Evaluation of Genetic or Cellular Impairments in Type I IFN Immunity in a Cohort of Young Adults with Critical COVID-19.

Several genetic and immunological risk factors for severe COVID-19 have been identified, with monogenic conditions relating to 13 genes of type I interferon (IFN) immunity proposed to explain 4.8% of critical cases. However, previous cohorts have been clinically heterogeneous and were not subjected to thorough genetic and immunological analyses. We therefore aimed to systematically investigate the prevalence of rare genetic variants causing inborn errors of immunity (IEI) and functionally interrogate the type I IFN pathway in young adults that suffered from critical COVID-19 yet lacked comorbidities. We selected and clinically characterized a cohort of 38 previously healthy individuals under 50 years of age who were treated in intensive care units due to critical COVID-19. Blood samples were collected after convalescence. Two patients had IFN-α autoantibodies. Genome sequencing revealed very rare variants in the type I IFN pathway in 31.6% of the patients, which was similar to controls. Analyses of cryopreserved leukocytes did not indicate any defect in plasmacytoid dendritic cell sensing of TLR7 and TLR9 agonists in patients carrying variants in these pathways. However, lymphocyte STAT phosphorylation and protein upregulation upon IFN-α stimulation revealed three possible cases of impaired type I IFN signaling in carriers of rare variants. Together, our results suggest a strategy of functional screening followed by genome analyses and biochemical validation to uncover undiagnosed causes of critical COVID-19.

Phosphorylation of intracellular signalling molecules in peripheral blood cells from patients with psoriasis on originator or biosimilar infliximab.

BACKGROUND: Psoriasis vulgaris is a chronic, inflammatory skin disease characterized by a dysregulated immune response and it is associated with substantial systemic comorbidities. Biological drugs such as tumour necrosis factor (TNF)-α inhibitors can ameliorate the disease but are expensive. Biosimilar drugs have the same amino-acid sequence as the originator, but differences in manufacturing can affect biological activity, efficacy and tolerability. OBJECTIVES: To explore potential differences in intracellular phosphorylation of signalling molecules in peripheral blood cells from patients with psoriasis treated with the TNF-α inhibitor infliximab compared with healthy controls, and to investigate if the phosphorylation pattern was influenced by switching from the originator infliximab to the biosimilar CT-P13. METHODS: By flow cytometry, we measured phosphorylation of nuclear factor kappa B, extracellular signal-regulated kinase 1/2, p38 mitogen-activated protein kinase and signal transducer and activator of transcription 3, before and after TNF-α stimulation in monocytes and T, B, natural killer and CD3+  CD56+ cells from 25 patients with psoriasis treated with infliximab and 19 healthy controls. RESULTS: At inclusion, phosphorylation levels of peripheral blood mononuclear cells (PBMCs) were increased in patients with psoriasis compared with healthy controls, even though clinical remission had already been achieved. Phosphorylation levels declined in patients on both originator infliximab and biosimilar during continued treatment. No significant differences were detected between the two medications after 12 months. CONCLUSIONS: Patients with psoriasis on infliximab have higher activation levels of PBMCs than do healthy controls, possibly reflecting systemic inflammation. Switching from the originator infliximab to biosimilar CT-P13 did not affect phosphorylation levels or clinical parameters, suggesting that CT-P13 is a noninferior treatment alternative to the originator infliximab.

Patients with Primary Sjögren's Syndrome Have Alterations in Absolute Quantities of Specific Peripheral Leucocyte Populations.

An accurate dissection of peripheral blood enumeration is lacking in primary Sjögren's syndrome (pSS). The purpose of this study was to quantify different leucocyte populations in peripheral blood of patients with pSS. Numbers of specific leucocyte subsets were determined in 86 pSS patients and 74 healthy donors quantifying 21 distinct subtypes by flow cytometry. Subgroups of pSS patients were stratified based on presence of extraglandular manifestations (EGMs) and SSA/SSB autoantibodies. Overall, pSS patients manifested decreased lymphocyte subpopulations compared to healthy donors. Such decreases were more pronounced in SSA/SSB positive patients and patients with EGM. Granulocyte and monocyte subpopulations were increased in pSS patients compared to healthy donors, with the greatest increases in SSA/SSB positive patients. Unsupervised hierarchal clustering based on cell quantities was used to further subgroup the pSS patients into four clusters. One of the clusters characterized by higher concentrations of NKT cells, CD56hi NK cells, CD20+ CD38- B cells and CD8+ CD38- T cells was associated with weaker clinical symptoms than the other clusters, possibly marking a milder disease phenotype. In conclusion, our analyses indicate significant alterations in the cellular profiles of peripheral blood leucocytes in patients with pSS and may help to stratify the patients according to disease severity.

Increased proportion of mature NK cells is associated with successful imatinib discontinuation in chronic myeloid leukemia.

Recent studies suggest that a proportion of chronic myeloid leukemia (CML) patients in deep molecular remission can discontinue the tyrosine kinase inhibitor (TKI) treatment without disease relapse. In this multi-center, prospective clinical trial (EURO-SKI, NCT01596114) we analyzed the function and phenotype of T and NK cells and their relation to successful TKI cessation. Lymphocyte subclasses were measured from 100 imatinib-treated patients at baseline and 1 month after the discontinuation, and functional characterization of NK and T cells was done from 45 patients. The proportion of NK cells was associated with the molecular relapse-free survival as patients with higher than median NK-cell percentage at the time of drug discontinuation had better probability to stay in remission. Similar association was not found with T or B cells or their subsets. In non-relapsing patients the NK-cell phenotype was mature, whereas patients with more naïve CD56bright NK cells had decreased relapse-free survival. In addition, the TNF-α/IFN-γ cytokine secretion by NK cells correlated with the successful drug discontinuation. Our results highlight the role of NK cells in sustaining remission and strengthen the status of CML as an immunogenic tumor warranting novel clinical trials with immunomodulating agents.

