Activation-induced cytidine deaminase (AID) is a 'master molecule' in immunoglobulin (Ig) class-switch recombination (CSR) and somatic hypermutation (SHM) generation, AID deficiencies are associated with hyper-IgM phenotypes in humans and mice. We show here that recessive mutations of the gene encoding uracil-DNA glycosylase (UNG) are associated with profound impairment in CSR at a DNA precleavage step and with a partial disturbance of the SHM pattern in three patients with hyper-IgM syndrome. Together with the finding that nuclear UNG expression was induced in activated B cells, these data support a model of CSR and SHM in which AID deaminates cytosine into uracil in targeted DNA (immunoglobulin switch or variable regions), followed by uracil removal by UNG.

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The gastrointestinal tract contains the largest lymphoid organ to react with pathogenic microorganisms and suppress excess inflammation. Patients with primary immunodeficiency diseases (PIDs) can suffer from refractory diarrhea. In this study, we present two siblings who began to suffer from refractory diarrhea with a poor response to aggressive antibiotic and immunosuppressive treatment after surgical release of neonatal intestinal obstruction. Their lymphocyte proliferation was low, but superoxide production and IL-10 signaling were normal. Candidate genetic approach targeted to genes involved in PIDs with inflammatory bowel disease (IBD)-like manifestation was unrevealing. Whole-genome sequencing revealed novel heterozygous mutations Glu75Lys and nucleotide 520–521 CT deletion in the tetratricopeptide repeat domain 7A (TTC7A) gene. A Medline search identified 49 patients with TTC7A mutations, of whom 20 survived. Their phenotypes included both multiple intestinal atresia (MIA) and combined T and/or B immunodeficiency (CID) in 16, both IBD and CID in 14, isolated MIA in 8, MIA, IBD, and CID complex in 8, and isolated IBD in 3. Of these 98 mutant alleles over-through the coding region clustering on exon 2 (40 alleles), exon 7 (12 alleles), and exon 20 (10 alleles), 2 common hotspot mutations were c.211 G>A (p.E71K in exon 2) in 26 alleles and AAGT deletion in exon 7 (+3) in 10 alleles. Kaplan–Meier analysis showed that those with biallelic missense mutations (p = 0.0168), unaffected tetratricopeptide repeat domains (p = 0.0311), and developing autoimmune disorders (p = 0.001) had a relatively better prognosis. Hematopoietic stem cell transplantation (HSCT) restored immunity and seemed to decrease the frequency of infections; however, refractory diarrhea persisted. Clinical improvement was reported upon intestinal and liver transplantation in a child with CID and MIA of unknown genetic etiology. In conclusion, patients with TTC7A mutations presenting with the very early onset of refractory diarrhea had limit improvement by HSCT or/and tailored immunosuppressive therapy in the absence of suitable intestine donors. We suggest that MIA–CID–IBD disorder caused by TTC7A mutations should also be included in the PID classification of “immunodeficiencies affecting cellular and humoral immunity” to allow for prompt recognition and optimal treatment.

Natural human immunity to the mycobacteria group, including Mycobacterium tuberculosis, Bacille Calmette-Guérin (BCG) or nontuberculous mycobacteria (NTM), and/or Salmonella species, relies on the functional IL-12/23-IFN-γ integrity of macrophages (monocyte/dendritic cell) connecting to T lymphocyte/NK cells. Patients with severe forms of primary immunodeficiency diseases (PIDs) have more profound immune defects involving this impaired circuit in patients with severe combined immunodeficiencies (SCID) including complete DiGeorge syndrome, X-linked hyper IgM syndrome (HIGM) (CD40L mutation), CD40 deficiency, immunodeficiency with or without anhidrotic ectodermal dysplasia (NEMO and IKBA mutations), chronic granulomatous disease (CGD) and hyper IgE recurrent infection syndromes (HIES). The patients with severe PIDs have broader diverse infections rather than mycobacterial infections. In contrast, patients with an isolated inborn error of the IL-12/23-IFN-γ pathway are exclusively prone to low-virulence mycobacterial infections and nontyphoid salmonella infections, known as Mendelian susceptibility to the mycobacterial disease (MSMD) phenotype. Restricted defective molecules in the circuit, including IFN-γR1, IFN-γR2, IL-12p40, IL-12R-β1, STAT-1, NEMO, IKBA and the recently discovered CYBB responsible for autophagocytic vacuole and proteolysis, and interferon regulatory factor 8 (IRF8) for dendritic cell immunodeficiency, have been identified in around 60% of patients with the MSMD phenotype. Among all of the patients with PIDs referred for investigation since 1985, we have identified four cases with the specific defect (IFNRG1 for three and IL12RB for one), presenting as both BCG-induced diseases and NTM infections, in addition to some patients with SCID, HIGM, CGD and HIES. Furthermore, manifestations in patients with autoantibodies to IFN-γ (autoAbs-IFN-γ), which is categorized as an anticytokine autoantibody syndrome, can resemble the relatively persistent MSMD phenotype lacking BCG-induced diseases.

A study of newborn screening for severe combined immunodeficiency (SCID) by detecting the T-cell receptor excision circle (TRECs) copy number in dried blood spots (DBSs) collected from newborns 3 days of age began in 2010 in Taiwan, and SCID screening was subsequently implemented country-wide in 2012. A total of 920,398 newborns were screened during a period of 78 months. Of these, 175 newborns (0.02%) were requested to undergo an immune function survey, and 136 cases (1 in 6768 newborns) were ultimately diagnosed as having T cell lymphopenia. The screening detected seven cases of typical SCID, with an incidence of 1 in 131,485 newborns (95% confidence interval, 1/63,693~1/271,434). Hematopoietic stem cell transplantation was performed in six patients before overt infection occurred, and the survival rate was 100%. The screening also detected eight cases of SCID variants and 20 cases of 22q11.2 deletion syndrome. Other etiologies of T lymphopenia were identified, and those newborns were evaluated and managed according to their immunological status. Owing to the introduction of newborn screening by measuring the TREC copy number, early administration of treatments became possible for newborns with conditions that put them at risk of primary or secondary immunodeficiency.

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Patients with defective IL-12/23-IFN-gamma circuit may resemble or overlap CGD manifestations of refractory cutaneous atypical mycobacterial granuloma and salmonella pneumatocele.

correlated with average testing level (r = 0.742, p = 0.002). Cases from medium-HDI countries/regions focused on learning how to investigate a patient for PIDs in cases of severe or atypical infections, whereas those from very-high-HDI countries/regions, from which most faculty members originated, listed hematopoietic stem cell transplantation and gene therapy, newborn screening, and research as learning issues more frequently. Conclusion: There are unique HDI-related PID resource and training needs in each country/region. APSID proposes HDI group-specific strategies to improve PID care and education in her member countries/regions. Further quantitative analysis of needs in PID care in Asia Pacific is needed for lobbying governments to increase their support for PID care and research.