Reference values for peripheral blood lymphocyte subsets of healthy children in China

Identification and Functional Analysis of a de novo IKZF3 Mutation in a Pediatric Patient with Combined Immunodeficiency

AIOLOS, a vital member of the IKAROS protein family, plays a significant role in lymphocyte development and function through DNA binding and protein-protein interactions. Mutations in the IKZF3 gene, which encodes AIOLOS, lead to a rare combined immunodeficiency often linked with infections and malignancy. In this study, we evaluated a 1-year-4-month-old female patient presenting with recurrent infections, diarrhea, and failure to thrive. Laboratory investigations revealed decreased T lymphocyte and immunoglobulin levels. Through whole-exome and Sanger sequencing, we discovered a de novo mutation in IKZF3 (NM_012481; exon 5 c.571G > C, p.Gly191Arg), corresponding to the third DNA-binding zinc finger region of the encoded protein AIOLOS. Notably, the patient with the AIOLOS G191R mutation showed reduced recent thymic emigrants in naïve CD4+T cells compared to healthy counterparts of the same age, while maintaining normal levels of Th1, Th2, Th17, Treg, and Tfh cells. This mutation also resulted in decreased switched memory B cells and lower CD23 and IgM expression. In vitro studies revealed that AIOLOS G191R does not impact the expression of AIOLOS but compromises its stability, DNA binding and pericentromeric targeting. Furthermore, AIOLOS G191R demonstrated a dominant-negative effect over the wild-type protein. This case represents the first reported instance of a mutation in the third DNA-binding zinc finger region of AIOLOS highlighting its pivotal role in immune cell functionality.

Atypical familial hemophagocytic lymphohistiocytosis type 3 in children: A report of cases and literature review

BACKGROUND

Familial hemophagocytic lymphohistiocytosis type 3 (FHL3) is caused by UNC13D variants. The clinical manifestations of FHL3 are highly diverse and complex. Some patients exhibit atypical or incomplete phenotypes, making accurate diagnosis difficult. Our study aimed to broaden the understanding of the atypical FHL3 clinical spectrum.

METHODS

In our study, we analyzed in detail the clinical features of four Chinese patients with UNC13D variants. Additionally, we conducted a comprehensive review of the existing literature on previously reported atypical manifestations and summarized the findings.

RESULTS

Two of our patients presented with muscle involvement, while the other two had hematological involvement; none of them met the diagnostic criteria for hemophagocytic lymphohistiocytosis (HLH). However, protein expression and functional analysis ultimately confirmed diagnostic criteria for FHL3 in all patients. From the literature we reviewed, many atypical FHL3 patients had neurological involvement, especially isolated neurological manifestations. At the same time, arthritis and hypogammaglobulinemia were also prone to occur.

CONCLUSION

Our study highlights that the expression of the Munc13-4 protein may not fully indicate the pathogenicity of UNC13D variants, whereas CD107a analysis could be more sensitive for disease diagnosis. These findings contribute to a broader understanding of the FHL3 clinical spectrum and may offer new insights into the underlying pathogenesis of UNC13D variants. It is crucial to prioritize the timely and accurate diagnosis of atypical patients, as they may often be overlooked among individuals with rheumatic or hematological diseases.

Impact of different genetic mutations on granulocyte development and G-CSF responsiveness in congenital neutropenia

ABSTRACT

Congenital neutropenia (CN) is a genetic disorder characterized by persistent or intermittent low peripheral neutrophil counts, thus increasing susceptibility to bacterial and fungal infections. Various forms of CN, caused by distinct genetic mutations, exhibit differential responses to granulocyte colony-stimulating factor (G-CSF) therapy, with the underlying mechanisms not fully understood. This study presents an in-depth comparative analysis of clinical and immunological features in 5 CN patient groups (severe congenital neutropenia [SCN]1, SCN3, cyclic neutropenia [CyN], warts, hypogammaglobulinaemia, infections and myelokathexis [WHIM], and Shwachman-Bodian-Diamond Syndrome [SBDS]) associated with mutations in ELANE, HAX1, CXCR4, and SBDS genes. Our analysis led to the identification of 11 novel mutations in ELANE and 1 each in HAX1, CXCR4, and G6PC3 genes. Investigating bone marrow (BM) granulopoiesis and blood absolute neutrophil count after G-CSF treatment, we found that SCN1 and SCN3 presented with severe early-stage disruption between the promyelocyte and myelocyte, leading to a poor response to G-CSF. In contrast, CyN, affected at the late polymorphonuclear stage of neutrophil development, showed a strong G-CSF response. WHIM, displaying normal neutrophil development, responded robustly to G-CSF, whereas SBDS, with moderate disruption from the early myeloblast stage, exhibited a moderate response. Notably, SCN1 uniquely impeded neutrophil development, whereas SCN3, CyN, WHIM, and SBDS also affected eosinophils and basophils. In addition, SCN1, SCN3, and CyN presented with elevated serum immunoglobulins, increased BM plasma cells, and higher A Proliferation-Inducing Ligand levels. Our study reveals a strong correlation between the stage and severity of granulocyte development disruption and the efficacy of G-CSF therapy.

Inborn errors of immunity and its clinical significance in children with lymphoma in China: a single-center study

OBJECTIVE

To investigate the incidence, clinical and genetic characteristics of pediatric lymphoma patients of China with inborn errors of immunity (IEI)-related gene mutations, which have not been fully studied.

METHOD

From Jan. 2020 to Mar. 2023, IEI-related genetic mutations were retrospectively explored in 108 children with lymphomas admitted to Beijing Children's Hospital by NGS. Genetic rule and clinical characteristics as well as treatment outcomes were compared between patients with or without IEI-related gene mutations.

RESULTS

A total of 17 patients (15.7 %) harbored IEI-associated mutations, including 4 cases with X-linked lymphoproliferative syndrome (XLP), 3 cases had mutations in tumor necrosis factor receptor superfamily 13B (TNFRSF13B), 2 cases with Activated p110 syndrome (APDS). Patients with IEI all had alteration of immunocompetence with decreased levels of immunoglobulin and lymphocyte subsets. Recurrent infection existed in 41.2 % of patients. The 18-month event-free survival (EFS) and the overall response rate (ORR) of patients with IEI are significantly lower than those without IEI (33.86% vs. 73.26 %, p = 0.011; 52.94% vs. 87.91 %, p = 0.002, respectively). In addition, patients with IEI had a higher progression disease (PD) rate of 23.5 % than those without IEI of 4.4 % (p = 0.006).

CONCLUSION

The present study demonstrated that IEI-associated lymphomas were much more common than originally appreciated in pediatric lymphomas, and those were insensitive to treatment and more likely to progress or relapse. The genomic analysis and a thorough review of the medical history of IEI can be used to distinguish them from pediatric lymphomas without IEI, which are beneficial for the early diagnosis and direct intervention.

The advances of E2A-PBX1 fusion in B-cell acute lymphoblastic Leukaemia

The E2A-PBX1 gene fusion is a common translocation in B-cell acute lymphoblastic leukaemia. Patients harbouring the E2A-PBX1 fusion gene typically exhibit an intermediate prognosis. Furthermore, minimal residual disease has unsatisfactory prognostic value in E2A-PBX1 B-cell acute lymphoblastic leukaemia. However, the mechanism of E2A-PBX1 in the occurrence and progression of B-cell acute lymphoblastic leukaemia is not well understood. Here, we mainly review the roles of E2A and PBX1 in the differentiation and development of B lymphocytes, the mechanism of E2A-PBX1 gene fusion in B-cell acute lymphoblastic leukaemia, and the potential therapeutic approaches.

Fading SARS-CoV-2 humoral VOC cross-reactivity and sustained cellular immunity in convalescent children and adolescents

Cross-reactive cellular and humoral immunity can substantially contribute to antiviral defense against SARS-CoV-2 variants of concern (VOC). While the adult SARS-CoV-2 cellular and humoral immunity and its cross-recognition potential against VOC is broadly analyzed, similar data regarding the pediatric population are missing. In this study, we perform an analysis of the humoral and cellular SARS-CoV-2 response immune of 32 convalescent COVID-19 children (children), 27 convalescent vaccinated adults(C + V+) and 7 unvaccinated convalescent adults (C + V-). Similarly to adults, a significant reduction of cross-reactive neutralizing capacity against delta and omicron VOC was observed 6 months after SARS-CoV-2 infection. While SAR-CoV-2 neutralizing capacity was comparable among children and C + V- against all VOC, children demonstrated as expected an inferior humoral response when compared to C + V+. Nevertheless, children generated SARS-CoV-2 reactive T cells with broad cross-recognition potential. When compared to V + C+, children presented even comparable frequencies of WT-reactive CD4 + and CD8 + T cells with high avidity and functionality. Taking into consideration the limitations of study - unknown disease onset for 53% of the asymptomatic pediatric subjects, serological detection of SARS-CoV-2 infection-, our results suggest that following SARS-CoV-2 infection children generate a humoral SARS-CoV-2 response with neutralizing potential comparable to unvaccinated COVID-19 convalescent adults as well a sustained SARS-CoV-2 cellular response cross-reactive to VOC.

