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Severe combined immunodeficiencies (SCIDs) correspond to the most severe form of primary immunodeficiency. The extreme severity of the clinical presentation in SCID has legitimately led physicians to consider these conditions as medical emergencies. Hundreds of patients worldwide have undergone allogeneic haematopoietic stem cell transplantation (HCST) in the last 40 years. The complete absence of the T cell compartment in SCID prompted the development (starting in the early 1980s) of haploidentical, parental HSCT for the many patients who do not have a human leucocyte antigen (HLA)-identical sibling. Despite the undeniable progress made in this field over recent years, the long-lasting immunodeficiency that follows partially HLA-incompatible transplantation is still responsible for a mortality rate of 30% at one year post-transplantation. New approaches for reconstituting T cell compartments more rapidly are under intense preclinical development and are discussed herein., (© 2012 Blackwell Publishing Ltd.)

Age-matched reference values are generally presented with 5th and 95th percentiles as 'normal' reference range. However, they are mostly determined in relatively small groups, which renders this presentation inaccurate. We determined reference values for B-lymphocyte subpopulations in healthy children with the statistical method of tolerance intervals that deals far better with the relatively small numbers tested, and compared these to the cut-off values used in the currently used EUROclass classification for common variable immunodeficiency disorders (CVID) in children. CVID is a heterogeneous group of primary immunodeficiency diseases characterized by low serum immunoglobulin levels and inadequate response to vaccination. Disease-modifying heterozygous amino acid substitutions in TACI are found in around ±10% of CVID patients. Interestingly, we found that age is the primary determinant of TACI-expression on B-lymphocytes, independent of switched memory B-lymphocyte numbers. Immunophenotyping of B-lymphocyte subpopulations is increasingly used to classify patients with CVID into subgroups with different clinical prognosis according to the composition of their B-lymphocyte compartment. These classifications were mainly developed with data obtained in adults. Because of the maturing paediatric immune system, they may not be equally applicable in children: our and other age-matched reference values show great changes in the composition of the B-lymphocyte compartment during development. Although the greatest changes in B-lymphocyte subpopulations occur below the age of 2 years, when the diagnosis of CVID cannot yet be made, it is likely that a classification developed in adults cannot be used to classify the prognosis of children., (© 2011 The Authors. Scandinavian Journal of Immunology © 2011 Blackwell Publishing Ltd.)