Analysis of LRBA pathogenic variants and the association with functional protein domains and clinical presentation.

LRBA is a cytoplasmic protein that is ubiquitously distributed. Almost all LRBA domains have a scaffolding function. In 2012, it was reported that homozygous variants in LRBA are associated with early-onset hypogammaglobulinemia. Since its discovery, more than 100 pathogenic variants have been reported. This review focuses on the variants reported in LRBA and their possible associations with clinical phenotypes. In this work LRBA deficiency cases reported more than 11 years ago have been revised. A database was constructed to analyze the type of variants, age at onset, clinical diagnosis, infections, autoimmune diseases, and cellular and immunoglobulin levels. The review of cases from 2012 to 2023 showed that LRBA deficiency was commonly diagnosed in patients with a clinical diagnosis of Common Variable Immunodeficiency, followed by enteropathy, neonatal diabetes mellitus, ALPS, and X-linked-like syndrome. Most cases show early onset of presentation at <6 years of age. Most cases lack protein expression, whereas hypogammaglobulinemia is observed in half of the cases, and IgG and IgA levels are isotypes reported at low levels. Patients with elevated IgG levels exhibited more than one autoimmune manifestation. Patients carrying pathogenic variants leading to a premature stop codon show a severe phenotype as they have an earlier onset of disease presentation, severe autoimmune manifestations, premature death, and low B cells and regulatory T cell levels. Missense variants were more common in patients with low IgG levels and cytopenia. This work lead to the conclusion that the type of variant in LRBA has association with disease severity, which leads to a premature stop codon being the ones that correlates with severe disease.

Reference values of leukocyte and lymphocytes populations in umbilical cord and capillary blood in healthy Mexican newborns.

INTRODUCTION: In newborns, dramatic changes occur in the blood and bone marrow during the first hours; there are rapid fluctuations in the quantities of leukocytes populations. In this work, we investigated leukocytes subsets counts in two types of blood samples (cord blood and capillary blood) extracted from healthy newborns. METHODS: Blood samples from Mexican neonates were collected by Instituto Nacional de Pediatría with written informed consent. For all samples we determined leukocytes populations; neutrophils, monocytes, total lymphocytes, and populations: T CD3+ cells, TCD4+ cells, T CD8+ cells, B CD19+ cells and NK CD16+56 cells by flow cytometry. We used the Mann-Whitney U test to compare leukocytes of cord and capillary blood; also to analyze the differences between gender and we obtained reference values of the cord and capillary blood in neonates. RESULTS: We observed higher absolute counts and frequencies of total lymphocyte in capillary blood compared with cord blood. In absolute numbers, the capillary blood showed significant differences in neutrophils, monocytes, lymphocytes, T CD3+ cells, T CD4+ cells, T CD8+ cells, B CD19+ cells, and NK cells; no significant differences were observed between genders. DISCUSSION: Our data contribute to newborn Mexican reference values for all these populations of leukocytes. We found that the dispersal range differs between the two types of blood, suggesting a different fate in the immune response. Immunophenotyping of the blood cell population to identify these cells is an essential tool in the diagnosis and follow-up of neonates with immunodeficiencies and other immune disorders.

Expanding the clinical features of autoinflammation and phospholipase Cγ2-associated antibody deficiency and immune dysregulation by description of a novel patient.

BACKGROUND: Autoinflammation and phospholipase Cγ2-associated antibody deficiency and immune dysregulation (APLAID) is an exceedingly rare monogenic autoinflammatory disease. To date, only five cases have been reported with four distinct pathogenic mutations. OBJECTIVES: We present a novel case of APLAID, corroborated by molecular analysis, with newly described clinical findings including central nervous system vasculitis (CNSV); and distinctive histopathological characteristics that may expand our knowledge of this rare disease's phenotype. METHODS: This is a case report presentation of a 3-year-old boy, seen at a reference paediatric hospital in Mexico. His parents authorized the use of his clinical information and photographs. RESULTS: A 3-day-old boy presented to the emergency department with a vesiculo-pustular rash that resolved within 1 week. Two months later, he developed widespread papules and pseudovesicles that evolved into infiltrated plaques. He also had periodical flares of conjunctivitis, diarrhoea and erythematous blistering acral plaques triggered by upper respiratory infections. By the age of 10 months, he experienced seizures and CNSV. Laboratory work-up showed mild neutropenia, decreased serum levels of immunoglobulins and B-cell lymphopenia. A skin biopsy revealed a dense, perivascular and interstitial histiocytic and granulomatous infiltrate, with palisading granulomas, and leucocytoclastic vasculitis with karyorrhexis. APLAID syndrome was confirmed by Sanger sequencing of PLCG2 gene [heterozygous genotype LRG_376t1:c.2543T>C or p.(Leu848Pro)]. CONCLUSIONS: Presence of CNSV has not been previously described in APLAID, however as the number of reported patients with APLAID is very small, it is possible that the overall spectrum of clinical manifestations has not been completely elucidated. The herein identified p.(Leu848Pro) variant was also documented in a Portuguese patient, suggesting that it could be a PLCG2 gene 'hot-spot'.