The genetic and clinical characteristics and effects of Canakinumab on cryopyrin-associated periodic syndrome: a large pediatric cohort study from China

Cryopyrin-associated periodic syndrome (CAPS) comprises a group of disorders characterized by recurrent bouts of systemic inflammation related to overactivation of inflammasome. So far, neither large cases of the correlation between genotype and phenotype nor treatment strategies have been clearly stated in China. Here, we studied the clinical and genetic characteristics and their correlation from 30 CAPS patients in China. We identified the pathogenesis for novel mutations by activating NLRP3 inflammasome for peripheral cells with ATP plus LPS, compared characteristics with other case series, and analyzed treatment outcomes of these patients. The patients harbored 19 substitutions in NLRP3, and 8 of them were novel mutations. Among these novel mutations, percentages of severe musculoskeletal, ophthalmologic, and neurological symptoms were higher compared with other case serials. The correlation of phenotypes and their variants seemed different in our cases, such as T350M, S333G/I/R, and F311V (somatic mosaicism). Ten patients received Canakinumab treatment, which proved effective at alleviating musculoskeletal, neurological, auditory, visual manifestations, fever, and rash for 10-20 months follow-up. Patients treated with prednisolone or prednisolone plus thalidomide or methotrexate, tocilizumab, TNF inhibiting agents, and sirolimus achieved only partial remission. Importantly, we firstly identified somatic mosaicism mutation of F311V, which was severe. Our study extended the spectrum of genotype and phenotype and characteristics of their correlations and provided detailed responses to different treatment strategies. These data provide guidance for future diagnosis and management for CAPS.

B cell abnormalities and autoantibody production in patients with partial RAG deficiency

Mutations in the recombination activating gene 1 (RAG1) and RAG2 in humans are associated with a broad spectrum of clinical phenotypes, from severe combined immunodeficiency to immune dysregulation. Partial (hypomorphic) RAG deficiency (pRD) in particular, frequently leads to hyperinflammation and autoimmunity, with several underlying intrinsic and extrinsic mechanisms causing a break in tolerance centrally and peripherally during T and B cell development. However, the relative contributions of these processes to immune dysregulation remain unclear. In this review, we specifically focus on the recently described tolerance break and B cell abnormalities, as well as consequent molecular and cellular mechanisms of autoantibody production in patients with pRD.

A Multicenter Cohort Study of Immune Dysregulation Disorders Caused by ELF4 Variants in China

Patients with DEX (deficiency in ELF4, X-linked) were recently reported by our team and others, and cases are very limited worldwide. Our knowledge of this new disease is currently preliminary. In this study, we described 5 more cases presenting mainly with oral ulcer, inflammatory bowel disease-like symptoms, fever of unknown origin, anemia, or systemic lupus erythematosus. Whole exome sequencing identified potential pathogenic ELF4 variants in all cases. The pathogenicity of these variants was confirmed by the detection of ELF4 expression in peripheral blood mononuclear cells from patients and utilizing a simple IFN-b luciferase reporter assay, as previously reported. Our findings significantly contribute to the current understanding of DEX.

Differential analysis of immune reconstitution after allogeneic hematopoietic stem cell transplantation in children with Wiskott-Aldrich syndrome and chronic granulomatous disease

Objective

To investigate similarities and differences in immune reconstitution after allogeneic hematopoietic stem cell transplantation (allo-HSCT) in children with Wiskott-Aldrich syndrome (WAS) and chronic granulomatous disease (CGD).

Method

We retrospectively analyzed the lymphocyte subpopulations and the serum level of various immune-related protein or peptide on Days 15, 30, 100, 180 and 360 post-transplantation in 70 children with WAS and 48 children with CGD who underwent allo-HSCT at the Transplantation Center of the Department of Hematology-Oncology, Children's Hospital of Chongqing Medical University from January 2007 to December 2020, and we analyzed the differences in the immune reconstitution process between the two groups.

Results

① The WAS group had higher lymphocyte subpopulation counts than the CGD group. ② Among children aged 1-3 years who underwent transplantation, the WAS group had higher lymphocyte subpopulation counts than the CGD group. ③ Further comparisons were performed between children with non-umbilical cord blood transplantation (non-UCBT) and children with umbilical cord blood transplantation (UCBT) in the WAS group. On Day 15 and 30 post-transplantation, the non-UCBT group had higher B-cell counts than the UCBT group. On the remaining time points post-transplantation, the UCBT group had higher lymphocyte subpopulation counts than the non-UCBT group. ④ Comparisons were performed between children with non-UCBT in the WAS group and in the CGD group, the lymphocyte subpopulation counts were higher in the WAS group compared to the CGD group. ⑤ On Day 100 post-transplantation, the CGD group had higher C3 levels than the WAS group. On Day 360 post-transplantation, the CGD group had higher IgA and C4 levels than the WAS group.

Conclusion

① The rate of immunity recovery was faster in children within the WAS group compared to those children within the CGD group, which may be attributed to the difference of percentage undergoing UCBT and primary diseases. ② In the WAS group, the non-UCBT group had higher B-cell counts than the UCBT group at Day 15 and 30 post-transplantation, however, the UCBT group had higher B-cell counts than the non-UCBT group at Day 100 and 180 post-transplantation, suggesting that cord blood has strong B-cell reconstitution potentiality after transplantation.

Immunological assessment of a patient with Omenn syndrome resulting from compound heterozygous mutations in the RAG1 gene

The recombination activating gene 1 (RAG1) is essential for V(D)J recombination during T- and B-cell development. In this study, we presented a case study of a 41-day-old female infant who exhibited symptoms of generalized erythroderma, lymphadenopathy, hepatosplenomegaly, and recurrent infections including suppurative meningitis and septicemia. The patient showed a T⁺B^-NK⁺ immunophenotype. We observed an impaired thymic output, as indicated by reduced levels of naive T cells and sjTRECs, coupled with a restricted TCR repertoire. Additionally, T-cell CFSE proliferation was impaired, indicating a suboptimal T-cell response. Notably, our data further revealed that T cells were in an activated state. Genetic analysis revealed a previously reported compound heterozygous mutation (c. 1186C > T, p. R396C; c. 1210C > T, p. R404W) in the RAG1 gene. Structural analysis of RAG1 suggested that the R396C mutation might lead to the loss of hydrogen bonds with neighboring amino acids. These findings contribute to our understanding of RAG1 deficiency and may have implications for the development of novel therapies for patients with this condition.

Two patients with ZAP-70 deficiency in China present with a different genetic, immunological, and clinical phenotype

Zeta(ζ)-Chain Associated Protein Kinase 70 kDa (ZAP-70) deficiency is a rare autosomal recessive primary immunodeficiency disease. Little is known about this disease. In this study, we report two patients to extend the range of clinical phenotypes and immunophenotypes associated with ZAP-70 mutations. We describe the clinical, genetic, and immunological phenotypes of two patients with ZAP-70 deficiency in China, and the data are also compared with the literature. Case 1 presented with leaky severe combined immunodeficiency with low to the absence of CD8 + T cells, while case 2 suffered from a recurrent respiratory infection and had a past medical history of non-EBV-associated Hodgkin's lymphoma. Sequencing revealed novel compound heterozygous mutations in ZAP-70 of these patients. Case 2 is the second ZAP-70 patient presenting a normal CD8 + T cell number. These two cases have been treated with hematopoietic stem cell transplantation. Selective CD8 + T cell loss is an essential feature of the immunophenotype of ZAP-70 deficiency patients, but there are exceptions. Hematopoietic stem cell transplantation can provide excellent long-term immune function and resolution of clinical problems.

Single-cell RNA sequencing reveals the molecular features of peripheral blood immune cells in children, adults and centenarians

Peripheral blood immune cells have different molecular characteristics at different stages of the whole lifespan. Knowledge of circulating immune cell types and states from children to centenarians remains incomplete. We profiled peripheral blood mononuclear cells (PBMCs) of multiple age groups with single-cell RNA sequencing (scRNA-seq), involving the age ranges of 1-12 (G1), 20-30(G2), 30-60(G3), 60-80(G4), and >110 years (G5). The proportion and states of myeloid cells change significantly from G1 to G2. We identified a novel CD8⁺CCR7⁺GZMB⁺ cytotoxic T cell subtype specific in G1, expressing naive and cytotoxic genes, and validated by flow cytometry. CD8⁺ T cells showed significant changes in the early stage (G1 to G2), while CD4⁺ T cells changed in the late stage (G4 to G5). Moreover, the intercellular crosstalk among PBMCs in G1 is very dynamic. Susceptibility genes for a variety of autoimmune diseases (AIDs) have different cell-specific expression localization, and the expression of susceptibility genes for AIDs changes with age. Notably, the CD3⁺ undefined T cells clearly expressed susceptibility genes for multiple AIDs, especially in G3. ETS1 and FLI1, susceptibility genes associated with systemic lupus erythematosus, were differentially expressed in CD4⁺ and CD8⁺ effector cells in G1 and G3. These results provided a valuable basis for future research on the unique immune system of the whole lifespan and AIDs.