CD56dimCD57+NKG2C+ NK cell expansion is associated with reduced leukemia relapse after reduced intensity HCT.

We have recently described a specialized subset of human natural killer (NK) cells with a CD56(dim)CD57(+)NKG2C(+) phenotype that expand specifically in response to cytomegalovirus (CMV) reactivation in hematopoietic cell transplant (HCT) recipients and exhibit properties characteristic of adaptive immunity. We hypothesize that these cells mediate relapse protection and improve post-HCT outcomes. In 674 allogeneic HCT recipients, we found that those who reactivated CMV had lower leukemia relapse (26% (17-35%), P=0.05) and superior disease-free survival (DFS) (55% (45-65%) P=0.04) 1 year after reduced intensity conditioning (RIC) compared with CMV seronegative recipients who experienced higher relapse rates (35% (27-43%)) and lower DFS (46% (38-54%)). This protective effect was independent of age and graft-vs-host disease and was not observed in recipients who received myeloablative regimens. Analysis of the reconstituting NK cells demonstrated that CMV reactivation is associated with both higher frequencies and greater absolute numbers of CD56(dim)CD57(+)NKG2C(+) NK cells, particularly after RIC HCT. Furthermore, expansion of these cells at 6 months posttransplant independently trended toward a lower 2-year relapse risk. Together, our data suggest that the protective effect of CMV reactivation on posttransplant relapse is in part driven by adaptive NK cell responses.

Reduced DNAM-1 expression on bone marrow NK cells associated with impaired killing of CD34+ blasts in myelodysplastic syndrome.

Myelodysplastic syndromes (MDS) comprise a heterogeneous group of clonal stem-cell disorders characterized by ineffective hematopoiesis and risk of progression to acute myeloid leukemia. Increased apoptosis and suppressed functions of peripheral blood natural killer (NK) cells have been described in MDS patients, but only limited information is available on the phenotypic and functional integrity of NK cells in the bone marrow. In a cohort of 41 patients with distinct clinical subtypes of MDS, we here show that NK cells in the bone marrow show decreased surface expression of the activating receptors DNAM-1 and NKG2D. Notably, decreased receptor expression correlated with elevated bone marrow blast counts and was associated with impaired NK-cell responsiveness to stimulation with the K562 cell line, or co-activation by NKG2D or DNAM-1 in combination with the 2B4 receptor. Furthermore, antibody-masking experiments revealed a central role for DNAM-1 in NK cell-mediated killing of freshly isolated MDS blasts. Thus, given the emerging evidence for NK cell-mediated immune surveillance of neoplastic cells, we speculate that reduced expression of DNAM-1 on bone marrow NK cells may facilitate disease progression in patients with MDS.

Spectrum, and clinical and functional implications of UNC13D mutations in familial haemophagocytic lymphohistiocytosis.

OBJECTIVE: Familial haemophagocytic lymphohistiocytosis (FHL) is a fatal disorder of immune dysregulation with defective cytotoxic lymphocyte function. Disease-causing mutations have been identified in the genes encoding perforin (PRF1), syntaxin-11 (STX11), and Munc13-4 (UNC13D). We screened for UNC13D mutations and studied clinical and functional implications of such mutations in a well defined patient cohort. METHODS: Sequencing of UNC13D was performed in 38 FHL patients from 34 FHL families in which PRF1 and STX11 mutations had been excluded. RESULTS: We identified six different mutations affecting altogether 9/38 individuals (24%) in 6/34 (18%) unrelated PRF1/STX11-negative families. Four novel mutations were revealed; two homozygous nonsense mutations (R83X and W382X), one splice mutation (exon 28), and one missense mutation (R928P). In addition, two known mutations were identified (R214X and a deletion resulting in a frame-shift starting at codon 782). There was considerable variation in the age at diagnosis, ranging from time of birth to 14 years (median 69 days). Three of nine patients (33%) developed central nervous system (CNS) symptoms. Natural killer (NK) cell activity was impaired in all four patients studied. Defective cytotoxic lymphocyte degranulation was evident in the two patients investigated, more pronounced in the patient with onset during infancy than in the patient with adolescent onset. CONCLUSIONS: Biallelic UNC13D mutations were found in 18% of the PRF1/STX11-negative FHL families. Impairment of NK cell degranulation was less pronounced in a patient with adolescent onset. FHL should be considered not only in infants but also in adolescents, and possibly young adults, presenting with fever, splenomegaly, cytopenia, hyperferritinaemia, and/or CNS symptoms.

Expression of a killer cell receptor-like gene in plastic regions of the central nervous system.

A property common to the immune system and the nervous system is regulation by a highly complex and adaptable network of cellular interactions. Major histocompatibility complex (MHC) class I molecules, which are ligands of antigen-specific receptors on CD8 T cells and of inhibitory receptors on natural killer cells, have an important and surprising role in the control of activity-dependent neuronal plasticity in the central nervous system (CNS). While expression of MHC class I molecules in neurons has been reported, corresponding immune receptors have not been identified in the CNS. Here we show selective expression of a gene related to killer cell immunoglobulin-like receptor (KIR) genes in subregions of the mouse brain where synaptic plasticity and neurogenesis occur, including olfactory bulbs, rostral migratory stream and dentate gyrus of hippocampus. These results suggest new functions for KIR-like molecules in the CNS.