Adenosine deaminase in patients with primary immunodeficiency syndromes: the analysis of serum ADA1 and ADA2 activities.

OBJECTIVES: We aimed to investigate the activity of ADA and its isoenzymes in serum of patients with various primary immunodeficiency (PID) syndromes. DESIGN AND METHODS: Total ADA (tADA) and its isoenzymes were measured in 76 children with PID syndromes and 30 healthy controls using the Ellis method. RESULTS: Our results indicated that tADA and ADA2 levels were higher in patients with Chronic Granulomatous Disease (CGD), Leukocyte Adhesion Deficiency (LAD), hyper IgM (HIM) and Wiskott-Aldrich Syndrome (WAS) than those of corresponding controls (P<0.01). There was a significant elevation of tADA and ADA1 activities in IgA deficiency patients as compared to healthy individuals (P<0.01). CONCLUSIONS: Our results hypothesized that altered ADA activity may be associated with altered immunity. Therefore, serum ADA level could be used as an indicator along with other parameters in follow up of patients with CGD, LAD, IgA deficiency, HIM and WAS.

LAD-III, a leukocyte adhesion deficiency syndrome associated with defective Rap1 activation and impaired stabilization of integrin bonds.

Recently, we reported a rare leukocyte adhesion deficiency (LAD) associated with severe defects in integrin activation by chemokine signals, despite normal ligand binding of leukocyte integrins.(1) We now report that the small GTPase, Rap1, a key regulator of inside-out integrin activation is abnormally regulated in LAD Epstein-Barr virus (EBV) lymphocyte cells. Both constitutive and chemokine-triggered activation of Rap1 were abolished in LAD lymphocytes despite normal chemokine signaling. Nevertheless, Rap1 expression and activation by phorbol esters were intact, ruling out an LAD defect in Rap1 guanosine triphosphate (GTP) loading. The very late antigen 4 (VLA-4) integrin abnormally tethered LAD EBV lymphocytes to its ligand vascular cell adhesion molecule 1 (VCAM-1) under shear flow due to impaired generation of high-avidity contacts despite normal ligand binding and intact avidity to surface-bound anti-VLA-4 monoclonal antibody (mAb). Thus, a defect in constitutive Rap1 activation results in an inability of ligand-occupied integrins to generate high-avidity binding to ligand under shear flow. This is a first report of an inherited Rap1 activation defect associated with a pathologic disorder in leukocyte integrin function, we herein term it "LAD-III."

Defective intracellular activity of GDP-D-mannose-4,6-dehydratase in leukocyte adhesion deficiency type II syndrome.

Leukocyte adhesion deficiency type II (LAD II) is a rare genetic disease characterized by severe immunodeficiency which is related to defective expression in leukocytes of sialyl-Lewis X (SLeX), a fucosylated ligand for endothelial selectins. The molecular basis of LAD II is still unknown, but has been tentatively localized in the de novo pathway of GDP-L-fucose biosynthesis from GDP-D-mannose. Here, we demonstrate that in cell lysates from a LAD II patient, GDP-D-mannose-4,6-dehydratase (GMD), the first of the two enzymes of the pathway has a defective activity compared to control subjects. GMD in cell lysates from both parents showed intermediate activity levels. Cloning of GMD from patient and control lymphocytes ruled out any mutation affecting the amino acid GMD sequence and the purified recombinant proteins from both controls and the patient showed identical specific activities. Since the levels of immunoreactive GMD in cell lysates were comparable in the patient and in controls, the biochemical deficiency of intracellular GMD activity in LAD II seems to be due to mutation(s) affecting some still unidentified GMD-regulating protein.