Immunophenotyping of blood lymphocytes in childhood. Reference values for lymphocyte subpopulations

Neonatal Outcomes following 2 Cases of Maternal CAR-T Therapy for High-Grade B-Cell Lymphoma

INTRODUCTION

Chimeric antigen receptor T cells (CAR-Ts) targeting CD19 represent a significant advance in treatment for patients with relapsed/refractory B-cell malignancies. Although a significant minority of recipients are women during their reproductive years, there is a paucity of data regarding pregnancy and neonatal outcomes in women previously treated with CAR-T. This is important as maternal T cells are known to cross the placenta and into breastmilk during pregnancy and breastfeeding, respectively.

CASE PRESENTATION

Here we present two successful pregnancies following CAR-T therapy where both neonates were initially breastfed. These represent the first cases of neonates born following CAR-T therapy comprehensively described in medical literature.

CONCLUSION

Pregnancy following CAR-T therapy does not appear to be associated with adverse neonatal outcomes. Further work is required to delineate the outcomes in this population.

Application and interpretation of immunophenotyping data in safety and risk assessment

The use of immunophenotyping during immunotoxicity investigations was first popularized in the 1980 s and has since become more integrated into diagnostic and non-clinical assessments. The data provided from immunophenotyping can serve as an initial source of information to guide decisions for additional, more advanced, immunotoxicity testing as well as for human health safety and risk assessment of drugs and chemicals. However, comprehensive guidance describing applications of immunophenotyping data in immunotoxicity investigations is lacking, particularly among regulatory bodies. Therefore, a critical examination is needed for the appropriate interpretations and potential misinterpretations of such data during the assessment of drug safety and chemical risk. As such, the current uses and implications of immunophenotyping data in human health safety and risk assessments has been evaluated to provide additional context for the application of current methodologies and guidelines. In addition, case studies are presented to highlight the challenges of interpreting immunophenotyping results along with incorporating the findings into immunotoxicity investigations. Based on the analyses of current approaches and methodologies, a decision flow is presented for use of immunophenotyping data during risk informed decision making.

From Pancytopenia to Hyperleukocytosis, an Unexpected Presentation of Immune Reconstitution Inflammatory Syndrome in an Infant with Methylmalonic Acidemia

A 2.5-month-old girl admitted for failure to thrive and severe pancytopenia was diagnosed with methylmalonic acidemia (MMA) secondary to transcobalamin II deficiency, an inborn error of vitamin B12 metabolism. Opportunistic Cytomegalovirus and Pneumocystis jirovecii pneumonia led to severe acute respiratory distress syndrome (ARDS) and immune reconstitution inflammatory syndrome (IRIS) after treatment initiation with vitamin B12 supplementation. In children with interstitial pneumonia-related ARDS, normal lymphocyte count should not delay invasive procedures required to document opportunistic infections. MMA can be associated with underlying lymphocyte dysfunction and vitamin B12 supplementation can fully reverse the associated immunodeficiency. IRIS may appear in highly treatment-responsive forms of pancytopenia in children and prompt treatment of dysregulated inflammation with high-dose corticosteroids should be initiated.

A Critical Role of Culture Medium Selection in Maximizing the Purity and Expansion of Natural Killer Cells

Natural killer (NK) cells hold promise in cancer treatment due to their ability to spontaneously lyse cancer cells. For clinical use, high quantities of pure, functional NK cells are necessary. Combining adherence-based isolation with specialized media showed the unreliability of the isolation method, but demonstrated the superiority of the NK MACS® medium, particularly in suboptimal conditions. Neither human pooled serum, fetal calf serum (FCS), human platelet lysate, nor chemically defined serum replacement could substitute human AB serum. Interleukin (IL-)2, IL-15, IL-21, and combined CD2/NKp46 stimulation were assessed. IL-21 and CD2/NKp46 stimulation increased cytotoxicity, but reduced NK cell proliferation. IL-15 stimulation alone achieved the highest proliferation, but the more affordable IL-2 performed similarly. The RosetteSep™ human NK cell enrichment kit was effective for isolation, but the presence of peripheral blood mononuclear cells (PBMCs) in the culture enhanced NK cell proliferation, despite similar expression levels of CD16, NKp46, NKG2D, and ICAM-1. In line with this, purified NK cells cultured in NK MACS® medium with human AB serum and IL-2 demonstrated high cytotoxicity against primary glioblastoma stem cells.

Minimal residual disease assessment in B-cell precursor acute lymphoblastic leukemia by semi-automated identification of normal hematopoietic cells: A EuroFlow study

Presence of minimal residual disease (MRD), detected by flow cytometry, is an important prognostic biomarker in the management of B-cell precursor acute lymphoblastic leukemia (BCP-ALL). However, data-analysis remains mainly expert-dependent. In this study, we designed and validated an Automated Gating & Identification (AGI) tool for MRD analysis in BCP-ALL patients using the two tubes of the EuroFlow 8-color MRD panel. The accuracy, repeatability, and reproducibility of the AGI tool was validated in a multicenter study using bone marrow follow-up samples from 174 BCP-ALL patients, stained with the EuroFlow BCP-ALL MRD panel. In these patients, MRD was assessed both by manual analysis and by AGI tool supported analysis. Comparison of MRD levels obtained between both approaches showed a concordance rate of 83%, with comparable concordances between MRD tubes (tube 1, 2 or both), treatment received (chemotherapy versus targeted therapy) and flow cytometers (FACSCanto versus FACSLyric). After review of discordant cases by additional experts, the concordance increased to 97%. Furthermore, the AGI tool showed excellent intra-expert concordance (100%) and good inter-expert concordance (90%). In addition to MRD levels, also percentages of normal cell populations showed excellent concordance between manual and AGI tool analysis. We conclude that the AGI tool may facilitate MRD analysis using the EuroFlow BCP-ALL MRD protocol and will contribute to a more standardized and objective MRD assessment. However, appropriate training is required for the correct analysis of MRD data.

Exploring immune status in peripheral blood and tumor tissue in association with survival in patients with multi-organ metastatic colorectal cancer

Colorectal cancer (CRC) raises considerable clinical challenges, including a high mortality rate once the tumor spreads to distant sites. At this advanced stage, more accurate prediction of prognosis and treatment outcome is urgently needed. The role of cancer immunity in metastatic CRC (mCRC) is poorly understood. Here, we explore cellular immune cell status in patients with multi-organ mCRC. We analyzed T cell infiltration in primary tumor sections, surveyed the lymphocytic landscape of liver metastases, and assessed circulating mononuclear immune cells. Besides asking whether immune cells are associated with survival at this stage of the disease, we investigated correlations between the different tissue types; as this could indicate a dominant immune phenotype. Taken together, our analyses corroborate previous observations that higher levels of CD8+ T lymphocytes link to better survival outcomes. Our findings therefore extend evidence from earlier stages of CRC to indicate an important role for cancer immunity in disease control even after metastatic spreading to multiple organs. This finding may help to improve predicting outcome of patients with mCRC and suggests a future role for immunotherapeutic strategies.