Low percentages of regulatory T cells in common variable immunodeficiency (CVID) patients with autoimmune diseases and its association with increased numbers of CD4+CD45RO+ T and CD21low B cells.

BACKGROUND: Common variable immunodeficiency (CVID) is a heterogeneous group of primary antibody deficiencies defined by marked reductions in serum IgG, IgA and/or IgM levels and recurrent bacterial infections. Some patients are associated with defects in T cells and regulatory T cells (Tregs), resulting in recurrent viral infections and early-onset autoimmune disease. METHODS: We analyzed whether there is an association between Tregs cells (CD4+CD25+CD127low and CD4+CD25+FoxP3+); memory T cells (CD4+CD45RO+); memory B cells (CD19+CD27-IgD-); and CD21low B cells (CD19+CD38lowCD21low); as well as autoimmune manifestations in 36 patients with CVID (25 women and 11 men, mean age 24 years), all by flow cytometry. RESULTS: Fourteen patients presented with autoimmune diseases (AI) (39%), including 11 with autoimmune thrombocytopenia (ITP) (31%); two with vitiligo (6%); one with systemic lupus erythematosus (LES) (3%); and one with multiple sclerosis (MS) (3%). CVID patients with AI had a reduced proportion of Tregs (both CD4+CD25+CD127low and FoxP3+ cells) compared with healthy controls. CVID patients with AI had expanded CD21low B cell populations compared with patients who did not have AI. A correlation between increased CD4+CD45RO T cell populations and reduced Tregs was also observed. CONCLUSIONS: Our results showed that 39% of patients with CVID had AI and reduced Tregs populations. Research in this area might provide noteworthy data to better understand immune dysfunction and dysregulation related to CVID.

CD38 protein deficiency induces autoimmune characteristics and its activation enhances IL-10 production by regulatory B cells.

CD38 is a transmembrane protein expressed in B lymphocytes, and is able to induce responses as proliferation, differentiation or apoptosis. Several reports propose that CD38 deficiency accelerates autoimmune processes in murine models of autoimmune diabetes, lymphoproliferation and rheumatoid arthritis. Other reports have shown elevated CD38 expression in B and T cells from patients with autoimmunity; however, the role of CD38 is still unclear in the development of autoimmunity. Recently, it has been characterized as CD1dhi CD5+ regulatory B cell subpopulation able to produce IL-10, and the loss of these cells exacerbates the autoimmunity in murine models. Here, we report that CD38-/- mice exhibited elevated titres of ANAS, anti-dsDNA autoantibodies from 12 months of age and were higher by 16 months of age and mice presented kidney damage. Interestingly, there is a reduction in the survival of CD38-/- mice compared to the WT. Furthermore, CD38 is highly expressed by CD1dhigh CD5+ regulatory B cells, and the agonistic anti-CD38 stimulus plus LPS was able to increase the percentage of this cell subset and its ability to induce IL-10 production. Together, these results suggest that CD38 could play a role in the control of autoimmune diseases through their expression on regulatory B cells.

Clinical and mutational features of X-linked agammaglobulinemia in Mexico.

X-linked agammaglobulinemia (XLA) is caused by BTK mutations, patients typically show <2% of peripheral B cells and reduced levels of all immunoglobulins; they suffer from recurrent infections of bacterial origin; however, viral infections, autoimmune-like diseases, and an increased risk of developing gastric cancer are also reported. In this work, we report the BTK mutations and clinical features of 12 patients diagnosed with XLA. Furthermore, a clinical revision is also presented for an additional cohort of previously reported patients with XLA. Four novel mutations were identified, one of these located in the previously reported mutation refractory SH3 domain. Clinical data support previous reports accounting for frequent respiratory, gastrointestinal tract infections and other symptoms such as the occurrence of reactive arthritis in 19.2% of the patients. An equal proportion of patients developed septic arthritis; missense mutations and mutations in SH1, SH2 and PH domains predominated in patients who developed arthritis.

Functional characterization of two new STAT3 mutations associated with hyper-IgE syndrome in a Mexican cohort.

