Quantification of κ-deleting recombination excision circles in Guthrie cards for the identification of early B-cell maturation defects.
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ABSTRACT: The vast majority of patients suffering from a primary immunodeficiency (PID) have defects in their T- and/or B-cell compartments. Despite advances in molecular diagnostics, in many patients no underlying genetic defect has been identified. B- and T-lymphocytes are unique in their ability to create a receptor by genomic rearrangement of their antigen receptor genes via V(D)J recombination. During this process, stable circular excision products are formed that do not replicate when the cell proliferates. Excision circles can be reliably quantified using real-time quantitative (RQ-)PCR techniques. Frequently occurring δREC-ψJα T-cell receptor excision circles (TRECs) have been used to assess thymic output and intronRSS-Kde recombination excision circles (KREC) to quantify B-cell replication history. In this perspective, we describe how TRECs and KRECs are formed during precursor - T- and B-cell differentiation, respectively. Furthermore, we discuss new insights obtained with TRECs and KRECs and specifically how these excision circles can be applied to support therapy monitoring, patient classification and newborn screening of PID.Frontiers in Immunology 05/2011; 2:12. DOI:10.3389/fimmu.2011.00012
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ABSTRACT: Severe combined immunodeficiency (SCID) and X-linked agammaglobulinemia (XLA) are inborn errors of immune function that require prompt diagnosis and treatment to prevent life-threatening infections. The lack of functional T or B lymphocytes in these diseases serves as a diagnostic criterion and can be applied to neonatal screening. A robust triplex PCR method for quantitation of T-cell receptor excision circles (TRECs) and κ-deleting recombination excision circles (KRECs), using a single Guthrie card punch, was developed and validated in a cohort of 2560 anonymized newborn screening cards and in 49 original stored Guthrie cards from patients diagnosed with SCID, XLA, ataxia-telangiectasia, Nijmegen-breakage-syndrome, common variable immunodeficiency, immunoglobulin A deficiency, or X-linked hyper-IgM syndrome. Simultaneous measurement of TREC and KREC copy numbers in Guthrie card samples readily identified patients with SCID, XLA, ataxia-telangiectasia and Nijmegen-breakage-syndrome and thus facilitates effective newborn screening for severe immunodeficiency syndromes characterized by the absence of T or B cells.Blood 11/2011; 119(11):2552-5. DOI:10.1182/blood-2011-08-371021 · 10.43 Impact Factor
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ABSTRACT: Population-based newborn screening for severe combined immunodeficiency (SCID) and related disorders has been instituted in five states, with several more planning to add this testing to their newborn screening panels. This review summarizes the rationale, development and implementation of SCID screening programs to date and highlights current and future challenges. Early results of T-cell receptor excision circle (TREC) testing newborns in pilot states indicate that this addition to the newborn screening panel can be successfully integrated into state public health programs. The TREC test has clinical validity and TRECs, as predicted, are an excellent biomarker of poor T lymphocyte production in the thymus or increased lymphocyte loss resulting in T-cell lymphopenia. A variety of cases with typical SCID genotypes and other conditions have been detected in a timely manner and referred for appropriate early treatment. Early detection of primary immunodeficiency is recognized as important for avoiding infectious complications that compromise outcomes. Routine screening of all newborns with the TREC test, implemented as part of an integrated public health program, can achieve presymptomatic diagnosis of SCID and other disorders with T-cell lymphopenia, allowing prompt and effective treatment and leading to a better understanding of the spectrum of these disorders and how to manage them.Current opinion in pediatrics 12/2011; 23(6):667-73. DOI:10.1097/MOP.0b013e32834cb9b0 · 2.74 Impact Factor