Engineering CD3/CD137 Dual Specificity into a DLL3-Targeted T-Cell Engager Enhances T-Cell Infiltration and Efficacy against Small-Cell Lung Cancer

Small-cell lung cancer (SCLC) is an aggressive cancer for which immune checkpoint inhibitors (ICI) have had only limited success. Bispecific T-cell engagers are promising therapeutic alternatives for ICI-resistant tumors, but not all patients with SCLC are responsive. Herein, to integrate CD137 costimulatory function into a T-cell engager format and thereby augment therapeutic efficacy, we generated a CD3/CD137 dual-specific Fab and engineered a DLL3-targeted trispecific antibody (DLL3 trispecific). The CD3/CD137 dual-specific Fab was generated to competitively bind to CD3 and CD137 to prevent DLL3-independent cross-linking of CD3 and CD137, which could lead to systemic T-cell activation. We demonstrated that DLL3 trispecific induced better tumor growth control and a marked increase in the number of intratumoral T cells compared with a conventional DLL3-targeted bispecific T-cell engager. These findings suggest that DLL3 trispecific can exert potent efficacy by inducing concurrent CD137 costimulation and provide a promising therapeutic option for SCLC.

Long-term lymphocyte subset number reconstitution is unique but comparable between umbilical cord blood and unrelated bone marrow transplantation

The number of umbilical cord blood transplantation (U-CBT) procedures has been growing annually, but little research has been done on long-term immune recovery after U-CBT. Infection risk is high in U-CBT recipients, and this can be partially attributed to immature immunocompetent cells in umbilical cord blood. In this study, we analyzed lymphocyte subset (LST) number to determine the long-term recovery timeline. We included 36 U-CBT and 10 unrelated bone marrow transplantation (U-BMT) recipients who survived more than 2 years after transplantation, and followed them for up to 10 years post-transplant. Recovery kinetics in the early phase post-transplant was different for each LST. Recovery of CD19+ B cells was faster after U-CBT than after U-BMT in the first 5 years after transplantation. Although CD4+ T cells increased in the first several months after U-CBT, long-term cell count recovery was impaired in approximately 20% of patients. Thus, although the LST recovery pattern after U-CBT was unique, LST number recovery was statistically comparable between U-CBT and U-BMT past 5 years post-transplantation.

Evolution of CD4 T-Cell Count With Age in a Cohort of Young People Growing Up With Perinatally Acquired Human Immunodeficiency Virus

BACKGROUND

Recent studies have shown a decrease in CD4 count during adolescence in young people with perinatally acquired human immunodeficiency virus (HIV, PHIV).

METHODS

Young people with PHIV in the United Kingdom, followed in the Collaborative HIV Paediatric Study who started antiretroviral therapy (ART) from 2000 onward were included. Changes in CD4 count over time from age 10 to 20 years were analyzed using mixed-effects models, and were compared to published CD4 data for the gerneral population. Potential predictors were examined and included demographics, age at ART start, nadir CD4 z score (age-adjusted) in childhood, and time-updated viral load.

RESULTS

Of 1258 young people with PHIV included, 669 (53%) were female, median age at ART initiation was 8.3 years, and the median nadir CD4 z score was -4.0. Mean CD4 count was higher in young people with PHIV who started ART before age 10 years and had a nadir CD4 z score ≥-4; these young people with PHIV had a decline in CD4 count after age 10 that was comparable to that of the general population. Mean CD4 count was lower in young people with PHIV who had started ART before age 10 and had a nadir CD4 z score <-4; for this group, the decline in CD4 count after age 10 was steeper over time.

CONCLUSIONS

In children, in addition to starting ART at an early age, optimizing ART to maintain a higher CD4 z score during childhood may be important to maximizing immune reconstitution later in life.

Young infants display heterogeneous serological responses and extensive but reversible transcriptional changes following initial immunizations

Infants necessitate vaccinations to prevent life-threatening infections. Our understanding of the infant immune responses to routine vaccines remains limited. We analyzed two cohorts of 2-month-old infants before vaccination, one week, and one-month post-vaccination. We report remarkable heterogeneity but limited antibody responses to the different antigens. Whole-blood transcriptome analysis in an initial cohort showed marked overexpression of interferon-stimulated genes (ISGs) and to a lesser extent of inflammation-genes at day 7, which normalized one month post-vaccination. Single-cell RNA sequencing in peripheral blood mononuclear cells from a second cohort identified at baseline a predominantly naive immune landscape including ISGhi cells. On day 7, increased expression of interferon-, inflammation-, and cytotoxicity-related genes were observed in most immune cells, that reverted one month post-vaccination, when a CD8+ ISGhi and cytotoxic cluster and B cells expanded. Antibody responses were associated with baseline frequencies of plasma cells, B-cells, and monocytes, and induction of ISGs at day 7.

Oral immunotherapy as a curative treatment for food-allergic preschool children: Current evidence and potential underlying mechanisms

The worldwide rising prevalence of food allergy is a major public health concern. Standard care consists of allergen avoidance and rescue medication upon accidental exposure. Oral immunotherapy (OIT) is increasingly being studied as a treatment option. Although desensitization (an increased reaction threshold) is often achieved during OIT, sustained unresponsiveness (SU; clinical nonreactivity after finishing OIT) is not achieved in most patients. A few studies have investigated the effectiveness of OIT in children younger than 4 years of age (early = e-OIT) and have shown a much more favorable outcome in terms of SU development. Together with food allergy prevention studies, which have demonstrated high efficacy of early oral allergen exposure, the outcomes of e-OIT studies indicate an early-life window of opportunity to achieve SU, allowing unrestricted dietary intake. However, the underlying mechanism of the high effectiveness of e-OIT is not understood yet. Both cohort and OIT studies indicate early-life immune plasticity. An immature food-allergic response in the first years of life seems to be a major driver of this immune plasticity, along with a higher tolerogenic immunological state. Allergy maturation can likely be disrupted effectively by early intervention, preventing the development of persistent food allergy. Upcoming studies will provide important additional data on the safety, feasibility, and effectiveness of e-OIT. Combined with immune mechanistic studies, this should inform the implementation of e-OIT.

Respiratory Comorbidities Associated with Bronchiectasis in Patients with Common Variable Immunodeficiency in the USIDNET Registry

BACKGROUND

Bronchiectasis is a major respiratory complication in patients with common variable immunodeficiency (CVID) and is associated with recurrent pulmonary infections. However, it is unclear whether other infections or non-infectious respiratory conditions are related to its development.

OBJECTIVE

To identify respiratory comorbidities associated with bronchiectasis in patients with CVID.

METHODS

A total of 1470 CVID patients enrolled in the USIDNET registry were included in a cross-sectional analysis. The primary outcome of our study was to determine the clinical characteristics and other respiratory conditions associated with respiratory comorbidities and physician-reported bronchiectasis.

RESULTS

One hundred ninety-seven CVID patients were noted to have bronchiectasis (13.4%). Affected patients were significantly older than patients without bronchiectasis (median age 54 years vs. 49 years, p = 0.0004). These patients also had lower serum IgA (13 mg/dL IQR 60 mg/dL vs. 28.4 mg/dL IQR 66 mg/dL, p = 0.000). Notably, chronic rhinosinusitis (OR = 1.69 95%CI 1.05-2.75), sinusitis (OR = 2.06 95%CI 1.38-3.09), pneumonia (OR = 2.70 95%CI 1.88-3.88), COPD (OR = 2.66 95%CI 1.51-4.67), and interstitial lung disease (OR = 2.34 95%CI 1.41-3.91) were independently associated with the development of bronchiectasis in this population.

CONCLUSION

These data suggest that lower and upper respiratory infections, chronic lower airway disease, and interstitial lung diseases are independently associated with bronchiectasis in CVID patients. Further study into predisposing conditions related to the development of bronchiectasis in CVID patients may allow prediction and early intervention strategies to prevent the development of this complication.

