Background The number of inherited diseases and the spectrum of clinical manifestations of primary immunodeficiency disorders (PIDs) are ever-expanding. Molecular diagnosis using genomic approaches should be performed for all PID patients since it provides a resource to improve the management and to estimate the prognosis of patients with these rare immune disorders. Method The current update of Iranian PID registry (IPIDR) contains the clinical phenotype of newly registered patients during last 5 years (2013-2018) and the result of molecular diagnosis in patients enrolled for targeted and nextgeneration sequencing. Results Considering the newly diagnosed patients (n = 1395), the total number of registered PID patients reached 3056 (1852 male and 1204 female) from 31 medical centers. The predominantly antibody deficiency was the most common subcategory of PID (29.5%). The putative causative genetic defect was identified in 1014 patients (33.1%) and an autosomal recessive pattern was found in 79.3% of these patients. Among the genetically different categories of PID patients, the diagnostic rate was highest in defects in immune dysregulation and lowest in predominantly antibody deficiencies and mutations in the MEFV gene were the most frequent genetic disorder in our cohort.

This study provides proof of principle for the application of targeted next-generation sequencing panels in countries with limited diagnostic resources. The effect of genetic diagnosis on clinical care requires continued improvements in therapeutic resources for these patients.

The molecular basis of interindividual clinical variability upon infection with Staphylococcus aureus is unclear. We describe patients with haploinsufficiency for the linear deubiquitinase OTULIN, encoded by a gene on chromosome 5p. Patients present episodes of life-threatening necrosis, typically triggered by S. aureus infection. The disorder is phenocopied in patients with the 5p- (Cri-du-Chat) chromosomal deletion syndrome. OTULIN haploinsufficiency causes an accumulation of linear ubiquitin in dermal fibroblasts, but TNF-receptor NF-κB-signaling remains intact. Blood leukocyte subsets are unaffected. The OTULIN-dependent accumulation of caveolin-1 in dermal fibroblasts—but not leukocytes—facilitates the cytotoxic damage inflicted by the staphylococcal virulence factor α-toxin. Naturally elicited antibodies against α-toxin contribute to incomplete clinical penetrance. Human OTULIN haploinsufficiency underlies life-threatening staphylococcal disease by disrupting cell-intrinsic immunity to α-toxin in non-leukocytic cells.

The IL12RB1 locus is Alu-enriched and therefore prone to rearrangements at various positions. CNVs should be considered in the genetic diagnosis of IL-12Rβ1 deficiency.

The C-type lectin langerin/CD207 was originally discovered as a specific marker for epidermal Langerhans cells (LC). Recently, additional and distinct subsets of langerin+ dendritic cells (DC) have been identified in lymph nodes and peripheral tissues of mice. Although the role of LC for immune activation or modulation is now being discussed controversially, other langerin+ DC appear crucial for protective immunity in a growing set of infection and vaccination models. In knock-in mice that express the human diphtheria toxin receptor under control of the langerin promoter, injection of diphtheria toxin ablates LC for several weeks whereas other langerin+ DC subsets are replenished within just a few days. Thus, by careful timing of diphtheria toxin injections selective states of deficiency in either LC only or all langerin+ cells can be established. Taking advantage of this system, we found that, unlike selective LC deficiency, ablation of all langerin+ DC abrogated the activation of IFN-γ–producing and cytolytic CD8+ T cells after gene gun vaccination. Moreover, we identified migratory langerin+ dermal DC as the subset that directly activated CD8+ T cells in lymph nodes. Langerin+ DC were also critical for IgG1 but not IgG2a Ab induction, suggesting differential polarization of CD4+ T helper cells by langerin+ or langerin-negative DC, respectively. In contrast, protein vaccines administered with various adjuvants induced IgG1 independently of langerin+ DC. Taken together, these findings reflect a highly specialized division of labor between different DC subsets both with respect to Ag encounter as well as downstream processes of immune activation.