The clinical utility of molecular diagnostic testing for primary immune deficiency disorders: a case based review

Primary immune deficiency disorders (PIDs) are a group of diseases associated with a genetic predisposition to recurrent infections, malignancy, autoimmunity and allergy. The molecular basis of many of these disorders has been identified in the last two decades. Most are inherited as single gene defects. Identifying the underlying genetic defect plays a critical role in patient management including diagnosis, family studies, prognostic information, prenatal diagnosis and is useful in defining new diseases. In this review we outline the clinical utility of molecular testing for these disorders using clinical cases referred to Auckland Hospital. It is written from the perspective of a laboratory offering a wide range of tests for a small developed country

Solution Structure of Tensin2 SH2 Domain and Its Phosphotyrosine-Independent Interaction with DLC-1

Background: Src homology 2 (SH2) domain is a conserved module involved in various biological processes. Tensin family member was reported to be involved in tumor suppression by interacting with DLC-1 (deleted-in-liver-cancer-1) via its SH2 domain. We explore here the important questions that what the structure of tensin2 SH2 domain is, and how it binds to DLC-1, which might reveal a novel binding mode. Principal Findings: Tensin2 SH2 domain adopts a conserved SH2 fold that mainly consists of five b-strands flanked by two a-helices. Most SH2 domains recognize phosphorylated ligands specifically. However, tensin2 SH2 domain was identified to interact with nonphosphorylated ligand (DLC-1) as well as phosphorylated ligand. Conclusions: We determined the solution structure of tensin2 SH2 domain using NMR spectroscopy, and revealed the interactions between tensin2 SH2 domain and its ligands in a phosphotyrosine-independent manner

Molecular Pathogenesis of EBV Susceptibility in XLP as Revealed by Analysis of Female Carriers with Heterozygous Expression of SAP

X-linked lymphoproliferative disease (XLP) is a primary immunodeficiency caused by mutations in SH2D1A which encodes SAP. SAP functions in signalling pathways elicited by the SLAM family of leukocyte receptors. A defining feature of XLP is exquisite sensitivity to infection with EBV, a B-lymphotropic virus, but not other viruses. Although previous studies have identified defects in lymphocytes from XLP patients, the unique role of SAP in controlling EBV infection remains unresolved. We describe a novel approach to this question using female XLP carriers who, due to random X-inactivation, contain both SAP+ and SAP− cells. This represents the human equivalent of a mixed bone marrow chimera in mice. While memory CD8+ T cells specific for CMV and influenza were distributed across SAP+ and SAP− populations, EBV-specific cells were exclusively SAP+. The preferential recruitment of SAP+ cells by EBV reflected the tropism of EBV for B cells, and the requirement for SAP expression in CD8+ T cells for them to respond to Ag-presentation by B cells, but not other cell types. The inability of SAP− clones to respond to Ag-presenting B cells was overcome by blocking the SLAM receptors NTB-A and 2B4, while ectopic expression of NTB-A on fibroblasts inhibited cytotoxicity of SAP− CD8+ T cells, thereby demonstrating that SLAM receptors acquire inhibitory function in the absence of SAP. The innovative XLP carrier model allowed us to unravel the mechanisms underlying the unique susceptibility of XLP patients to EBV infection in the absence of a relevant animal model. We found that this reflected the nature of the Ag-presenting cell, rather than EBV itself. Our data also identified a pathological signalling pathway that could be targeted to treat patients with severe EBV infection. This system may allow the study of other human diseases where heterozygous gene expression from random X-chromosome inactivation can be exploited

ANALYSIS OF PRODUCT DOPPLER-BROADENED PROFILES GENERATED FROM PHOTOINITIATED BIMOLECULAR REACTIONS

This paper, which is the companion to the experimental paper (M. Brouard, S. P. Duxon, P. A. Enriquez and J. P. Simons, J. Chem. Soc., Faraday Trans., 1993, 89, 1435) in this issue, is divided into two parts. In the first, equations for the laboratory (LAB) velocity distribution of products generated via photoionitiated bimolecular reaction are presented. These equations provide the basis for numerical simulation of these distributions from assumed forms for the centre-of-mass (CM) differential cross-section: the results may be compared directly with those derived experimentally via Fourier-transform Doppler 1 + 1 LIF or REMPI spectroscopy. The latter inversion technique is described in detail in the second part of the paper

Velocity Aligned Photofragment Stereodynamics in the reaction O(1D) + N2O --> NO + NO

The secondary reaction of velocity aligned, superthermal atoms generated via molecular photodissociation can lead to aligned secondary reaction products. Their vector properties and their quantum state distributions can be measured by using Doppler resolved, polarized laser probe techniques. A simple LAB CM transformation can thus be used to determine the vector correlations among k (the bimolecular collision velocity vectors), k (the reaction products' velocity vectors), and j (the reaction products' angular momenta). These are analogous to the (, v, j) correlations in the primary photodissociation. The strategy is demonstrated in a study of the dynamical stereochemistry of the reaction O(1D) + N2O NO + NO. © 1991 American Chemical Society

MEASUREMENTS OF VECTOR CORRELATIONS IN BIOMOLECULAR REACTIONS BY LASER-PUMP AND PROBE TECHNIQUES

Velocity-aligned, superthermal atoms generated via polarised molecular photodissociation have been used to investigate vector correlations of bimolecular reactions. Doppler-resolved, polarised laser-probe techniques can measure correlations between k (the reagents' relative-velocity vectors), k′ (the reaction products' velocity vectors) and J′ (the products' rotational angular momenta using a simple laboratory to centre-of-mass frame transformation. This approach to the study of the dynamical stereo-chemistry of chemical reactions is illustrated by two examples, O(1D)+N2O→NO+NO and O(3P)+CS→CO+S. © 1991