Allergic Disease with Selective IgA Deficiency. Comment on Cinicola et al. The Allergic Phenotype of Children and Adolescents with Selective IgA Deficiency: A Longitudinal Monocentric Study. J. Clin. Med. 2022, 11, 5705

I read the article titled 'The Allergic Phenotype of Children and Adolescents with Selective IgA Deficiency: A Longitudinal Monocentric Study' by Cinicola et al. with great interest [...].

Clinical and immunological phenotypes of selective IgM deficiency in children: Results from a multicenter study

BACKGROUND

A few studies assessed the clinical and immunological features of selective IgM deficiency (SIgMD), especially in the pediatric age. We aimed to characterize the clinical and immunological phenotypes of a cohort of pediatric patients with SIgMD according to the different diagnostic criteria available.

METHODS

In this multicenter study, we evaluated pediatric SIgMD patients diagnosed at the Pediatric Clinic in Pavia, Italy, or through the Italian Primary Immunodeficiency NETwork (IPINET) and monitored changes in their diagnosis over a time frame that ranges from several months to several years.

RESULTS

Forty-eight patients with SIgMD were included (mean serum IgM: 33 mg/dL). The most common clinical manifestations were recurrent infections (67%) and allergies (48%). Subgroup analysis according to SIgMD definition criteria of the European Society for Immunodeficiencies (ESID) showed no significant difference in clinical manifestations, also considering the group with additional immunological abnormalities. Sixteen patients had long-term follow-up, during which 87% preserved their SIgMD diagnosis, while two patients showed a reduction in IgA in addition to low IgM.

CONCLUSIONS

Our data suggest that the identification of a reduction in serum IgM in children should lead to a complete immunological work-up to obtain a comprehensive clinical and immunological characterization of the patient. The follow-up of these patients is fundamental to define the disease evolution and appropriate management.

Sex Differences in the Frequencies of B and T Cell Subpopulations of Human Cord Blood

Cord blood represents a link between intrauterine and early extrauterine development. Cord blood cells map an important time frame in human immune imprinting processes. It is unknown whether the sex of the newborn affects the lymphocyte subpopulations in the cord blood. Nine B and twenty-one T cell subpopulations were characterized using flow cytometry in human cord blood from sixteen male and twenty-one female newborns, respectively. Except for transitional B cells and naïve B cells, frequencies of B cell counts across all subsets was higher in the cord blood of male newborns than in female newborns. The frequency of naïve thymus-negative Th cells was significantly higher in male cord blood, whereas the remaining T cell subpopulations showed a higher count in the cord blood of female newborns. Our study is the first revealing sex differences in the B and T cell subpopulations of human cord blood. These results indicate that sex might have a higher impact for the developing immune system, urging the need to expand research in this area.

Role of the immune system in amyotrophic lateral sclerosis. Analysis of the natural killer cells and other circulating lymphocytes in a cohort of ALS patients

AIMS

Neuroinflammation might be involved in the degeneration and progression of Amyotrophic Lateral Sclerosis (ALS). Here, we studied the role of the circulating lymphocytes in ALS, in particular the NK cells. We focused on the relationship between blood lymphocytes, ALS clinical subtype and disease severity.

SUBJECTS AND METHODS

Blood samples were collected from 92 patients with sporadic ALS, 21 patients with Primary Lateral Sclerosis (PLS) and 37 patients affected by primary progressive multiple sclerosis (PPMS) with inactive plaques. Blood was taken from ALS and controls at the time of diagnosis/referral. Circulating lymphocytes were analyzed by flow cytometry with specific antibodies. Values were expressed as absolute number (n°/µl) of viable lymphocytes subpopulations in ALS were compared with controls. Multivariable analysis was made using site of onset, gender changes in ALSFRS-R and disease progression rate (calculated as ΔFS score).

RESULTS

Age at onset was 65y (58-71) in ALS (spinal 67.4%; bulbar, 32.6%), 57y (48-78) in PLS and 56y (44-68) PPMS. Absolute blood levels of the lymphocytes in the different cohorts were within normal range. Furthermore, while levels of lymphocytes T and B were not different between disease groups, NK cells were increased in the ALS cohort (ALS = 236 [158-360] vs. Controls = 174[113-240], p < 0.001). In ALS, blood levels of NK cells were not related with the main clinical-demographic variables, including the rate of disease progression. Multivariable analysis suggested that male gender and bulbar onset were independently associated with a risk of high blood NK cells levels.

CONCLUSIONS

We show that blood NK cells are selectively increased in ALS, though their level appear unaffected in patients with an estimated rapidly progressing disease. Being of a male gender and with a bulbar onset seems to confer higher susceptibility to have increased NK lymphocytes levels at diagnosis/referral. Our experiments provides a further clear-cut evidence of the role of the NK lymphocytes as a significant player in ALS pathogenesis.

Poikilocytosis of Angora goats is associated with erythrocyte density and reticulocytosis

Angora goats in South Africa experience several syndromes that result in notable morbidity and mortality in juveniles and adults, but not kids. Insight into their causes is hampered by the lack of normal reference values for this breed, and the present study therefore aimed to characterise (1) differences in the haematology of healthy kids at birth and weaning, and (2) the haematology of apparently healthy yearlings. Selected variables were measured by blood smear analysis, and complete blood counts were performed using an ADVIA 2120i. Variables at 1, 11, and 20 weeks of age were compared using the Friedman test and associations between variables of yearlings were determined by correlation analysis. In kids, red blood cell count, mean corpuscular haemoglobin concentration (MCHC), and poikilocytosis increased over time, while mean corpuscular haemoglobin (MCH) and mean corpuscular volume (MCV) decreased. Yearlings displayed a lower MCHC, and higher haemoglobin distribution width than previously reported for goats, and these were positively correlated with poikilocytosis, as were reticulocyte counts. White cell counts of yearlings exceeded normal values previously reported for goats, with some individuals displaying remarkably high mature neutrophil counts. Changes in haemoglobin variant expression or cation and water fluxes are possible explanations for the findings in kids, while in yearlings, the associations between MCHC, HDW, poikilocytosis, and reticulocytosis suggest alterations in red cell hydration in adulthood that are associated with increased red cell turnover. These findings may prove informative in the further investigation of various clinical syndromes in this population.

Mitochondrial DNA copy number dynamics and associations with the prenatal environment from birth through adolescence in a population of Dominican and African American children

Mitochondrial DNA copy number (mtDNAcn) dynamics throughout childhood are poorly understood. We profiled mtDNAcn from birth through adolescence and evaluated how the prenatal environment influences mtDNAcn across childhood. Data were collected from children from New York City followed through 18 years. Using duplexed qRT-PCR, we quantified mtDNAcn relative to nuclear DNA in blood collected from the umbilical cord (n = 450), children aged 5-7 (n = 510), and adolescents aged 15-18 (n = 278). We examined mtDNAcn across childhood with linear mixed-effects models (LMM). Relative mtDNAcn was lowest at birth (mean ± SD: 0.67 ± 0.35) and increased in childhood (1.24 ± 0.50) then slightly declined in adolescence (1.13 ± 0.44). We observed no differences in mtDNAcn by sex or race/ethnicity. mtDNAcn was positively associated with prenatal environmental tobacco smoke exposure (0.077 [ 0.01, 0.14] change in relative mtDNAcn) but negatively associated with maternal completion of high school (-0.066 [-0.13, 0.00]), with the receipt of public assistance at birth (-0.074 [-0.14, -0.01]), and when mother born outside the U.S (-0.061 [-0.13, 0.003]). Infant birth outcomes were not associated with mtDNAcn. MtDNAcn levels were dynamic through childhood and associated with some prenatal factors, underscoring the need for the investigation of longitudinal mtDNAcn for human health research.

