like receptor driven cytokine production. Three patients died from disseminated disease. These mutations may be missed by whole exome sequencing.

A unified metric of human immune health.

Immunological health has been challenging to characterize but could be defined as the absence of immune pathology. While shared features of some immune diseases and the concept of immunologic resilience based on age-independent adaptation to antigenic stimulation have been developed, general metrics of immune health and its utility for assessing clinically healthy individuals remain ill defined. Here we integrated transcriptomics, serum protein, peripheral immune cell frequency and clinical data from 228 patients with 22 monogenic conditions impacting key immunological pathways together with 42 age- and sex-matched healthy controls. Despite the high penetrance of monogenic lesions, differences between individuals in diverse immune parameters tended to dominate over those attributable to disease conditions or medication use. Unsupervised or supervised machine learning independently identified a score that distinguished healthy participants from patients with monogenic diseases, thus suggesting a quantitative immune health metric (IHM). In ten independent datasets, the IHM discriminated healthy from polygenic autoimmune and inflammatory disease states, marked aging in clinically healthy individuals, tracked disease activities and treatment responses in both immunological and nonimmunological diseases, and predicted age-dependent antibody responses to immunizations with different vaccines. This discriminatory power goes beyond that of the classical inflammatory biomarkers C-reactive protein and interleukin-6. Thus, deviations from health in diverse conditions, including aging, have shared systemic immune consequences, and we provide a web platform for calculating the IHM for other datasets, which could empower precision medicine.

Multiomics integration of 22 immune-mediated monogenic diseases reveals an emergent axis of human immune health.

Monogenic diseases are often studied in isolation due to their rarity. Here we utilize multiomics to assess 22 monogenic immune-mediated conditions with age- and sex-matched healthy controls. Despite clearly detectable disease-specific and "pan-disease" signatures, individuals possess stable personal immune states over time. Temporally stable differences among subjects tend to dominate over differences attributable to disease conditions or medication use. Unsupervised principal variation analysis of personal immune states and machine learning classification distinguishing between healthy controls and patients converge to a metric of immune health (IHM). The IHM discriminates healthy from multiple polygenic autoimmune and inflammatory disease states in independent cohorts, marks healthy aging, and is a pre-vaccination predictor of antibody responses to influenza vaccination in the elderly. We identified easy-to-measure circulating protein biomarker surrogates of the IHM that capture immune health variations beyond age. Our work provides a conceptual framework and biomarkers for defining and measuring human immune health.

MDS-associated mutations in germline GATA2 mutated patients with hematologic manifestations.

Germline mutation in GATA2 can lead to GATA2 deficiency characterized by a complex multi-system disorder that can present with many manifestations including variable cytopenias, bone marrow failure, myelodysplastic syndrome/acute myeloid leukemia (MDS/AML), and severe immunodeficiency. Penetrance and expressivity within families is often variable. There is a spectrum of bone marrow disease in symptomatic cytopenic patients ranging from hypocellular marrows without overt dysplasia to those with definitive MDS, AML, or chronic myelomonocytic leukemia. Relatives of probands with the same mutations may demonstrate minimal disease manifestations and normal marrows. A comprehensive clinical, hematological and genetic assessment of 25 patients with germline GATA2 mutation was performed. MDS-associated mutations were identified in symptomatic GATA2 patients both with overt MDS and in those with hypocellular/aplastic bone marrows without definitive dysplasia. Healthy relatives of probands harboring the same germline GATA2 mutations had essentially normal marrows that were overall devoid of MDS-associated mutations. The findings suggest that abnormal clonal hematopoiesis is a common event in symptomatic germline mutated GATA2 patients with MDS and also in those with hypocellular marrows without overt morphologic evidence of dysplasia, possibly indicating a pre-MDS stage warranting close monitoring for disease progression.