De Novo Somatic Mosaicism of CYBB Caused by Intronic LINE-1 Element Insertion Resulting in Chronic Granulomatous Disease

Chronic granulomatosis disease (CGD) is a rare inborn error of immunity, characterized by phagocytic respiratory outbreak dysfunction. Mutations causing CGD occur in CYBB on the X chromosome and in the autosomal genes CYBA, NCF1, NCF2, NCF4, RAC2, and CYBC1. Nevertheless, some patients are clinically diagnosed with CGD, due to abnormal respiratory outbursts, while the pathogenic gene mutation is unidentified. Here, we report a patient with CGD who first presented with Bacillus Calmette-Guérin disease and had recurrent pneumonia. He was diagnosed with CGD by nitro blue tetrazolium and respiratory burst tests. Detailed assessment of neutrophil activity revealed that patient neutrophils were almost entirely nonfunctional. Sanger sequencing detected a 6-kb insertion of a LINE-1 transposable element in the third intron of CYBB, leading to abnormal splicing and pseudoexon insertion, as well as introduction of a premature termination codon, resulting in predicted protein truncation. Clonal analysis demonstrated that the patient had somatic mosaicism, and the phagocytes were almost all variant CYBB, while the mosaicism rate of PBMC was about 65%. Finally, deep RNA sequencing and gp91^phox expression analysis confirmed the pathogenicity of the mutation. In conclusion, we demonstrate that insertion of a LINE-1 transposon in a CYBB intron was responsible for CGD in our patient. Intron LINE-1 transposon element insertion should be examined in CGD patients without any known disease-causing gene mutation, in addition to identification of new genes.

A Novel RAC2 Mutation Causing Combined Immunodeficiency

PURPOSE

Ras-related C3 botulinum toxin substrate 2 (RAC2) acts as a molecular switch and has crucial roles in cell signaling and actin dynamics. A broad spectrum of genetic RAC2 mutations can cause various types of primary immunodeficiency, with complete penetrance. Here, we report a novel heterozygous missense mutation in RAC2 with incomplete penetrance, and the associated phenotypes, in a Chinese family.

METHODS

Immunological phenotype was detected by flow cytometry. T cell receptor excision circles (TRECs) and K-deleting recombination excision circles (KRECs) were assessed by real-time quantitative PCR. Gene mutations were detected by whole-exome sequencing (WES) and confirmed by Sanger sequencing.

RESULTS

The proband was an 11-year-old girl who presented with recurrent respiratory infections, bronchiectasis, persistent Epstein-Barr virus viremia, infectious mononucleosis, encephalitis, and cutaneous human papillomavirus infections. Laboratory analyses revealed increased serum IgG and decreased IgM levels, reduced naïve CD4⁺ and CD8⁺ T cells, an inverted CD4⁺/CD8⁺ ratio, and low TREC and KREC numbers. The mutation resulted in increased production of reactive oxygen species, while impaired actin polarization in neutrophils; diminished proliferative responses, increased cytokine production and a dysregulated phenotype in T lymphocytes; as well as accelerated apoptosis and hyperactivity of AKT in HL-60 human leukemia cells. WES identified a c.44G > A mutation in RAC2 resulting in a p.G15D substitution. Despite sharing the same mutation as the proband, her father suffered from recurrent respiratory infections and bronchiectasis, and had similar immunological defects, whereas her sister was apparently healthy, other than cutaneous human papillomavirus infections, and only mild immunological defects were detected preliminarily.

CONCLUSIONS

Our findings broaden the clinical and genetic spectra of RAC2 mutations and underline the importance of RAC2 gain-of-function mutations with complete or incomplete penetrance.

Talaromyces marneffei Infections in 8 Chinese Children with Inborn Errors of Immunity

Purpose

Talaromyces marneffei (TM) is an opportunistic fungus leading to multi-organ damages and poor prognosis in immunocompromised individuals. TM infections in children are rare and our knowledge to TM infection is insufficient. To investigate the clinical characteristics of TM-infected children and to explore the underlying mechanisms for host against TM, we analysed TM-infected patients diagnosed in our hospital.

Methods

Eight patients with TM infections have been identified in Shenzhen Children’s Hospital during 2017–2021. Clinical data were collected from medical records. Immunological features were evaluated by flow cytometry. Literatures were also reviewed to summarize the reported inborn errors of immunity (IEIs) with TM infections.

Results

All 8 children were HIV-negative. The most common symptom of TM infections was fever (8/8), followed by weight loss (7/8), pneumonia (7/8), hepatomegaly (7/8), splenomegaly (6/8), anemia (6/8), lymphadenopathy (5/8), thrombocytopenia (3/8), diarrhea (3/8), rashes or skin lesions (3/8), and osteolytic lesions (1/8). Five children died during the follow-ups. CD3+ T cells were decreased in 6 patients. Eight patients had reduced natural killer cells. All patients went gene sequencing and were finally diagnosed as IEIs, including STAT1 gain-of-function, IL-2 receptor common gamma chain deficiency, adenosine deaminase deficiency, CD40 ligand deficiency, and STAT3 deficiency. Another 4 types of IEIs (CARD9, IFN-γ receptor 1, RelB, and NFKB2 deficiency), have been reported with TM infections based on literature review.

Conclusion

TM infections resulted in systemic injuries and high mortality. The spectrum of IEIs underlying TM infections indicated that T cell-mediated immunity, IFN-γ, IL-17 signalings and NF-κB pathways were important for host responses against TM infection. In reverse, for HIV-negative children without other secondary immunodeficiencies, IEIs should be considered in TM-infected children.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11046-022-00659-0.

Identification of two novel variants of the BCL11B gene in two Chinese pedigrees associated with neurodevelopmental disorders

Objective

According to a recent report, the mutation of transcription factor gene BCL11B is associated with the development of neurodevelopmental disorders and immune deficiency. By analyzing both clinical features and genetic variations, this study aims to reveal the genetic etiology of four patients with neurodevelopmental disorders from two unrelated Chinese pedigrees.

Methods

From the 4 cases, the clinical data were collected. The potential pathogenic gene variations were analyzed by means of based-trio whole exome sequencing (Trio-WES) and then validated through Sanger sequencing in their respective pedigrees. Furthermore, both the in vitro minigene assay and the NMD assay were performed to evaluate the impact of splicing and frameshift variants.

Results

The 4 patients displayed mild-to-severe intellectual developmental disorder, which was accompanied by speech delay, dysmorphic facies, and serious caries. In addition, the extended phenotype of developmental regression was observed in the proband from Family 1, which has been unreported previously. Molecular analysis was conducted to identify two novel heterozygous variants in the BCL11B gene: a maternal splicing variant c.427 + 1G > A in Family 1 and a de novo frameshift variant c.2461_2462insGAGCCACACCGGCG (p.Glu821Glyfs*28) in Family 2. As revealed by the in vitro minigene assay, the c.427 + 1G > A variant activated a new cryptic splice site. As confirmed by an overexpression assay, there was no significant difference in the level of mRNA and protein expression between the mutate-BCL11B (p.Glu821Glyfs*28) and the wild type. It confirms that p.Glu821Glyfs*28 variant could be an NMD escaping variant.

Conclusion

The extended phenotype of BCL11B-related disorders is reported in this study to reveal the clinical and genetic heterogeneity of the disease. The study starts by identifying a splicing variant and a novel frameshift variant of the BCL11B gene, thus confirming its aberrant translation. The findings of this study expand the mutation spectrum of the genetic BCL11B gene, which not only improves the understanding of the associated neurodevelopmental disorders from a clinical perspective but also provides guidance on diagnosis and genetic counseling for patients.

Rapid diagnosis of Talaromyces marneffei infection by metagenomic next-generation sequencing technology in a Chinese cohort of inborn errors of immunity

Talaromyces marneffei (T. marneffei) is an opportunistic pathogen. Patients with inborn errors of immunity (IEI) have been increasingly diagnosed with T. marneffei in recent years. The disseminated infection of T. marneffei can be life-threatening without timely and effective antifungal therapy. Rapid and accurate pathogenic microbiological diagnosis is particularly critical for these patients. A total of 505 patients with IEI were admitted to our hospital between January 2019 and June 2022, among whom T. marneffei was detected in 6 patients by metagenomic next-generation sequencing (mNGS), and their clinical and immunological characteristics were summarized. We performed a systematic literature review on T. marneffei infections with published immunodeficiency-related gene mutations. All patients in our cohort were confirmed to have genetic mutations in IL12RB1, IFNGR1, STAT1, STAT3, and CD40LG. T. marneffei was detected in both the blood and lymph nodes of P1 with IL12RB1 mutations, and the clinical manifestations were serious and included recurrent fever, weight loss, severe anemia, splenomegaly and lymphadenopathy, all requiring long-term antifungal therapy. These six patients received antifungal treatment, which relieved symptoms and improved imaging findings. Five patients survived, while one patient died of sepsis after hematopoietic stem cell transplantation. The application of mNGS methods for pathogen detection in IEI patients and comparison with traditional diagnosis methods were investigated. Traditional diagnostic methods and mNGS tests were performed simultaneously in 232 patients with IEI. Compared to the traditional methods, the sensitivity and specificity of mNGS in diagnosing T. marneffei infection were 100% and 98.7%, respectively. The reporting time for T. marneffei detection was approximately 26 hours by mNGS, 3-14 days by culture, and 6-11 days by histopathology. T. marneffei infection was first reported in IEI patients with IL12RB1 gene mutation, which expanded the IEI lineage susceptible to T. marneffei. For IEI patients with T. marneffei infection, we highlight the application of mNGS in pathogenic detection. mNGS is recommended as a front-line diagnostic test for rapidly identifying pathogens in complex and severe infections.