The Composite Immune Risk Score predicts overall survival after allogeneic hematopoietic stem cell transplantation: A retrospective analysis of 1838 cases

There has been little consensus on how to quantitatively assess immune reconstitution after hematopoietic stem cell transplantation (HSCT) as part of the standard of care. We retrospectively analyzed 11 150 post-transplant immune profiles of 1945 patients who underwent HSCT between 2012 and 2020. 1838 (94.5%) of the cases were allogeneic HSCT. Using the training set of patients (n = 729), we identified a composite immune signature (integrating neutrophil, total lymphocyte, natural killer, total T, CD4+ T, and B cell counts in the peripheral blood) during days 91-180 after allogeneic HSCT that was predictive of early mortality and moreover simplified it into a formula for a Composite Immune Risk Score. When we verified the Composite Immune Risk Score in the validation (n = 284) and test (n = 391) sets of patients, a high score value was found to be associated with hazard ratios (HR) of 3.64 (95% C.I. 1.55-8.51; p = .0014) and 2.44 (95% C.I., 1.22-4.87; p = .0087), respectively, for early mortality. In multivariate analysis, a high Composite Immune Risk Score during days 91-180 remained an independent risk factor for early mortality after allogeneic HSCT (HR, 1.80; 95% C.I., 1.28-2.55; p = .00085). In conclusion, the Composite Immune Risk Score is easy to compute and could identify the high-risk patients of allogeneic HSCT who require targeted effort for prevention and control of infection.

Adoption is not associated with immunological and virological outcomes in children with perinatally acquired HIV infection in the Netherlands

OBJECTIVES

To provide an overview of the demographics, treatment characteristics and long-term outcomes of children with perinatal HIV-1 infection (PHIV) living in the Netherlands (NL) and to specifically investigate whether outcomes differ by children's adoption status.

DESIGN

A prospective population-based open cohort including children with PHIV in NL.

METHODS

We included children with PHIV who had entered HIV care in NL since 2007, in view of a sharp increase in the number of adopted children with PHIV since that year. We compared the proportion with virologic suppression and CD4+T-cell count over time between the following groups of children with PHIV: adopted and born outside NL, non-adopted born in NL, and non-adopted born outside NL, using generalized estimating equations and linear mixed effects models, respectively. To account for the variation in cohort inclusion, we analyzed data of children exposed to at least one year of antiretroviral therapy (ART).

RESULTS

We included 148 children (827.5 person-years of follow-up, 72% adopted, age at start care in NL 2.4 (0.5-5.3)). Under-18 mortality was zero. Over the years, a boosted PI-based regimen was most often prescribed. The use of integrase inhibitors increased since 2015. Non-adopted children born in NL were less likely to achieve virological suppression compared to adopted children (OR 0.66, 95%CI 0.51-0.86, p = 0.001), which disappeared after excluding one child with suspected treatment nonadherence (OR 0.85, 95%CI 0.57-1.25, p = 0.400). CD4+T-cell Z-score trajectories were not significantly different between groups.

CONCLUSIONS

Despite considerable and increasing diversity of the population of children with PHIV in NL, geographical origin and adoption status do not seem to pose important challenges in achieving good immunological and virological outcomes.

Prevalence and outcome of lymphopenia in the Paediatric Intensive Care Unit: A prospective observational study

AIM

Leukopenia (lymphopenia or neutropenia) may be an important marker of altered immunity and risk in children with critical illness. We aimed to evaluate the prevalence, course, and outcome of leukopenia in children admitted to Paediatric Intensive Care Unit (PICU).

METHODS

All consecutive children (n = 200) admitted to PICU for any reason except malignancy or pre-existing immune deficiency were enrolled during June-August 2018.

RESULTS

Median (interquartile range) age was 2.2 (0.6-8.5) years. About 52% (n = 103) had undergone a surgical procedure; 34% (n = 68) being cardiac surgery. Among medical illnesses, respiratory disorders were the most common (n = 39, 20%). Laboratory confirmed infections were present in 63 (31.5%) children. Leukopenia was identified in 135 (67.5%) children in the first week; 117 (58.5%) had only lymphopenia, 16 (8%) had both lymphopenia and neutropenia, and 2 (1%) had only neutropenia. In 69 children who had follow-up blood counts, lymphopenia resolved in 33 (48%) within 48 h and in another 20 (29%) by 4 days, and in a further 10 (14%) by 7 days. Children with lymphopenia had higher frequency of cardiac surgery, longer cardiopulmonary bypass time, greater need for invasive ventilation and vasopressor/inotrope therapy, and a higher probability of organ failure on day 4 and longer hospital stay.

CONCLUSION

In critically ill children, lymphopenia is very common, often transient, but may be associated with unfavourable outcomes. Further studies with follow-up of blood counts in a larger sample are required to determine the course and outcomes of lymphopenia.

High antibody levels and reduced cellular response in children up to one year after SARS-CoV-2 infection

The COVID-19 course and immunity differ in children and adults. We analyzed immune response dynamics in 28 families up to 12 months after mild or asymptomatic infection. Unlike adults, the initial response is plasmablast-driven in children. Four months after infection, children show an enhanced specific antibody response and lower but detectable spike 1 protein (S1)-specific B and T cell responses than their parents. While specific antibodies decline, neutralizing antibody activity and breadth increase in both groups. The frequencies of S1-specific B and T cell responses remain stable. However, in children, one year after infection, an increase in the S1-specific IgA class switch and the expression of CD27 on S1-specific B cells and T cell maturation are observed. These results, together with the enhanced neutralizing potential and breadth of the specific antibodies, suggest a progressive maturation of the S1-specific immune response. Hence, the immune response in children persists over 12 months but dynamically changes in quality, with progressive neutralizing, breadth, and memory maturation. This implies a benefit for booster vaccination in children to consolidate memory formation.

Protein-losing Enteropathy as a Complication and/or Differential Diagnosis of Common Variable Immunodeficiency

As protein-losing enteropathy (PLE) can lead to hypogammaglobulinemia and lymphopenia, and since common variable immunodeficiency (CVID) is associated with digestive complications, we wondered if (1) PLE could occur during CVID and (2) specific features could help determine whether a patient with antibody deficiency has CVID, PLE, or both. Eligible patients were thus classified in 3 groups: CVID + PLE (n = 8), CVID-only (= 19), and PLE-only (n = 13). PLE was diagnosed using fecal clearance of α1-antitrypsin or 111In-labeled albumin. Immunoglobulin (Ig) A, G, and M, naive/memory B and T cell subsets were compared between each group. CVID + PLE patients had multiple causes of PLE: duodenal villous atrophy (5/8), nodular follicular hyperplasia (4/8), inflammatory bowel disease-like (4/8), portal hypertension (4/8), giardiasis (3/8), and pernicious anemia (1/8). Compared to the CVID-only group, CVID + PLE patients had similar serum Ig levels, B cell subset counts, but lower naive T cell proportion and IgG replacement efficiency index. Compared to the CVID-only group, PLE-only patients did not develop infections but had higher serum levels of IgG (p = 0.03), IgA (p < 0.0001), and switched memory B cells (p = 0.001); and decreased naive T cells (CD4⁺: p = 0.005; CD8⁺: p < 0.0001). Compared to the PLE-only group, CVID + PLE patients had higher infection rates (p = 0.0003), and lower serum Ig (especially IgA: p < 0.001) and switched memory B cells levels. In conclusion, PLE can occur during CVID and requires higher IgG replacement therapy dosage. PLE can also mimic CVID and is associated with milder immunological abnormalities, notably mildly decreased to normal serum IgA and switched memory B cell levels.

