Inborn errors of immunity include multiple genetic abnormalities affecting different components of the innate and adaptive immune systems. More than 450 genes have been described so far including DNA repair defects which may result in predisposition to infections, but also malignancies, neurologic abnormalities and growth retardation. The group of patients with DNA repair and methylation defects exhibit impaired adaptive immunity, which increases susceptibility to infections due to impaired repertoire diversity. In this context, we aimed to investigate the TCRvβ repertoire and its interaction with clinical entities in a group of IEI patients with DNA repair defects including ATM, DCLRE1C, DNA-PRKDC, DNA ligase-4, and BLM. Thirty-nine patients with evidence of DNA repair defects and radiosensitivity and 15 age-matched healthy controls were included in this study. Peripheral lymphocyte subset and TCR-vβ repertoire analyses were performed by flow cytometry. To contrast TCR-repertoire in patients with DNA repair defects to healthy controls, we extracted data on lymphocyte phenotype, thymic function, immunoglobulins, and analysis of the TCRvβ repertoire from a prior study. The entire TCR-vβ repertoire was detected in all patients. However, compared with the control group, 9 of 24 clones (37.5%) were statistically significantly lower, whereas only 3 clones had high levels (p < 0.05). In addition, 62.5% of all clones had lower values than the control group. Some unique vβ clones have been associated with some clinical entities. Clonotypes associated with infections, autoimmunity and lymphoid proliferation were detected in the patient group. Lower TCR-vβ-9 and TCR-vβ23, higher TCR-vβ7.2 were detected in the patients with pneumonia (n = 13) (respectively p = 0.018, p = 0.044 p = 0.032). In addition, AT patients with pneumonia (n = 10) had a lower TCR-vβ-9 clone than patients without pneumonia (n = 25) (p = 0.008). In summary, we observed skewed clonal proliferation of most TCR-vβ clones in DNA repair defects, especially AT. In addition, our study demonstrated that some TCR-vβ clones might be predictive of some clinical entities. To further investigate the impact of the diversity of the TCR repertoire on the clinical phenotype, future studies should focus on the analysis of naïve and memory T cells, the detection of the source of oligoclonality, and the relationship between clonality and clinical entities.

Background Purine nucleoside phosphorylase (PNP) deficiency is a rare autosomal recessive combined immunodeficiency. The phenotype is profound T-cell deficiency with variable B- and NK-cell functions and results in recurrent and persistent infections that typically begin in the first year of life. Neurologic findings occur in approximately two-thirds of patients. The mechanism of neurologic abnormalities is unclear. Hematopoietic stem cell transplantation (HSCT) is the only curative treatment for PNP deficiency. Methods We report here six patients from five unrelated families with PNP deficiency treated in two centers in Turkey. We evaluated the neurological status of patients and compared to post-transplantation period if available. Then we performed PubMed, Google Scholar, and Researchgate searches using the terms "PNP" and "hematopoietic stem cell transplantation" to find all reported cases of PNP transplantation and compared to our cohort. Results Six patients were treated in two centers in Turkey. One patient died from post-transplant complications. The other four patients underwent successful HSCT with good immune reconstitution after transplantation (follow-up 21–48 months) and good neurological outcomes. The other patient with a new mutation is still waiting for a matching HLA donor. Discussion In PNP deficiency, clinical manifestations are variable, and this disease should be considered in the presence of many different clinical findings. Despite the comorbidities that occurred before transplantation, HSCT currently appears to be the only treatment option for this disease. HSCT not only cures immunologic disorders, but probably also improves or at least stabilizes the neurologic status of patients.