Clinical and immunological characteristics of five patients with immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome in China–expanding the atypical phenotypes

Background

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is a rare disorder of the immune regulatory system caused by forkhead box P3 (FOXP3) mutations. Abnormal numbers or functions of regulatory T (Treg) cells account for the various autoimmune symptoms. We aimed to explore the molecular genetics and phenotypic spectra of patients with atypical IPEX syndrome in China.

Methods

We analyzed the molecular, clinical and immune phenotype characteristics of five Chinese patients with FOXP3 mutations.

Results

We summarized the molecular and phenotypic features of five patients with FOXP3 mutations, including two novel mutations. Four of the five patients displayed atypical phenotypes, and one developed immune-related peripheral neuropathy. Three of the five patients showed normal frequencies of Treg cells, but the proportions of subsets of Treg cells, CD4⁺ T cells and B cells were out of balance.

Conclusions

Our report broadens the understanding of the clinical features of atypical IPEX syndrome. Our detailed analyses of the immunological characteristics of these patients enhance the understanding of the possible mechanisms underlying the clinical manifestations.

The Predictive Value of Changes in the Absolute Counts of Peripheral Lymphocyte Subsets for Progression and Prognosis in Breast Cancer Patients

Background

As the number and proportion of lymphocyte subsets are an important indicator of the immune function, an in depth understanding of the immune function of patients with malignant tumor has important clinical values for the treatment, prognosis, and evaluation of the disease. This retrospective study was to evaluate the clinical value of the absolute counts of lymphocyte subsets as potential blood biomarkers for progression and prognosis in breast cancer patients.

Methods

A total of 237 BC patients and 55 age-matched female normal healthy donors were included in this study. Flow cytometry was used to determine the absolute counts and the percentages of CD3⁺, CD4⁺, CD8⁺, B, and NK cells. The receiver operating characteristic curve (ROC) was used to evaluate the accuracy of absolute count of lymphocyte subsets in the curative efficacy assessment. The clinicopathological parameters influencing the disease progression were determined by Cox proportional hazards regression. Progression-free survival (PFS) was estimated using the Kaplan–Meier method with the log-rank test. Results: Compared with the healthy donors, the absolute counts of lymphocyte subsets in patients decreased significantly. ROC analysis showed that the area under the curve of the CD4⁺ absolute count was 90% (95% confidence interval 0.859–0.940), and the sensitivity and specificity were 80.9% and 85.3%, respectively. The analysis of Cox regression showed that the cutoff value of the CD4⁺ absolute count ≥451 cells/μL might be a favorable prognostic factor. Multivariate analysis of prognostic factors of PFS showed that the CD4⁺ and CD8⁺ absolute count were independent factors for predicting PFS.

Conclusions

The remarkably impaired absolute counts of the CD3⁺, CD4⁺, CD8⁺, B, and NK cells in patients with breast cancer can be used as potential susceptible biomarkers to evaluate the patient's immune status. The higher level of CD4⁺ and CD8⁺ absolute counts probably contributed to the longer PFS and favorable outcome of BC patients.

Establishing Reference Values for Peripheral Blood Lymphocyte Subsets of Healthy Children in China Using a Single Platform

Lymphocyte subsets significantly change during childhood; thus, age-matched reference values derived from healthy children are crucial. We established reference values for lymphocyte subsets, including T cells (CD3+), CD4 T cells (CD3 + CD4+), CD8 T cells (CD3 + CD8+), double negative T (DNT) cells (CD3 + CD4-CD8-), B cells (CD3-CD19+), NK cells (CD3-CD56+), and NKT-like cells (CD3 + CD56+) in the peripheral blood of 813 healthy children. We used the method of the international standard document (Clinical Laboratory Standard Institute C28-A3) to establish reference intervals with a single platform. First, we used the Skewness and Kurtosis test to analyze the normality of the data. The nonnormally distributed data was transformed into approximately normal distribution by the Box-Cox transformation. Second, we used the Tukey's method to eliminate outliers. Further, all the subjects were grouped into subgroups according to sex (male and female) and age (0–1 month, 2–12 months, 1–3 years, 4–6 years, and 7–18 years). We used the standard normal deviation test (Z-test) to evaluate whether age and sex were possible grouping factors. The analyses indicated age to be an important factor associated with changes in lymphocyte subsets. The absolute number of lymphocyte subsets and total number of lymphocytes, T cells, CD4 T cells, CD8 T cells, and B cells gradually increase from birth to 12 months and then gradually decrease with age. Furthermore, CD4 T cells and the ratio of CD4⁺/CD8⁺ gradually decrease with age. In contrast, CD8 T and DNT cells gradually increase with age. The percentage and number of NK and NKT-like cells gradually increase with age and remain stable between 1 and 18 years of age. In conclusion, the age-related reference intervals established in healthy children in this study can aid in monitoring and assessing the changes in immune levels in diseased conditions.

Chromosomal abnormalities related to fever of unknown origin in a Chinese pediatric cohort and literature review

BACKGROUND

Fever of unknown origin (FUO) has been difficult to diagnose in pediatric clinical practice. With the gradual change in the disease spectrum, genetic factors have received increasing attention. Limited studies have shown an association between FUO and chromosomal abnormalities. In this study, we investigated the clinical and genetic characteristics of patients with FUO presenting with chromosomal abnormalities in a Chinese pediatric cohort.

RESULTS

Chromosomal abnormalities were detected in 5.5% (8/145) of the patients with FUO. Six patients with inflammatory fever presented with pharyngitis/amygdalitis (4/6), oral aphthous ulcer (2/6), digestive symptoms (3/6), developmental delay (4/6) and elevated C-reactive protein levels (6/6) during fever. These patients were often considered to have systemic inflammatory diseases, such as Behcet's disease or systemic juvenile idiopathic arthritis. Trisomy 8, 7q11.23 dup, 3p26.3-p26.1 del/17q12 dup, 22q11.21 del, and 6q23.3-q24.1 del were identified in patients with inflammatory fever. The TNFAIP3 gene was included in the 6q23.3-q24.1 deletion fragment. Two patients with central fever were characterized by facial anomalies, developmental delay, seizures and no response to antipyretic drugs and were identified as carrying the de novo 18q22.3-q23 del. By performing a literature review, an additional 19 patients who had FUO and chromosomal abnormalities were identified. Trisomy 8, 6q23.2-q24.3 del and 18q22.3-q23 del were reported to present as fever, similar to the findings of our study.

CONCLUSIONS

We emphasized the important role of detecting chromosomal abnormalities in patients with FUO, especially in patients with systemic inflammatory manifestations or developmental delay. Identifying chromosomal abnormalities may change the diagnosis and management of patients with FUO.

Recovering or Persisting: The Immunopathological Features of SARS-CoV-2 Infection in Children

Background. The profile of cellular immunological responses of children across the spectrum of COVID-19, ranging from acute SARS-CoV-2 infection to full recovery or Long COVID, has not yet been fully investigated. Methods. We examined and compared cytokines in sera and cell subsets in peripheral blood mononuclear cells (B and regulatory T lymphocytes) collected from four distinct groups of children, distributed as follows: younger than 18 years of age with either acute SARS-CoV-2 infection (n = 49); fully recovered from COVID-19 (n = 32); with persistent symptoms (Long COVID, n = 51); and healthy controls (n = 9). Results. In the later stages after SARS-CoV-2 infection, the cohorts of children, both with recovered and persistent symptoms, showed skewed T and B subsets, with remarkable differences when compared with children at the onset of the infection and with controls. The frequencies of IgD+CD27− naïve B cells, IgD+IgM+ and CD27−IgM+CD38dim B cells were higher in children with recent infection than in those with an older history of disease (p < 0.0001 for all); similarly, the total and natural Tregs compartments were more represented in children at onset when compared with Long COVID (p < 0.0001 and p = 0.0005, respectively). Despite the heterogeneity, partially due to age, sex and infection incidence, the susceptibility of certain children to develop persistent symptoms after infection appeared to be associated with the imbalance of the adaptive immune response. Following up and comparing recovered versus Long COVID patients, we analyzed the role of circulating naïve and switched B and regulatory T lymphocytes in counteracting the evolution of the symptomatology emerged, finding an interesting correlation between the amount and ability to reconstitute the natural Tregs component with the persistence of symptoms (linear regression, p = 0.0026). Conclusions. In this study, we suggest that children affected by Long COVID may have a compromised ability to switch from the innate to the adaptive immune response, as supported by our data showing a contraction of naïve and switched B cell compartment and an unstable balance of regulatory T lymphocytes occurring in these children. However, further prospective immunological studies are needed to better clarify which factors (epigenetic, diet, environment, etc.) are involved in the impairment of the immunological mechanisms in the Long COVID patients.