Hyper-IgE syndrome (HIES) is an immunodeficiency disorder that is characterized by distinctive immunologic and non-immunologic manifestations. Although mutations in signal transducer and activator of transcription 3 (STAT3) have been associated with HIES, the exact nature of the relationship is unknown. Here, we characterized the functional activity of STAT3 and its mutations in 11 Mexican patients with autosomal dominant HIES. STAT3 phosphorylation was evaluated by flow cytometry, and in silico analyses were performed to estimate the impact of allelic mutations on the DNA binding and SH2 domains of the STAT3 protein. Electrophoretic mobility shift assays were used to assess whether the STAT3 mutants could bind to the consensus oligonucleotide target in vitro. Two novel mutations [g.58891A>T (Asn395Tyr) and g.59078A>T (Asn425Tyr)] as well as one possible somatic mosaicism were found in several of the patients who bore some remarkable features. However, there were no direct correlations between genotypes and HIES clinical features. STAT3 phosphorylation was found to be lower in the patient cohort than in healthy controls. Moreover, the mutated STAT3 proteins could bind to the Sp1, but not to the STAT3, consensus sequence. From these functional studies, the STAT3 mutations found in our patient cohort were concluded to be deleterious for normal STAT3 function.

Variations of B cell subpopulations in peripheral blood of healthy Mexican population according to age: Relevance for diagnosis of primary immunodeficiencies.

BACKGROUND: Peripheral blood B cells include lymphocytes at various stages of differentiation, each with a specific function in the immune response. All these stages show variations in percentage and absolute number throughout human life. The numbers and proportions of B subpopulation are influenced by factors such as gender, age, ethnicity, and lifestyle. This study establishes reference values according to age of peripheral blood B cell subtypes in healthy Mexican population. METHODS: Peripheral blood from healthy new-borns and adults were analysed for total B cell subpopulations, using surface markers such as CD19, IgM, IgD, CD21, CD24, CD27, and CD38, to identify naïve, memory with and without isotype switch, double-negative, transitional, and plasmablast cells. RESULTS: We observed a significant variation in terms of frequency and absolute counts between all groups analysed. Values from each B cell subpopulation show variations according to age. CONCLUSIONS: In order to attempt to elucidate reference values for B cell subpopulation, the present study evaluated a population sample of healthy blood donors from this region. Values reported here can also be used as a tool for diagnosis of diseases in which B cell maturation is affected.

Lymphocytes and B-cell abnormalities in patients with common variable immunodeficiency (CVID).

BACKGROUND AND AIMS: Common variable immunodeficiency (CVID) is a primary antibody deficiency characterised by decreased antibody production and low or normal B-cell numbers. To elucidate the clinical and immunological heterogeneity of CVID, we studied 16 patients diagnosed with CVID. METHODS: We analysed B, T and NK cell populations. We also assessed CD27 expression to define B-cell subsets and examined the expression of molecules important in B-cell proliferation and differentiation, such as the transmembrane activator and CALM interactor (TACI), inducible costimulator (ICOS), CD154 and CD40. RESULTS: We observed reduced B and T-cell numbers in CVID patients; this reduction was more pronounced in adults. While one group of patients (group I) showed a significant reduction in CD27+ memory B-cells, another group (group II) of patients exhibited numbers of CD27+ memory B-cells similar to the healthy donor. The frequency of B-cells and T-cells expressing CD40 and ICOS, respectively, was significantly lower in all CVID patients compared with healthy donors. Finally, a correlation between the frequency of CD27+ memory B-cells and clinical features was observed in CVID patients. CONCLUSION: These results suggest that in some patients, the combined defects in both T and B-cells may account for CVID. Additionally, patients in group I exhibited an increased frequency of pneumonia and chronic diarrhoea.

Characterization of Bruton's tyrosine kinase mutations in Mexican patients with X-linked agammaglobulinemia.

X-linked agammaglobulinemia (XLA) is a humoral primary immunodeficiency in which affected patients have very low levels of peripheral B cells and a profound deficiency of all immunoglobulin isotypes. Mutations in the gene encoding for Bruton's tyrosine kinase (Btk) are responsible for most of the agammaglobulinemia. In this work, 14 Btk mutations responsible of causing XLA are described; eight of which are novel and six are mutations previously reported. Seven of the mutations were due to deletions and insertions of exons and introns, respectively, which suggest splicing defects. The others were missense mutations, five of which affect arginine residues and have been described, and two new which affect leucine and glutamine residues (L111P and E605G). Most of these mutations were located at the kinase domain of Btk and, less frequently, they were found in PH and SH2 domains. Protein expression was also affected since most of the patients did not express or express very low Btk.