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.

Immunohematological features of free-living Alouatta belzebul (Linnaeus, 1766) red-handed howler monkeys in the Eastern Amazon

The red-handed howler monkey (Alouatta belzebul) is one of the 35 threatened Brazilian primate species found in two highly endangered Brazilian biomes. Their Amazonian native populations have been declining due to exponential deforestation associated with human activities, especially the construction of dams. The studied population (n = 27) was located in the Belo Monte dam Area of Influence. For the first time, we presented hematological parameters and the basic profile of T (CD3) and B (BSAP PAX5) cells by immunocytochemistry. The results supported the hypothesis that the immuno-hematological profile is influenced by sex, age, and season. Eosinophils were significantly higher in females (p = 0.03), monocytes statistically greater in juveniles (p = 0.04), and total plasma protein increased significantly (p > 0.001) during the dry season. Furthermore, adults showed a statistically higher average absolute number of B lymphocytes than young individuals (p = 0.03), in contrast to T lymphocytes. Even without knowing the full history of antigenic exposure, these results not only contribute to elucidating the boundaries between health and disease but may help lay the groundwork for future research into the effects of anthropogenic stress on immune activation.

Immunological imbalance in microcephalic children with congenital Zika virus syndrome

Microcephalic children due congenital Zika virus syndrome (CZS) present neurological symptoms already well described. However, several other alterations can also be observed. Here, we aimed to evaluate the immune system of microcephaly CZS children. We showed that these patients have enlarged thymus, spleen and cervical lymph nodes, analysed by ultrasound and compared to the reference values for healthy children. In the periphery, they have an increase in eosinophil count and morphological alterations as hypersegmented neutrophils and atypical lymphocytes, even in the absence of urinary tract infections, parasitological infections or other current symptomatic infections. Microcephalic children due CZS also have high levels of IFN-γ, IL-2, IL-4, IL-5 and type I IFNs, compared to healthy controls. In addition, this population showed a deficient cellular immune memory as demonstrated by the low reactivity to the tuberculin skin test even though they had been vaccinated with BCG less than 2 years before the challenge with the PPD. Together, our data demonstrate for the first time that CZS can cause alterations in primary and secondary lymphoid organs and also alters the morphology and functionality of the immune system cells, which broadens the spectrum of CZS symptoms. This knowledge may assist the development of specific therapeutic and more efficient vaccination schemes for this population of patients.

Immune Responses to SARS-CoV-2 Vaccination in Young Patients with Anti-CD19 Chimeric Antigen Receptor T Cell-Induced B Cell Aplasia

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines are capable of inducing combined humoral and cellular immunity. Which effect is more relevant for their potent protective effects is unclear, but isolated T cell responses without seroconversion in healthy household members of individuals with Coronavirus disease 19 (COVID-19) suggest that T cell responses effectively protect against clinical infection. Oncologic patients have an outsize risk of unfavorable outcomes after SARS-CoV-2 infection and therefore were prioritized when vaccines first became available, although the quality of their immune response to vaccination was expected to be suboptimal, as has been confirmed in subsequent studies. Inherently, patients with anti-CD19 chimeric antigen receptor (CAR) T cell therapy-mediated B cell aplasia would be incapable of generating humoral responses, so that assessment of the vaccine-induced cellular immunity is all the more important to gauge whether the vaccine can induce meaningful protection. A salient difference between T cell and humoral responses is the former's relative impassiveness to mutations of the antigen, which is more relevant than ever since the advent of the omicron variant. The objective of this study was to assess the immune cell composition and spike protein-specific T cell responses before and after the first and second doses of SARS-CoV-2 mRNA vaccine in a cohort of juvenile CD19 CAR T cell therapy recipients with enduring B cell aplasia. The prospective study included all patients age >12 years diagnosed with multiply relapsed B cell precursor acute lymphoblastic leukemia and treated with anti-CD19 CAR T cell (CAR-T19) therapy in our center. The primary endpoint was the detection of cell-mediated and humoral responses to vaccine (flow cytometry and anti-S immunoglobulin G, respectively). Secondary endpoints included the incidence of vaccine-related grade 3 or 4 adverse events, exacerbation of graft-versus-host disease (GVHD), relapse, and the influence of the vaccine on CAR T cells and lymphocyte subsets. Even though one-half of the patients exhibited subnormal lymphocyte counts and marginal CD4/CD8 ratios, after 2 vaccinations all showed brisk T-cell responsiveness to spike protein, predominantly in the CD4 compartment, which quantitatively was well within the range of healthy controls. No severe vaccine-related grade 3 or 4 adverse events, GVHD exacerbation, or relapse was observed in our cohort. We posit that SARS-CoV-2 mRNA vaccines induce meaningful cellular immunity in patients with isolated B cell deficiency due to CAR-T19 therapy.

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.

Seroma after Simple Mastectomy in Breast Cancer-The Role of CD4+ T Helper Cells and the Evidence as a Possible Specific Immune Process

Seroma development after breast cancer surgery is the most common postoperative complication seen after mastectomy but neither its origin nor its cellular composition is known. To investigate the assumption of immunological significance, one of the first aims of this pilot study is to describe the cellular content of collected seroma fluids and its corresponding serum in patients with simple mastectomy after needle aspiration, as well as the serum of healthy controls. The content of red blood cells (RBC) was measured by haemato-counter analyses, and the lymphocyte identification/quantification was conducted by flow cytometry analyses in seroma fluid (SFl) and the sera of patients (PBp) as well as controls (PBc). Significantly lower numbers of RBCs were measured in SFl. Cytotoxic T cells are significantly reduced in SFl, whereas T helper (Th) cells are significantly enriched compared to PBp. Significantly higher numbers of Th2 cells were found in SFl and PBp compared to PBc. The exact same pattern is seen when analyzing the Th17 subgroup. In conclusion, in contrast to healthy controls, significantly higher Th2 and Th17 cell subgroup-mediated immune responses were measured in seroma formations and were further confirmed in the peripheral blood of breast cancer (including DCIS) patients after simple mastectomy. This could lead to the assumption of a possible immunological cause for the origin of a seroma.

AKT Hyperphosphorylation and T Cell Exhaustion in Down Syndrome

Down syndrome (DS) is associated with increased susceptibility to infections, auto-immunity, immunodeficiency and haematological malignancies. The exact underlying immunological pathophysiology is still unclear. The immunophenotype and clinical characteristics of DS resemble those of Activated PI3K Delta Syndrome (APDS), in which the PI3K/AKT/mTOR pathway is overactivated. We hypothesized that T cell exhaustion and the hyperactivation of the AKT signalling pathway is also present in immune cells of children with DS. In this observational non-interventional cohort study we collected blood samples of children with DS (n=22) and healthy age-matched controls (n=21) for flowcytometric immunophenotyping, phospho-flow AKT analysis and exhaustion analysis of T cells. The median age was 5 years (range 1-12y). Total T and NK cells were similar for both groups, but absolute values and transitional B cells, naive memory B cells and naive CD4+ and CD8+ T cells were lower in DS. pAKT and AKT were increased for CD3+ and CD4+ T cells and CD20+ B cells in children with DS. Total AKT was also increased in CD8+ T cells. Children with DS showed increased expression of inhibitory markers Programmed cell dealth-1 (PD-1), CD244 and CD160 on CD8+ T cells and increased PD-1 and CD244+ expression on CD4+ T cells, suggesting T cell exhaustion. Children with DS show increased pAKT and AKT and increased T cell exhaustion, which might contribute to their increased susceptibility to infections, auto immunity and haematological malignancies.