Novel CD81 Mutations in a Chinese Patient Led to IgA Nephropathy and Impaired BCR Signaling

PURPOSE

CD81 deficiency is an extremely rare primary immunodeficiency disease characterized by severe and recurrent infections, IgA-related nephropathy, and profound hypogammaglobulinemia. Only one patient has been reported so far, and the pathogenesis remains unclear. Here, we identified a new case of CD81 deficiency and described its pathogenesis.

METHODS

We analyzed the clinical, genetic, and immunological features of the patient with CD81 deficiency, and explored the pathogenesis of her antibody deficiencies.

RESULTS

The major manifestation of this patient was unexpectedly not recurrent infections but IgA nephropathy with aberrant serum galactose-deficient IgA1. Whole-exome sequencing revealed novel biallelic mutations in CD81 gene that abolished the surface expression of CD81. B cells from the patient lack membrane CD19 and showed reduced switched memory B cells and transitional B cells. Decreased expression of key molecules pY and pBTK in BCR signaling were demonstrated by confocal microscopy. RNA sequencing revealed that genes associated with BCR signaling and immunoglobulins were downregulated in CD81-deficient B cells. In addition, the patient showed increased frequency of T follicular helper cells that biased to Th1-like subsets.

CONCLUSION

We reported the second patient with CD81 deficiency in the world and illustrated aberrant BCR signaling in the patient, therefore helping to unravel the mechanism of antibody deficiency in CD81-deficient patients.

Cellular Mechanisms Underlying B Cell Abnormalities in Patients With Gain-of-Function Mutations in the PIK3CD Gene

Background

Activated phosphoinositide 3 kinase (PI3K) -delta syndrome (APDS) is an inborn error of immunity with variable clinical phenotype of immunodeficiency and immune dysregulation and caused by gain-of-function mutations in PIK3CD. The hallmark of immune phenotype is increased proportions of transitional B cells and plasmablasts (PB), progressive B cell loss, and elevated levels of serum IgM.

Objective

To explore unique B cell subsets and the pathomechanisms driving B cell dysregulation beyond the transitional B cell stage in APDS.

Methods

Clinical and immunological data was collected from 24 patients with APDS. In five cases, we performed an in-depth analysis of B cell phenotypes and cultured purified naïve B cells to evaluate their survival, activation, Ig gene class switch recombination (CSR), PB differentiation and antibody secretion. We also analyzed PB differentiation capacity of sorted CD27^-IgD^- double-negative B (DNB) cells.

Results

The patients had increased B cell sizes and higher proportions of IgM⁺ DNB cells than healthy controls (HC). Their naïve B cells exhibited increased death, impaired CSR but relatively normal PB differentiation. Upon stimulation, patient’s DNB cells secreted a similar level of IgG but a higher level of IgM than DNB cells from HC. Targeted therapy of PI3K inhibition partially restored B cell phenotypes.

Conclusions

The present study suggests additional mechanistic insight into B cell pathology of APDS: (1) decreased peripheral B cell numbers may be due to the increased death of naïve B cells; (2) larger B cell sizes and expanded DNB population suggest enhanced activation and differentiation of naïve B cells into DNB cells; (3) the impaired CSR yet normal PB differentiation can predominantly generate IgM-secreting cells, resulting in elevated IgM levels.

Normal B cell ranges in infants: A systematic review and meta-analysis

BACKGROUND

During the first year of life, B cell level is a valuable indicator of whether external factors, such as exposure to B cell depleting therapies, have an adverse impact on immune system development. However, there are no standard reference ranges of B cell levels in healthy infants by age.

OBJECTIVE

To estimate the normal range of B cell levels in infants, by age, during the first year of life, by pooling data from published studies.

METHODS

Studies reporting B cell levels measured using flow cytometry and CD19 markers in healthy infants were identified via a systematic literature review. Quality and feasibility assessments determined suitability for inclusion in meta-analyses by age group and/or continuous age. Means and normal ranges (2.5th-97.5th percentile) were estimated for absolute and percentage B cell levels. Sensitivity analyses assessed the impact of various assumptions.

RESULTS

Of 37 relevant studies identified, 28 were included in at least 1 meta-analysis. Means and normal ranges of B cell levels were found to be 707 (123-2324) cells/μL in cord blood, 508 (132-1369) cells/μL at age 0-1 month, 1493 (416-3877) cells/μL at age 1-6 months and 1474 (416-3805) cells/μL at age >6 months. The continuous age model showed that B cell levels peaked at week 26. Trends were similar for the percentage B cell estimates and in sensitivity analyses.

CONCLUSION

These meta-analyses provide the first normal reference ranges for B cell levels in infants, by week of age, during the first year of life.

Immunopathology of SARS-CoV-2 Infection: A Focus on T Regulatory and B Cell Responses in Children Compared with Adults

While the clinical impact of COVID-19 on adults has been massive, the majority of children develop pauci-symptomatic or even asymptomatic infection and only a minority of the latter develop a fatal outcome. The reasons of such differences are not yet established. We examined cytokines in sera and Th and B cell subpopulations in peripheral blood mononuclear cells (PBMC) from 40 children (<18 years old), evaluating the impact of COVID-19 infection during the pandemic’s first waves. We correlated our results with clinical symptoms and compared them to samples obtained from 16 infected adults and 7 healthy controls. While IL6 levels were lower in SARS-CoV-2+ children as compared to adult patients, the expression of other pro-inflammatory cytokines such as IFNγ and TNFα directly correlated with early age infection and symptoms. Th and B cell subsets were modified during pediatric infection differently with respect to adult patients and controls and within the pediatric group based on age. Low levels of IgD− CD27+ memory B cells correlated with absent/mild symptoms. On the contrary, high levels of FoxP3+/CD25high T-Regs associated with a moderate−severe clinical course in the childhood. These T and B cells subsets did not associate with severity in infected adults, with children showing a predominant expansion of immature B lymphocytes and natural regulatory T cells. This study shows differences in immunopathology of SARS-CoV-2 infection in children compared with adults. Moreover, these data could provide information that can drive vaccination endpoints for children.

Characteristics and Treatment Outcomes of Pediatric Langerhans Cell Histiocytosis with Thymic Involvement

OBJECTIVE

To evaluate the characteristics and treatment outcomes of patients with pediatric Langerhans cell histiocytosis (LCH) with thymic involvement.

STUDY DESIGN

We retrospectively described the clinical, biological, and imaging characteristics of a series of 19 patients with pediatric LCH with thymic involvement in our center between September 2016 and December 2019. We further analyzed the treatment response and outcomes of patients treated with chemotherapy or targeted therapy.

RESULTS

Thymic involvement was found in 4.4% of a 433-consecutive pediatric LCH cohort; all LCH-thymic involvement presented with multisystem disease. Patients with thymic involvement were typically younger, harboring more lung and thyroid involvement and less bone involvement than those without thymic involvement. Most patients with thymic involvement had alteration of immunocompetence with decreased numbers of T-lymphocyte subsets and immunoglobulin G levels. Overall, 47.1% of patients demonstrated a response after 6 weeks of induction therapy, and 92.3% of the patients who did not respond to the first-line treatment had resolution of thymus after the second-line and/or targeted therapy. The progression/relapse rate showed no difference between patients who shifted to second-line therapy and those to dabrafenib (33.3% vs 25%, P = 1.000). The survival for patients with thymic involvement did not differ from those without thymic involvement. More patients treated with second-line chemotherapy had severe adverse events than those given dabrafenib (88.9% vs 0, P < .001).

CONCLUSIONS

Thymic involvement was observed rarely in LCH and had specific clinical characteristics. Chemotherapy could resolve most thymic lesions, and BRAF inhibitors might provide a promising treatment option with less toxicity for infants with BRAF-V600E mutation.

TRIAL REGISTRATION

http://www.chictr.org.cn, identifier: ChiCTR2000030457 (BCH-LCH 2014 study); ChiCTR2000032844 (dabrafenib study).

Activated Phosphoinositide 3-Kinase δ Syndrome: a Large Pediatric Cohort from a Single Center in China

PURPOSE

Activated phosphoinositide 3-kinase δ syndrome (APDS) is a primary immunodeficiency first described in 2013, which is caused by gain-of-function mutations in PIK3CD or PIK3R1, and characterized by recurrent respiratory tract infections, lymphoproliferation, herpesvirus infection, autoimmunity, and enteropathy. We sought to review the clinical phenotypes, immunological characteristics, treatment, and prognosis of APDS in a large genetically defined Chinese pediatric cohort.

