Temporally uncoupled signal and coding joint formation in human V(D)J recombination

Leaky Artemis Deficiency and EBV-Related Lymphoproliferative Disease: A Novel Case and Review of the Literature

Introduction

Artemis (DCLRE1C) deficiency causes radiosensitive severe combined immunodeficiency (SCID), although hypomorphic cases can manifest later-onset immunodeficiency, autoimmunity, or lymphoproliferation. We report a 45-year-old man with humoral immunodeficiency, opportunistic infections, and recurrent EBV-positive diffuse large B-cell lymphoma (DLBCL).

Methods

Genetic analysis was performed to identify mutations in the DCLRE1C gene. Functional studies, including γH2AX assays to assess DNA damage repair and measurement of Type I interferon responses, were conducted to evaluate the impact of the variant. A literature review was performed to contextualize the findings.

Results

Biallelic p.Leu70del frameshift mutation in DCLRE1C was identified, leading to significantly decreased mutant protein expression. Functional testing confirmed impaired DNA damage repair, via γH2AX measurement, and elevated Type I interferon responses, indicating cytosolic DNA damage accumulation. A literature review highlighted EBV-positive lymphomas in leaky Artemis deficiency with high mortality rate.

Conclusion

Our report adds hypomorphic DCLRE1C deficiency as an inborn error of immunity that predisposes to EBV-associated lymphoproliferative disease.

Trial Registration

The authors have confirmed clinical trial registration is not needed for this submission.

The multifaceted functions of DNA-PKcs: implications for the therapy of human diseases

The DNA-dependent protein kinase (DNA-PK), catalytic subunit, also known as DNA-PKcs, is complexed with the heterodimer Ku70/Ku80 to form DNA-PK holoenzyme, which is well recognized as initiator in the nonhomologous end joining (NHEJ) repair after double strand break (DSB). During NHEJ, DNA-PKcs is essential for both DNA end processing and end joining. Besides its classical function in DSB repair, DNA-PKcs also shows multifaceted functions in various biological activities such as class switch recombination (CSR) and variable (V) diversity (D) joining (J) recombination in B/T lymphocytes development, innate immunity through cGAS-STING pathway, transcription, alternative splicing, and so on, which are dependent on its function in NHEJ or not. Moreover, DNA-PKcs deficiency has been proven to be related with human diseases such as neurological pathogenesis, cancer, immunological disorder, and so on through different mechanisms. Therefore, it is imperative to summarize the latest findings about DNA-PKcs and diseases for better targeting DNA-PKcs, which have shown efficacy in cancer treatment in preclinical models. Here, we discuss the multifaceted roles of DNA-PKcs in human diseases, meanwhile, we discuss the progresses of DNA-PKcs inhibitors and their potential in clinical trials. The most updated review about DNA-PKcs will hopefully provide insights and ideas to understand DNA-PKcs associated diseases.

A novel digital PCR-based method to quantify (switched) B cells reveals the extent of allelic involvement in different recombination processes in the IGH locus

B cells fulfill an important role in the adaptive immunity. Upon activation and immunoglobulin (IG) class switching, these cells function in the humoral immunity compartment as plasma cells. For clinical applications, it can be important to quantify (switched) B cells accurately in a variety of body fluids and tissues of benign, inflammatory and malignant origin. For decades, flow cytometry and immunohistochemistry (IHC) have been the preferred methods for quantification. Although these methods are widely used, both depend on the accessibility of B cell epitopes and therefore require intact (fixed) cells. Whenever samples are low in quantity and/or quality, accurate quantification can be difficult. By shifting the focus from epitopes to DNA markers, quantification of B cells remains achievable. During differentiation and maturation, B cells are subjected to programmed genetic recombination processes like VDJ rearrangements and class switch recombination (CSR), which result in deletion of specific sequences of the IGH locus. These cell type-specific DNA "scars" (loss of sequences) in IG genes can be exploited as B cell markers in digital PCR (dPCR) based quantification methods. Here, we describe a novel, specific and sensitive digital PCR-based method to quantify mature and switched B cells in DNA specimens of benign and (copy number unstable) malignant origin. We compared this novel way of B cell quantitation with flow cytometric and immunohistochemical methods. Through cross-validation with flow cytometric sorted B cell subpopulations, we gained quantitative insights into allelic involvement in different recombination processes in the IGH locus. Our newly developed method is accurate and independent of the cellular context, offering new possibilities for quantification, even for (limited) small samples like liquid biopsies.