Extremely low frequency electromagnetic fields exposure during the prenatal and postnatal periods alters pro-inflammatory cytokines levels by gender

Maternal exposure to the excessive electromagnetic fields is considered harmful to infants and associated with several health problems in life, such as neurological or immune diseases. In this present study we aimed to investigate the potential effects of extremely low-frequency electromagnetic field (ELF-EMF) exposure during the gestational and lactational period of dams on immune system parameters. The development of white blood cells (WBC), lymphocyte subpopulations (CD4⁺ T cells, CD8⁺ T cells, Natural Killer (NK) cells, and B cells) and production of T cell related cytokines were explored in the offsprings. Significant changes were found in WBC and lymphocyte counts. Although no changes in lymphocyte subunits were observed among groups, CD4⁺ cells were significantly increased in the female group exposed to ELF-EMF. Also, IL-17A and IFN-γ levels increased in plasma and spleen. The mean IL-4 level and the expression level of the IL-4 gene were not changed, in the experimental groups. But the expression of the IL-17A gene was also upregulated, which supports cytokine quantification analyses. In conclusion, ELF-EMF exposure in the prenatal and postnatal period increases the level of IL-17A in the spleen and blood of young female rats, and it upregulates IL-17 gene expression in the spleen, resulting in CD4⁺ cell proliferation and inflammation.

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.

Childhood-Onset Movement Disorders Can Mask a Primary Immunodeficiency: 6 Cases of Classical Ataxia-Telangiectasia and Variant Forms

Ataxia-telangiectasia (A-T) is a neurodegenerative and primary immunodeficiency disorder (PID) characterized by cerebellar ataxia, oculocutaneous telangiectasia, immunodeficiency, progressive respiratory failure, and an increased risk of malignancies. It demands specialized care tailored to the individual patient’s needs. Besides the classical ataxia-telangiectasia (classical A-T) phenotype, a variant phenotype (variant A-T) exists with partly overlapping but some distinctive disease characteristics. Here we present a case series of 6 patients with classical A-T and variant A-T, which illustrates the phenotypic variability of A-T that can present in childhood with prominent extrapyramidal features, with or without cerebellar ataxia. We report the clinical data, together with a detailed genotype description, immunological analyses, and related expression of the ATM protein. We show that the presence of some residual ATM kinase activity leads to the clinical phenotype variant A-T that differs from the classical A-T. Our data illustrate that the diagnosis of the variant form of A-T can be delayed and difficult, while early recognition of the variant form as well as the classical A-T is a prerequisite for providing a correct prognosis and appropriate rehabilitation and support, including the avoidance of diagnostic X-ray procedures, given the increased risk of malignancies and the higher risk for side effects of subsequent cancer treatment.

Infection in the Developing Brain: The Role of Unique Systemic Immune Vulnerabilities

Central nervous system (CNS) infections remain a major burden of pediatric disease associated with significant long-term morbidity due to injury to the developing brain. Children are susceptible to various etiologies of CNS infection partly because of vulnerabilities in their peripheral immune system. Young children are known to have reduced numbers and functionality of innate and adaptive immune cells, poorer production of immune mediators, impaired responses to inflammatory stimuli and depressed antibody activity in comparison to adults. This has implications not only for their response to pathogen invasion, but also for the development of appropriate vaccines and vaccination strategies. Further, pediatric immune characteristics evolve across the span of childhood into adolescence as their broader physiological and hormonal landscape develop. In addition to intrinsic vulnerabilities, children are subject to external factors that impact their susceptibility to infections, including maternal immunity and exposure, and nutrition. In this review we summarize the current evidence for immune characteristics across childhood that render children at risk for CNS infection and introduce the link with the CNS through the modulatory role that the brain has on the immune response. This manuscript lays the foundation from which we explore the specifics of infection and inflammation within the CNS and the consequences to the maturing brain in part two of this review series.

Age and Primary Vaccination Background Influence the Plasma Cell Response to Pertussis Booster Vaccination

Pertussis is a vaccine-preventable disease caused by the bacterium Bordetella pertussis. Over the past years, the incidence and mortality of pertussis increased significantly. A possible cause is the switch from whole-cell to acellular pertussis vaccines, although other factors may also contribute. Here, we applied high-dimensional flow cytometry to investigate changes in B cells in individuals of different ages and distinct priming backgrounds upon administration of an acellular pertussis booster vaccine. Participants were divided over four age cohorts. We compared longitudinal kinetics within each cohort and between the different cohorts. Changes in the B-cell compartment were correlated to numbers of vaccine-specific B- and plasma cells and serum Ig levels. Expansion and maturation of plasma cells 7 days postvaccination was the most prominent cellular change in all age groups and was most pronounced for more mature IgG1+ plasma cells. Plasma cell responses were stronger in individuals primed with whole-cell vaccine than in individuals primed with acellular vaccine. Moreover, IgG1+ and IgA1+ plasma cell expansion correlated with FHA-, Prn-, or PT- specific serum IgG or IgA levels. Our study indicates plasma cells as a potential early cellular marker of an immune response and contributes to understanding differences in immune responses between age groups and primary vaccination backgrounds.

Flow Cytometry Confirmation Post Newborn Screening for SCID in England

An evaluation program for newborn screening for Severe Combined Immunodeficiency began in England in September 2021 based on TREC analysis. Flow cytometry is being used as the follow up diagnostic test for patients with low/absent TRECS. The immunology laboratories have established a protocol and values for diagnosing SCID, other T lymphopenias and identifying healthy babies. This commentary describes the flow cytometry approach used in England to define SCID, T lymphopenia and normal infants after a low TREC result. It provides background to the flow cytometry assays being used and discusses the need to monitor and potentially change these values over time.

Case Report: First Occurrence of Plasmablastic Lymphoma in Activated Phosphoinositide 3-Kinase δ Syndrome

Activated phosphoinositide 3-kinase δ syndrome (APDS) is an autosomal dominant primary immunodeficiency caused by acquired gene function mutation (GOF). APDS has a variety of clinical phenotypes, particularly recurrent respiratory infections and lymphoproliferation. Here we report a pediatric patient with APDS who presented with recurrent respiratory infections, lymphoproliferation, hepatosplenomegaly, bronchoscopy suggesting numerous nodular protrusions in the airways and a decrease in both T and B lymphocytes, and progression to plasmablastic lymphoma (PBL) after 1 year. Whole exome sequencing revealed a heterozygous mutation in the PIK3CD gene (c.3061 G>A p.E1021K). This is the first reported case of APDS combined with PBL and pediatricians should follow up patients with APDS regularly to be alert for secondary tumours.

Are HIV-1-Specific Antibody Levels Potentially Useful Laboratory Markers to Estimate HIV Reservoir Size? A Review

Despite the benefits achieved by the widespread availability of modern antiretroviral therapy (ART), HIV RNA integration into the host cell genome is responsible for the creation of latent HIV reservoirs, and represents a significant impediment to completely eliminating HIV infection in a patient via modern ART alone. Several methods to measure HIV reservoir size exist; however, simpler, cheaper, and faster tools are required in the quest for total HIV cure. Over the past few years, measurement of HIV-specific antibodies has evolved into a promising option for measuring HIV reservoir size, as they can be measured via simple, well-known techniques such as the western blot and enzyme-linked immunosorbent assay (ELISA). In this article, we re-visit the dynamic evolution of HIV-1-specific antibodies and the factors that may influence their levels in the circulation of HIV-positive individuals. Then, we describe the currently-known relationship between HIV-1-specific antibodies and HIV reservoir size based on study of data from contemporary literature published during the past 5 years. We conclude by highlighting current trends, and discussing the individual HIV-specific antibody that is likely to be the most reliable antibody for potential future utilization for quantification of HIV reservoir size.