METHODS

Clinical records, radiology examinations, and laboratory investigations of 40 APDS patients were reviewed. Patients were contacted via phone call to follow up their current situation.

RESULTS

Sinopulmonary infections and lymphoproliferation were the most common complications in this cohort. Three (10.3%) and five (12.5%) patients suffered localized BCG-induced granulomatous inflammation and tuberculosis infection, respectively. Twenty-seven patients (67.5%) were affected by autoimmunity, while malignancy (7.5%) was relatively rare to be seen. Most patients in our cohort took a combined treatment of anti-infection prophylaxis, immunoglobulin replacement, and immunosuppressive therapy such as glucocorticoid or rapamycin administration. Twelve patients underwent hematopoietic stem cell transplantation (HSCT) and had a satisfying prognosis.

CONCLUSION

Clinical spectrum of APDS is heterogeneous. This cohort's high incidence of localized BCG-induced granulomatous inflammation and tuberculosis indicates Mycobacterial susceptibility in APDS patients. Rapamycin is effective in improving lymphoproliferation and cytopenia. HSCT is an option for those who have severe complications and poor response to other treatments.

Loss of Function Mutation in ELF4 Causes Autoinflammatory and Immunodeficiency Disease in Human

Monogenic autoinflammatory diseases (mAIDs) are a heterogeneous group of diseases affecting primarily innate immunity, with various genetic causes. Genetic diagnosis of mAIDs can assist in the patient's management and therapy. However, a large number of sporadic and familial cases remain genetically uncharacterized. Deficiency in ELF4, X-linked (DEX) is recently identified as a novel mAID. Here, we described a pediatric patient suffering from recurrent viral and bacterial respiratory infection, refractory oral ulcer, constipation, and arthritis. Whole-exome sequencing found a hemizygous variant in ELF4 (chrX:129205133 A > G, c.691 T > C, p.W231R). Using cells from patient and point mutation mice, we showed mutant cells failed to restrict viral replication effectively and produced more pro-inflammatory cytokines. RNA-seq identified several potential critical antiviral and anti-inflammation genes with decreased expression, and ChIP-qPCR assay suggested mutant ELF4 failed to bind to the promoters of these genes. Thus, we presented the second report of DEX.

Autoimmune Cytopenias and Dysregulated Immunophenotype Act as Warning Signs of Inborn Errors of Immunity: Results From a Prospective Study

Inborn errors of immunity (IEI) are genetic disorders characterized by a wide spectrum of clinical manifestations, ranging from increased susceptibility to infections to significant immune dysregulation. Among these, primary immune regulatory disorders (PIRDs) are mainly presenting with autoimmune manifestations, and autoimmune cytopenias (AICs) can be the first clinical sign. Significantly, AICs in patients with IEI often fail to respond to first-line therapy. In pediatric patients, autoimmune cytopenias can be red flags for IEI. However, for these cases precise indicators or parameters useful to suspect and screen for a hidden congenital immune defect are lacking. Therefore, we focused on chronic/refractory AIC patients to perform an extensive clinical evaluation and multiparametric flow cytometry analysis to select patients in whom PIRD was strongly suspected as candidates for genetic analysis. Key IEI-associated alterations causative of STAT3 GOF disease, IKAROS haploinsufficiency, activated PI3Kδ syndrome (APDS), Kabuki syndrome and autoimmune lymphoproliferative syndrome (ALPS) were identified. In this scenario, a dysregulated immunophenotype acted as a potential screening tool for an early IEI diagnosis, pivotal for appropriate clinical management and for the identification of new therapeutic targets.

Assessing the safety of bioactive ingredients in infant formula that affect the immune system: recommendations from an expert panel

Bioactive ingredients for infant formula have been sought to reduce disparities in health outcomes between breastfed and formula-fed infants. Traditional food safety methodologies have limited ability to assess some bioactive ingredients. It is difficult to assess the effects of nutrition on the infant immune system because of coincident developmental adaptations to birth, establishment of the microbiome and introduction to solid foods, and perinatal environmental factors. An expert panel was convened to review information on immune system development published since the 2004 Institute of Medicine report on evaluating the safety of new infant formula ingredients and to recommend measurements that demonstrate the safety of bioactive ingredients intended for that use. Panel members participated in a 2-d virtual symposium in November 2020 and in follow-up discussions throughout early 2021. Key topics included identification of immune system endpoints from nutritional intervention studies, effects of human milk feeding and human milk substances on infant health outcomes, ontologic development of the infant immune system, and microbial influences on tolerance. The panel explored how "nonnormal" conditions such as preterm birth, allergy, and genetic disorders could help define developmental immune markers for healthy term infants. With consideration of breastfed infants as a reference, ensuring proper control groups, and attention to numerous potential confounders, the panel recommended a set of standard clinical endpoints including growth, response to vaccination, infection and other adverse effects related to inflammation, and allergy and atopic diseases. It compiled a set of candidate markers to characterize stereotypical patterns of immune system development during infancy, but absence of reference ranges, variability in methods and populations, and unreliability of individual markers to predict disease prevented the panel from including many markers as safety endpoints. The panel's findings and recommendations are applicable for industry, regulatory, and academic settings, and will inform safety assessments for immunomodulatory ingredients in foods besides infant formula.

Time course of peripheral immunophenotypes of multisystem inflammatory syndrome in children

The etiology of multiple inflammatory syndrome in children (MIS-C) remains poorly understood. As clues to elucidate the pathogenic condition, several characteristic peripheral immunophenotypes have been reported in MIS-C. However, no report has demonstrated the time course of the peripheral immunophenotype along with the clinical course in the same patient. Herein, we clarified the immunological characteristics of a Japanese patient with MIS-C. There was an initial cytokine storm followed by T-cell activation, especially of CD8⁺ T cells, with the expansion of T-cell receptor Vβ 21.3-expressing cells, which suggests superantigen-mediated T-cell activation. In addition, we also found an increase in IgG-producing cells (plasmablasts and switched memory B cells), which were accompanied by elevated serum levels of anti-SARS-CoV-2 spike antigen-specific IgG antibodies. These time course of peripheral immunophenotypes support that immunological activation against SARS-CoV-2 spike protein plays a central role in the etiology of MIS-C.

A Novel Homozygous TTC7A Missense Mutation Results in Familial Multiple Intestinal Atresia and Combined Immunodeficiency

Rare autosomal-recessive variants in tetratricopeptide repeat domain 7A (TTC7A) gene have been shown to cause intestinal and immune disorders of variable severity. Missense mutations in TTC7A gene, usually retaining most of the functional motifs, is associated with relative milder clinical presentations. In this study, we reported a patient who was suffering from severe multiple intestinal atresia (MIA) with combined immunodeficiency (CID) that led to the pyloric diaphragm, ileum atresia, colon stenosis, and multiple episodes of sepsis. In spite of several surgeries and supportive treatment, the patient died of severe sepsis and multiple organ failure at age of 3 months. The whole exome sequencing (WES) of peripheral blood samples identified a novel homozygous TTC7A missense mutation (c. 206T>C, p. L69P), inherited from his parents with consanguineous marriage. In silico analysis revealed that a hydrogen bond present between Gly65 and Leu69 in the wild-type TTC7A was disrupted by the Leu69Pro mutation. Moreover, this homozygous missense mutation led to a reduced TTC7A expression in lymphocytes and intestinal tissues, accompanied by impeded lymphocyte development. Further studies demonstrated that the PI4K-FAM126A-EFR3A pathway was impaired in colon tissues. Our data strongly support the linkage of severe MIA-CID with the missense mutation in TTC7A gene. More knowledge of the TTC7A protein functions will have important therapeutic implications for patients with MIA-CID.

Trends in TREC values according to age and gender in Chinese children and their clinical applications

T cell receptor excision circles (TRECs) are small circularized DNA elements produced during rearrangement of T cell receptor (TCR) genes. Because TRECs are fairly stable, do not replicate during mitosis, and are not diluted during division of naïve T cells (Dion et al. [1]), they are suitable for assessing the number of newly formed T cells (Ping and Denise [2]). In this study, we detected TRECs in 521 healthy Chinese children aged 0-18 years in different clinical settings. The TRECs decrease with aging and show lower levels in preterm and low birth weight (BW) babies compared to those in full-term infants, while the preterm babies can also show comparable levels of TRECs when they have a gestation age (GA)-matched BW. We found a strong correlation between TRECs and peripheral CD4 naïve T cell numbers, which was age-related. We also analyzed the TRECs in different PIDs. Since T cell defects vary in PIDs, TREC levels change inconsistently. For example, in Wiskott-Aldrich syndrome (WAS), combining the level of TREC with lymphocyte subsets can help to distinguish subtypes of disease.Conclusion: We established the reference value range for TRECs by evaluating children below 18 years old in China, which could be used to screen for PIDs during early life. What is Known: • The TREC levels are decreased with age, and there is a positive correlation between TRECs and the numbers of naïve T cells. What is New: • This is the largest study to determine TREC reference levels in healthy Chinese pediatric, we provide solid data showing a correlation between CD4 naïve T cell counts and TREC levels according to age. We point out the GA matched BW is need to be considered during the SCID newborn screening. We are the first group showed that TREC levels can help clinician distinguish different WAS phenotype.

Assessment of SARS-CoV-2 Immunity in Convalescent Children and Adolescents

Persistence of protective immunity for SARS-CoV-2 is important against reinfection. Knowledge on SARS-CoV-2 immunity in pediatric patients is currently lacking. We opted to assess the SARS-CoV-2 adaptive immunity in recovered children and adolescents, addressing the pediatrics specific immunity towards COVID-19. Two independent assays were performed to investigate humoral and cellular immunological memory in pediatric convalescent COVID-19 patients. Specifically, RBD IgG, CD4+, and CD8+ T cell responses were identified and quantified in recovered children and adolescents. SARS-CoV-2-specific RBD IgG detected in recovered patients had a half-life of 121.6 days and estimated duration of 7.9 months compared with baseline levels in controls. The specific T cell response was shown to be independent of days after diagnosis. Both CD4+ and CD8+ T cells showed robust responses not only to spike (S) peptides (a main target of vaccine platforms) but were also similarly activated when stimulated by membrane (M) and nuclear (N) peptides. Importantly, we found the differences in the adaptive responses were correlated with the age of the recovered patients. The CD4+ T cell response to SARS-CoV-2 S peptide in children aged <12 years correlated with higher SARS-CoV-2 RBD IgG levels, suggesting the importance of a T cell-dependent humoral response in younger children under 12 years. Both cellular and humoral immunity against SARS-CoV-2 infections can be induced in pediatric patients. Our important findings provide fundamental knowledge on the immune memory responses to SARS-CoV-2 in recovered pediatric patients.

RNA-Binding Protein Expression Alters Upon Differentiation of Human B Cells and T Cells

B cells and T cells are key players in the defence against infections and malignancies. To exert their function, B cells and T cells differentiate into effector and memory cells. Tight regulation of these differentiation processes is key to prevent their malfunction, which can result in life-threatening disease. Lymphocyte differentiation relies on the appropriate timing and dosage of regulatory molecules, and post-transcriptional gene regulation (PTR) is a key player herein. PTR includes the regulation through RNA-binding proteins (RBPs), which control the fate of RNA and its translation into proteins. To date, a comprehensive overview of the RBP expression throughout lymphocyte differentiation is lacking. Using transcriptome and proteome analyses, we here catalogued the RBP expression for human B cells and T cells. We observed that even though the overall RBP expression is conserved, the relative RBP expression is distinct between B cells and T cells. Differentiation into effector and memory cells alters the RBP expression, resulting into preferential expression of different classes of RBPs. For instance, whereas naive T cells express high levels of translation-regulating RBPs, effector T cells preferentially express RBPs that modulate mRNA stability. Lastly, we found that cytotoxic CD8+ and CD4+ T cells express a common RBP repertoire. Combined, our study reveals a cell type-specific and differentiation-dependent RBP expression landscape in human lymphocytes, which will help unravel the role of RBPs in lymphocyte function.

Characteristics of immune function of full-term infants with different feeding patterns at the age of 3 months: a prospective cohort study

OBJECTIVES

To explore the characteristics of immune function of healthy full-term infants at the age of 3 months, and to analyze the relationship of immune function with feeding pattern and sex.

METHODS

A total of 84 healthy full-term infants born in four hospitals in Beijing and Hohhot, China were prospectively recruited. Their feeding patterns remained unchanged within 4 months after birth. They were divided into a breast-feeding group and a milk powder feeding group according to their feeding patterns. At the age of 3 months after birth, peripheral venous blood samples of the two groups were collected to evaluate cellular immunity and humoral immunity and perform routine blood test. The laboratory indices were compared between infants with different feeding patterns and sexes.

RESULTS

Compared with the milk powder feeding group, the breast-feeding group had significantly lower proportion of T cell second signal receptor CD28, immunoglobulin M, and proportion and absolute count of neutrophils (P<0.05) and significantly higher expression and proportion of HLA-DR, a surface activation marker of CD8⁺ T cells, and proportion of lymphocytes (P<0.05). The male infants had a significantly lower white blood cell count and a significantly higher proportion of eosinophils compared with the female infants (P<0.05).

CONCLUSIONS

Sex has no significant effect on the proportion of lymphocyte subsets in 3-month-old full-term infants, but feeding patterns are associated with the proportion of CD28⁺ T cells (lymphocyte functional subset) and HLA-DR⁺ T cells (lymphocyte activation subset), suggesting that feeding patterns have a certain effect on the development of immune function in 3-month-old full-term infants.

Characterization of a Cohort of Patients With LIG4 Deficiency Reveals the Founder Effect of p.R278L, Unique to the Chinese Population

DNA ligase IV (LIG4) deficiency is an extremely rare autosomal recessive primary immunodeficiency disease caused by mutations in LIG4. Patients suffer from a broad spectrum of clinical problems, including microcephaly, growth retardation, developmental delay, dysmorphic facial features, combined immunodeficiency, and a predisposition to autoimmune diseases and malignancy. In this study, the clinical, molecular, and immunological characteristics of 15 Chinese patients with LIG4 deficiency are summarized in detail. p.R278L (c.833G>T) is a unique mutation site present in the majority of Chinese cases. We conducted pedigree and haplotype analyses to examine the founder effect of this mutation site in China. This suggests that implementation of protocols for genetic diagnosis and for genetic counseling of affected pedigrees is essential. Also, the search might help determine the migration pathways of populations with Asian ancestry.

RAG1 splicing mutation causes enhanced B cell differentiation and autoantibody production

Hypomorphic RAG1 or RAG2 mutations cause primary immunodeficiencies and can lead to autoimmunity, but the underlying mechanisms are elusive. We report here a patient carrying a c.116+2T>G homozygous splice site mutation in the first intron of RAG1, which led to aberrant splicing and greatly reduced RAG1 protein expression. B cell development was blocked at both the pro-B to pre-B transition and the pre-B to immature B cell differentiation step. The patient B cells had reduced B cell receptor repertoire diversity and decreased complementarity determining region 3 lengths. Despite B cell lymphopenia, the patient had abundant plasma cells in the BM and produced large quantities of IgM and IgG Abs, including autoantibodies. The proportion of naive B cells was reduced while the frequency of IgD^–CD27^– double-negative (DN) B cells, which quickly differentiated into Ab-secreting plasma cells upon stimulation, was greatly increased. Immune phenotype analysis of 52 patients with primary immunodeficiency revealed a strong association of the increased proportion of DN B and memory B cells with decreased number and proportion of naive B cells. These results suggest that the lymphopenic environment triggered naive B cell differentiation into DN B and memory B cells, leading to increased Ab production.

The development of autoverification system of lymphocyte subset assays on the flow cytometry platform

OBJECTIVES

Peripheral blood lymphocyte subsets are important parameters for monitoring immune status; however, lymphocyte subset detection is time-consuming and error-prone. This study aimed to explore a highly efficient and clinically useful autoverification system for lymphocyte subset assays performed on the flow cytometry platform.

METHODS

A total of 94,402 lymphocyte subset test results were collected. To establish the limited-range rules, 80,427 results were first used (69,135 T lymphocyte subset tests and 11,292 NK, B, T lymphocyte tests), of which 15,000 T lymphocyte subset tests from human immunodeficiency virus (HIV) infected patients were used to set customized limited-range rules for HIV infected patients. Subsequently, 13,975 results were used for historical data validation and online test validation.

RESULTS

Three key autoverification rules were established, including limited-range, delta-check, and logical rules. Guidelines for addressing the issues that trigger these rules were summarized. The historical data during the validation phase showed that the total autoverification passing rate of lymphocyte subset assays was 69.65% (6,941/9,966), with a 67.93% (5,268/7,755) passing rate for T lymphocyte subset tests and 75.67% (1,673/2,211) for NK, B, T lymphocyte tests. For online test validation, the total autoverification passing rate was 75.26% (3,017/4,009), with 73.23% (2,191/2,992) for the T lymphocyte subset test and 81.22% (826/1,017) for the NK, B, T lymphocyte test. The turnaround time (TAT) was reduced from 228 to 167 min using the autoverification system.

CONCLUSIONS

The autoverification system based on the laboratory information system for lymphocyte subset assays reduced TAT and the number of error reports and helped in the identification of abnormal cell populations that may offer clues for clinical interventions.

Single-cell RNA sequencing of peripheral blood mononuclear cells from acute Kawasaki disease patients

Kawasaki disease (KD) is the most common cause of acquired heart disease in children in developed countries. Although functional and phenotypic changes of immune cells have been reported, a global understanding of immune responses underlying acute KD is unclear. Here, using single-cell RNA sequencing, we profile peripheral blood mononuclear cells from seven patients with acute KD before and after intravenous immunoglobulin therapy and from three age-matched healthy controls. The most differentially expressed genes are identified in monocytes, with high expression of pro-inflammatory mediators, immunoglobulin receptors and low expression of MHC class II genes in acute KD. Single-cell RNA sequencing and flow cytometry analyses, of cells from an additional 16 KD patients, show that although the percentage of total B cells is substantially decreased after therapy, the percentage of plasma cells among the B cells is significantly increased. The percentage of CD8+ T cells is decreased in acute KD, notably effector memory CD8+ T cells compared with healthy controls. Oligoclonal expansions of both B cell receptors and T cell receptors are observed after therapy. We identify biological processes potentially underlying the changes of each cell type. The single-cell landscape of both innate and adaptive immune responses provides insights into pathogenesis and therapy of KD.