Reticular Dysgenesis: A Rare Immunodeficiency in a Neonate With Cytopenias and Bacterial Sepsis

Severe combined immunodeficiency (SCID) consists of a group of disorders defined by abnormal B and T cell development that typically results in death within the first year of life if undiagnosed or untreated. Reticular dysgenesis (RD) is a rare but especially severe form of SCID that is caused by adenylate kinase 2 deficiency and is characterized not only by lymphopenia but also by profound neutropenia. RD predisposes patients to viral and fungal infections typical of SCID as well as serious bacterial infections atypical in the neonatal period in other SCID types. RD is also associated with sensorineural hearing loss not typically seen in other forms of SCID. Without rapid diagnosis and curative hematopoietic stem cell transplantation, RD is fatal within days to months due to overwhelming bacterial infection. The inclusion of the T cell receptor excision circle assay nationally in 2017 on the newborn screen has facilitated diagnosis of SCID in the neonatal period. This case reports on a male infant with RD who presented after preterm birth with severe cytopenias and a gastrointestinal anomaly and ultimately developed severe bacterial sepsis. Postmortem bone marrow evaluation and panel-based gene sequencing identifying 2 novel variants in the adenylate kinase 2 gene provided confirmation for a diagnosis of RD. This case emphasizes the importance of thorough diagnostic evaluation, including the newborn screen, in neonates and infants with persistent and unexplained cytopenias. Prompt hematology and/or immunology referral is advised for disease management and to facilitate hematopoietic stem cell transplantation to optimize long-term survival.

The immune landscape of SARS-CoV-2-associated Multisystem Inflammatory Syndrome in Children (MIS-C) from acute disease to recovery

Multisystem inflammatory syndrome in children (MIS-C) is a life-threatening disease occurring several weeks after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Deep immune profiling showed acute MIS-C patients had highly activated neutrophils, classical monocytes and memory CD8+ T-cells, with increased frequencies of B-cell plasmablasts and double-negative B-cells. Post treatment samples from the same patients, taken during symptom resolution, identified recovery-associated immune features including increased monocyte CD163 levels, emergence of a new population of immature neutrophils and, in some patients, transiently increased plasma arginase. Plasma profiling identified multiple features shared by MIS-C, Kawasaki Disease and COVID-19 and that therapeutic inhibition of IL-6 may be preferable to IL-1 or TNF-α. We identified several potential mechanisms of action for IVIG, the most commonly used drug to treat MIS-C. Finally, we showed systemic complement activation with high plasma C5b-9 levels is common in MIS-C suggesting complement inhibitors could be used to treat the disease.

A Critical Review on the Standardization and Quality Assessment of Nonfunctional Laboratory Tests Frequently Used to Identify Inborn Errors of Immunity

Inborn errors of immunity (IEI), which were previously termed primary immunodeficiency diseases, represent a large and growing heterogeneous group of diseases that are mostly monogenic. In addition to increased susceptibility to infections, other clinical phenotypes have recently been associated with IEI, such as autoimmune disorders, severe allergies, autoinflammatory disorders, benign lymphoproliferative diseases, and malignant manifestations. The IUIS 2019 classification comprises 430 distinct defects that, although rare individually, represent a group affecting a significant number of patients, with an overall prevalence of 1:1,200-2,000 in the general population. Early IEI diagnosis is critical for appropriate therapy and genetic counseling, however, this process is deeply dependent on accurate laboratory tests. Despite the striking importance of laboratory data for clinical immunologists, several IEI-relevant immunoassays still lack standardization, including standardized protocols, reference materials, and external quality assessment programs. Moreover, well-established reference values mostly remain to be determined, especially for early ages, when the most severe conditions manifest and diagnosis is critical for patient survival. In this article, we intend to approach the issue of standardization and quality control of the nonfunctional diagnostic tests used for IEI, focusing on those frequently utilized in clinical practice. Herein, we will focus on discussing the issues of nonfunctional immunoassays (flow cytometry, enzyme-linked immunosorbent assays, and turbidimetry/nephelometry, among others), as defined by the pure quantification of proteins or cell subsets without cell activation or cell culture-based methods.

Multivariate Analysis of Immune Reconstitution and Relapse Risk Scoring in Children Receiving Allogeneic Stem Cell Transplantation for Acute Leukemias

A timely and effective immune reconstitution after hematopoietic stem cell transplantation (HSCT) is of crucial importance to enhance graft-versus-leukemia reaction in hematological malignancies. Several factors can influence the yield of this process, and new mathematical models are needed to describe this complex phenomenon.

Age-stratified pediatric reference values of lymphocytes in the Moroccan population

The number of circulating lymphocytes is altered in a number of diseases including either increase (lymphocytosis) or decrease (lymphocytopenia). Therefore, the assessment of total blood lymphocyte numbers and the relative distribution of lymphocyte subsets is a critical front-line tool in the clinical diagnosis of a number of diseases, including pediatric diseases and disorders. However, the interpretation of this data requires comparison of patient's results to reliable reference values. Blood lymphocyte subpopulation numbers are also subject to genetic polymorphisms, immunogenic and environmental factors and vary greatly between populations. While the best practice reference values should be established within local representative populations of healthy subjects, to date, Caucasian reference values are used in Morocco due to the absence of indigenous reference values. Potential differences in blood lymphocyte subpopulation reference values between Caucasian versus Moroccan populations can adversely affect the diagnosis of pediatric and childhood diseases and disorders such as primary immunodeficiency (PID) in Morocco.

OBJECTIVE

The aim of this study was to establish the age-stratified normal reference values of blood lymphocyte subsets for the pediatric Moroccan population.

METHODS

We measured the concentration of lymphocyte subpopulations by flow cytometry from 83 Moroccan healthy subjects stratified into 5 age groups of 0-1, 1-2, 2-6, 6-12 and > 12-18 (adult).

RESULTS

The absolute and relative amounts of the main lymphocyte subsets of T-cells, B cells and Natural Killer (NK) cells were measured and compared to previously described reference values from Cameroonian, Turkish, American and Dutch populations. Additionally, we also observed an age-related decline in the absolute population sizes of lymphocyte subsets within our study group. Relative proportions of CD3+CD4+ helper T lymphocytes decreased with increasing age and by 12 years-adult age, both proportions of CD3+CD4+ helper T lymphocytes and CD3+CD8+ cytotoxic T lymphocytes, as well as CD3-CD19+ B lymphocytes were also decreased. Finally, we compared the median values and range of our Moroccan study group with that of published results from Cameroon, Turkey, USA and Netherlands and observed significant differences in median and mean values of absolute number and relative proportions of lymphocyte subsets especially at 0-1 years and 1-2 years age groups. Above age 12 years, the Moroccan values were lower. For NK cells, the Moroccan values are also lower.

CONCLUSIONS

The results of this study have a significant impact in improving the threshold values of the references intervals routinely used in the diagnosis of paediatric diseases such as PIDs or mother-to-child transmitted HIV within the Moroccan population.