Variation of B cell subsets with age in healthy Malawians

Although a number of previous studies have shown that different lymphocyte subsets, including B cells, vary with age, how different B cell subsets vary with age in Malawian population has not been shown before. We recruited Malawian participants of different ages and analyzed their venous blood samples for different B cell subsets. We found that both percentage and absolute counts of B cells varied with age peaking in the 7 to 12 months age group. Proportion of naïve B cells was highest in neonates and decreased with age whereas the percentage of memory B cells was lowest in neonates and increased with age. When we zeroed in on the age band within which the proportion of B cells was highest, both classical and activated memory B cells increased with age and the naïve followed the opposite trend. These results provide additional knowledge in our understanding of the dynamics of B cell subsets in individuals of a specific ethnicity as they age.

Direct Measurement of B Lymphocyte Gene Expression Biomarkers in Peripheral Blood Transcriptomics Enables Early Prediction of Vaccine Seroconversion

Peripheral blood transcriptome is a highly promising area for biomarker development. However, transcript abundances (TA) in these cell mixture samples are confounded by proportions of the component leukocyte subpopulations. This poses a challenge to clinical applications, as the cell of origin of any change in TA is not known without prior cell separation procedure. We developed a framework to develop a cell-type informative TA biomarkers which enable determination of TA of a single cell-type (B lymphocytes) directly in cell mixture samples of peripheral blood (e.g., peripheral blood mononuclear cells, PBMC) without the need for subpopulation separation. It is applicable to a panel of genes called B cell informative genes. Then a ratio of two B cell informative genes (a target gene and a stably expressed reference gene) obtained in PBMC was used as a new biomarker to represent the target gene expression in purified B lymphocytes. This approach, which eliminates the tedious procedure of cell separation and directly determines TA of a leukocyte subpopulation in peripheral blood samples, is called the Direct LS-TA method. This method is applied to gene expression datasets collected in influenza vaccination trials as early predictive biomarkers of seroconversion. By using TNFRSF17 or TXNDC5 as the target genes and TNFRSF13C or FCRLA as the reference genes, the Direct LS-TA B cell biomarkers were determined directly in the PBMC transcriptome data and were highly correlated with TA of the corresponding target genes in purified B lymphocytes. Vaccination responders had almost a 2-fold higher Direct LS-TA biomarker level of TNFRSF17 (log 2 SMD = 0.84, 95% CI = 0.47–1.21) on day 7 after vaccination. The sensitivity of these Direct LS-TA biomarkers in the prediction of seroconversion was greater than 0.7 and area-under curves (AUC) were over 0.8 in many datasets. In this paper, we report a straightforward approach to directly estimate B lymphocyte gene expression in PBMC, which could be used in a routine clinical setting. Moreover, the method enables the practice of precision medicine in the prediction of vaccination response. More importantly, seroconversion could now be predicted as early as day 7. As the acquired immunology pathway is common to vaccination against influenza and COVID-19, these biomarkers could also be useful to predict seroconversion for the new COVID-19 vaccines.

Case Report: Expanding Clinical, Immunological and Genetic Findings in Sideroblastic Anemia With Immunodeficiency, Fevers and Development Delay (SIFD) Syndrome

Since the first description of the syndrome of sideroblastic anemia with immunodeficiency, fevers and development delay (SIFD), clinical pictures lacking both neurological and hematological manifestations have been reported. Moreover, prominent skin involvement, such as with relapsing erythema nodosum, is not a common finding. Up to this moment, no genotype and phenotype correlation could be done, but mild phenotypes seem to be located in the N or C part. B-cell deficiency is a hallmark of SIFD syndrome, and multiple others immunological defects have been reported, but not high levels of double negative T cells. Here we report a Brazilian patient with a novel phenotype of SFID syndrome, carrying multiple immune defects and harboring a novel mutation on TRNT1 gene.

Immunophenotypic analysis of lymphocyte subsets in newborns with biotinidase deficiency

BACKGROUND/AIM

Biotin is a vital micronutrient that plays a role in metabolic homeostasis and the regulation of innate and adaptive immune system functions. Biotinidase deficiency (BTD) leads to impairment in biotin-dependent immune functions. This study focused on immunophenotypic analysis of lymphocyte subsets in newborns with BTD.

PATIENTS AND METHODS

A total of 181 (95 female and 86 male; 114 had BTD and 67 were healthy) newborns underwent biotinidase enzyme activity, molecular and lymphocyte immunophenotyping analyses. BTD is classified into four biochemical phenotypes: profound, partial, heterozygous and normal. The following lymphocyte subsets were studied in all participants: total B lymphocyte (CD19), total T lymphocyte (CD3), helper T lymphocyte (CD3/CD4), cytotoxic T lymphocyte (CTL) (CD3/CD8), natural killer T lymphocyte (CD16/56) and a T-lymphocyte activation marker (HLA-DR).

RESULTS

The percentages of lymphocyte subsets were similar in newborns with and without BTD. In all newborns with BTD, the mean CD3/CD4 levels were higher in females, while the CD3/CD8 levels were higher in males (P < .001 for each). In female and male newborns, the CD3/CD4 levels were 53.83 ± 9.46 and 16.82 ± 5.19, respectively, and the CD3/CD8 levels were 48.80 ± 8.65 and 21.48 ± 6.02, respectively. A moderate negative correlation was found between CD3/CD4 and CD3/CD8 in female and male newborns (r_female  = -0.488, r_male  = -0.574, P < .001).

CONCLUSION

This study showed that although there were no differences in the lymphocyte subsets in newborns with BTD, the CD3/CD4 levels were higher in females, and the CD3/CD8 levels were higher in males. In addition, there was a negative correlation between the CD3/CD4 and CD3/CD8 levels in both genders. Although these results indicate sexual dimorphism between CD3/CD4 and CD3/CD8 levels, whether this dissociation is unique to BTD in newborns is not fully clear.

Saliva viral load better correlates with clinical and immunological profiles in children with coronavirus disease 2019

Background

Pediatric COVID-19 studies exploring the relationships between NPS and saliva viral loads, clinical and immunological profiles are lacking.

Methods

Demographics, immunological profiles, nasopharyngeal swab (NPS), and saliva samples collected on admission, and hospital length of stay (LOS) were assessed in children below 18 years with COVID-19.

Findings

91 patients were included between March and August 20 20. NPS and saliva viral loads were correlated (r = 0.315, p = 0.01). Symptomatic patients had significantly higher NPS and saliva viral loads than asymptomatic patients. Serial NPS and saliva viral load measurements showed that the log₁₀ NPS (r = −0.532, p < 0.001) and saliva (r = −0.417, p < 0.001) viral loads for all patients were inversely correlated with the days from symptom onset with statistical significance. Patients with cough, sputum, and headache had significantly higher saliva, but not NPS, viral loads. Higher saliva, but not NPS, viral loads were associated with total lymphopenia, CD3 and CD4 lymphopenia (all p < 0.05), and were inversely correlated with total lymphocyte (r = −0.43), CD3 (r = −0.55), CD4 (r = −0.60), CD8 (r = −0.41), B (r = −0.482), and NK (r = −0.416) lymphocyte counts (all p < 0.05).

Interpretation

Saliva viral loads on admission in children correlated better with clinical and immunological profiles than NPS.

A Novel Homozygous Mutation Destabilizes IKKβ and Leads to Human Combined Immunodeficiency

Mutations in the IKBKB gene cause severe immunodeficiency, characterized clinically by persistent respiratory or gastrointestinal infections. Targeted gene panel sequencing revealed a novel homozygous missense mutation in the IKBKB gene of a patient with immune dysregulation and combined T and B cell functional defects. PBMCs from the patient, Ikbkb Y397H mice, and transfected cells were used to elucidate how the Y395H mutation triggers IKKβ deficiency and impairs immune function. Here, we found that cells from both the patient and Ikbkb Y397H mice lacked or showed decreased levels of IKKβ protein, along with impaired lymphocyte function. IKKα and IKKγ protein expression by human PBMCs harboring the Y395H mutation was normal, but degradation of IKKβ protein was accelerated. Binding of human NF-κB to DNA in patient PBMCs fell upon stimulation with TNF-α or LPS. Additionally, a structural model of Y395H revealed loss of the hydrogen bond with D389. These data suggest that IKBKB deficiency induces abnormal IKKβ protein degradation, leading to impaired NF-κB signaling and immune function. We postulate that the Y395H variant in the IKKβ protein lost the hydrogen bond with D389, thereby affecting interaction between Y395 and D389 and increasing protein instability.