Hematopoietic stem cell transplantation in a patient with proteasome-associated autoinflammatory syndrome (PRAAS)

BACKGROUND

Proteasome-associated autoinflammatory syndromes (PRAASs) form a family of recently described rare autosomal recessive disorders of disturbed proteasome assembly and proteolytic activity caused by mutations in genes coding for proteasome subunits. The treatment options for these proteasome disorders consist of lifelong immunosuppressive drugs or Janus kinase inhibitors, which may have partial efficacy and noticeable side effects. Because proteasomes are ubiquitously expressed, it is unknown whether hematopoietic stem cell transplantation (HSCT) may be a sufficient treatment option.

OBJECTIVE

Our aim was to report the case of a young boy with a treatment-resistant cutaneous vasculitis that was initially suspected to be associated with a gene variant in SH2D1A.

METHODS

Whole-exome sequencing was performed to identify the genetic defect. Molecular and functional analyses were performed to assess the impact of variants on proteasomal function. The immune characterization led to the decision to perform HSCT on our patient and conduct follow-up over the 7-year period after the transplant. Because loss of myeloid chimerism after the first HSCT was associated with relapse of autoinflammation, a second HSCT was performed.

RESULTS

After the successful second HSCT, the patient developed mild symptoms of lipodystrophy, which raised the suspicion of a PRAAS. Genetic analysis revealed 2 novel heterozygous variants in PSMB4 (encoding proteasomal subunit β7). Retrospective analysis of patient cells stored before the first HSCT and patient cells obtained after the second HSCT demonstrated that HSCT successfully rescued proteasome function, restored protein homeostasis, and resolved the interferon-stimulated gene signature. Furthermore, successful HSCT alleviated the autoinflammatory manifestations in our patient.

CONCLUSION

Patients with treatment-resistant PRAAS can be cured by HSCT.

T cell composition and polygenic multiple sclerosis risk: A population-based study in children

Background and purpose

Patients with multiple sclerosis (MS) have altered T cell function and composition. Common genetic risk variants for MS affect proteins that function in the immune system. It is currently unclear to what extent T cell composition is affected by genetic risk factors for MS, and how this may precede a possible disease onset. Here, we aim to assess whether an MS polygenic risk score (PRS) is associated with an altered T cell composition in a large cohort of children from the general population.

Methods

We included genotyped participants from the population‐based Generation R study in whom immunophenotyping of blood T cells was performed at the age of 6 years. Analyses of variance were used to determine the impact of MS‐PRSs on total T cell numbers (n = 1261), CD4⁺ and CD8⁺ lineages, and subsets therein (n= 675). In addition, T‐cell‐specific PRSs were constructed based on functional pathway data.

Results

The MS‐PRS negatively correlated with CD8⁺ T cell frequencies (p = 2.92 × 10⁻³), which resulted in a positive association with CD4⁺/CD8⁺ T cell ratios (p = 8.27 × 10⁻⁹). These associations were mainly driven by two of 195 genome‐wide significant MS risk variants: the main genetic risk variant for MS, HLA‐DRB1*15:01 and an HLA‐B risk variant. We observed no significant associations for the T‐cell‐specific PRSs.

Conclusions

Our results suggest that MS‐associated genetic variants affect T cell composition during childhood in the general population.

Thymic Epithelial Cell Alterations and Defective Thymopoiesis Lead to Central and Peripheral Tolerance Perturbation in MHCII Deficiency

Major Histocompatibility Complex (MHC) class II (MHCII) deficiency (MHCII-D), also known as Bare Lymphocyte Syndrome (BLS), is a rare combined immunodeficiency due to mutations in genes regulating expression of MHCII molecules. MHCII deficiency results in impaired cellular and humoral immune responses, leading to severe infections and autoimmunity. Abnormal cross-talk with developing T cells due to the absence of MHCII expression likely leads to defects in thymic epithelial cells (TEC). However, the contribution of TEC alterations to the pathogenesis of this primary immunodeficiency has not been well characterized to date, in particular in regard to immune dysregulation. To this aim, we have performed an in-depth cellular and molecular characterization of TEC in this disease. We observed an overall perturbation of thymic structure and function in both MHCII-/- mice and patients. Transcriptomic and proteomic profiling of murine TEC revealed several alterations. In particular, we demonstrated that impairment of lymphostromal cross-talk in the thymus of MHCII-/- mice affects mTEC maturation and promiscuous gene expression and causes defects of central tolerance. Furthermore, we observed peripheral tolerance impairment, likely due to defective Treg cell generation and/or function and B cell tolerance breakdown. Overall, our findings reveal disease-specific TEC defects resulting in perturbation of central tolerance and limiting the potential benefits of hematopoietic stem cell transplantation in MHCII deficiency.

Blinatumomab in Pediatric Acute Lymphoblastic Leukemia-From Salvage to First Line Therapy (A Systematic Review)

Acute lymphoblastic leukemia is by far the most common malignancy in children, and new immunotherapeutic approaches will clearly change the way we treat our patients in future years. Blinatumomab is a bispecific T-cell-engaging antibody indicated for the treatment of relapsed/refractory acute lymphoblastic leukemia (R/R-ALL). The use of blinatumomab in R/R ALL has shown promising effects, especially as a bridging tool to hematopoietic stem cell transplantation. For heavily pretreated patients, the response to one or two cycles of blinatumomab ranges from 34% to 66%. Two randomized controlled trials have very recently demonstrated an improved reduction in minimal residual disease as well as an increased survival for patients treated with blinatumomab compared to standard consolidation treatment in first relapse. Current trials using blinatumomab frontline for high-risk patients or as a consolidation treatment post-transplant will show whether efficacy is even higher in less heavily pretreated patients. Due to the distinct pattern of adverse events compared to high-dose conventional chemotherapy, blinatumomab could play an important role for patients with a risk for severe chemotherapy-associated toxicities. This systematic review discusses all published results for blinatumomab in children as well as all ongoing clinical trials.

Time-related variation in IgG subclass concentrations in a group of healthy Danish adults

Introduction

Immunoglobulin G subclass measurements are important for the diagnostic work‐up of immunodeficiencies and immunoglobulin G4 (IgG4) related diseases. It is currently unknown whether a single sampling is truly representative for an individual's IgG subclass concentrations. This study aimed to investigate whether IgG and IgG subclass concentrations in healthy individuals are stable over time.

Method

With a span of median 42 weeks, four samples from each of 54 (34M, 20F) healthy adult volunteers (24–66 years) were analyzed for IgG and IgG1–4 using turbidimetry. Concentrations were compared within and between individuals.

Results

IgG and IgG subclass concentrations followed either a normal (IgG, IgG1, and IgG3) or log normal (IgG2 and IgG4) distribution. Immunoglobulin 4 demonstrated by far the widest range of concentrations between individuals (670‐fold: 0.004–2.68 g/L). Immunoglobulin G subclass variations within individuals were expressed as pooled standard deviations (PSD). These ranged from 0.056 (IgG4) to 0.955 g/L (IgG) and correlated with mean concentration of IgG or the particular IgG subclass. As a consequence, the relative PSDs (i.e., PSD divided by mean IgG or IgG subclass concentration) fell within a narrow range: 5.82%–10.1%. Based on these numbers, the 95%‐upper one‐sided confidence limits for intraindividual IgG and IgG subclass variation was calculated to range from 9.82% (IgG2) to 16.9% (IgG4).

Conclusion

The study documents that IgG or IgG subclass concentrations within healthy individuals are very stable over at least 42 weeks. The expected variation for IgG4 concentrations at a 95% confidence level does not exceed ±16.9%.