The interaction between Cdc42 and WASP is required for SDF-1-induced T-lymphocyte chemotaxis

In studies aimed at further characterizing the cellular immunodeficiency of the Wiskott-Aldrich syndrome (WAS), we found that T lymphocytes from WAS patients display abnormal chemotaxis in response to the T-cell chemoattractant stromal cell-derived factor (SDF)-1. The Wiskott- Aldrich syndrome protein (WASP), together with the Rho family GTPase Cdc42, control stimulus-induced actin cytoskeleton rearrangements that are involved in cell motility. Because WASP is an effector of Cdc42, we further studied how Cdc42 and WASP are involved in SDF-1-induced chemotaxis of T lymphocytes. We provide here direct evidence that SDF-1 activates Cdc42. We then specifically investigated the role of the interaction between Cdc42 and WASP in SDF-1-responsive cells. This was achieved by abrogating this interaction with a recombinant polypeptide (TAT-CRIB), comprising the Cdc42/Rac interactive binding (CRIB) domain of WASP and a human immunodeficiency virus-TAT peptide that renders the fusion protein cell-permeant. This TAT-CRIB protein was shown to bind specifically to Cdc42-GTP and to inhibit the chemotactic response of a T-cell line to SDF-1. Altogether, these data demonstrate that Cdc42-WASP interaction is critical for SDF-1-induced chemotaxis of T cells.

V(D)J recombination defects in lymphocytes due to RAG mutations: severe immunodeficiency with a spectrum of clinical presentations

Severe combined immunodeficiency (SCID) comprises a heterogeneous group of primary immunodeficiencies, a proportion of which are due to mutations in either of the 2 recombination activating genes (RAG)-1 and -2, which mediate the process of V(D)J recombination leading to the assembly of antigen receptor genes. It is reported here that the clinical and immunologic phenotypes of patients bearing mutations in RAGs are more diverse than previously thought and that this variability is related, in part, to the specific type of RAG mutation. By analyzing 44 such patients from 41 families, the following conclusions were reached: (1) null mutations on both alleles lead to the T-B-SCID phenotype; (2) patients manifesting classic Omenn syndrome (OS) have missense mutations on at least one allele and maintain partial V(D)J recombination activity, which accounts for the generation of residual, oligoclonal T-lymphocytes; (3) in a third group of patients, findings were only partially compatible with OS, and these patients, who also carried at least one missense mutation, may be considered to have atypical SCID/OS; (4) patients with engraftment of maternal T cells as a complication of a transplacental transfusion represented a fourth group, and these patients, who often presented with a clinical phenotype mimicking OS, may be observed regardless of the type of RAG gene mutation. Analysis of the RAG genes by direct sequencing is an effective way to provide accurate diagnosis of RAG-deficient as opposed to RAG-independent V(D)J recombination defects, a distinction that cannot be made based on clinical and immunologic phenotype alone.

Combined (111)In-pentetreotide scintigraphy and (123)I-mIBG scintigraphy in neuroblastoma provides prognostic information

BACKGROUND

High-affinity somatostatin receptors (SRs) have been characterized in neuroblastomas and may be used as target structures for in vivo detection of SR.

PROCEDURE

Eighty-eight children with histologically proven neuroblastoma were investigated at diagnosis or relapse by (123)I-mIBG and (111)In-pentetreotide scintigraphy. All tumors were investigated for MYCN copy number, chromosome 1p36 status, and 68/88 also for DNA content, followed for a median follow-up of 35 months (range 1-88 months).

RESULTS

SR expression was detected in 56/88 tumors and (123)I-mIBG showed positivity in 83/88. (111)In-pentetreotide was less sensitive in detecting tumor tissue than was (123)I-mIBG (64% vs. 94%, P = 0.005). Survival (SUR) and event-free survival probability (EFS) according to Kaplan-Meier was significantly better for children with positive SR scintigraphy than for the children with a negative SR scan (SUR: 90% vs. 48% at 4 years log rank P < 0.003, EFS: 83% vs. 39% at 4 years, log rank P < 0.0002).

CONCLUSIONS

(123)I-mIBG scintigraphy remains the best scintigraphic method for detecting neuroblastoma tumor tissue, whereas additional SR scintigraphy is able to provide significant prognostic information with a minimum of invasiveness.

Population-based and controlled study to evaluate neuroblastoma screening at one year of age in Germany: interim results

BACKGROUND

The German Neuroblastoma Screening Project is the first controlled and population-based screening study to evaluate the presumed benefit of neuroblastoma mass screening at 1 year of age (10-18 months).

PROCEDURE

Screening takes place in 6 of the 16 German states; children from the remainder serve as controls. The German Childhood Cancer Registry enables a mostly complete follow-up and detection of false-negative patients.

RESULTS

Up to December, 1999, 1,199,165 children were examined for urinary catecholamine metabolites and 124 cases of neuroblastoma were detected preclinically, giving a detection rate of 10.3/100,000. Within this cohort, 33 false-negative cases were found.

CONCLUSIONS

The results of this screening program will be crucial for further implementation of neuroblastoma screening.

The proteasome regulator PA28alpha/beta can enhance antigen presentation without affecting 20S proteasome subunit composition

PA28alpha/beta is a regulatory complex of the 20S proteasome which consists of two IFN-gamma inducible subunits. Both subunits, alpha and beta, contribute equally to the formation of hexa- or heptameric rings which can associate with the 20S proteasome. Previously, we have shown that overexpression of the PA28alpha subunit enhanced the MHC class I-restricted presentation of two viral epitopes and that purified PA28alpha/beta accelerated T cell epitope generation by the 20S proteasome in vitro, indicating a role for PA28alpha/beta in antigen presentation. This conclusion was recently confirmed in PA28beta gene targeted mice which were severely deficient in MHC class I-restricted antigen presentation. These mice displayed a defect in the assembly of immunoproteasomes, suggesting that a lack of the proteasome subunits LMP2, LMP7, and MECL-1 may account for the deficiency in antigen presentation. In this study we investigated whether the effect of PA28alpha/beta on antigen presentation is dependent on a change of proteasome subunit composition. We have analyzed the assembly and subunit composition of proteasomes in fibroblast transfectants overexpressing both, alpha and beta subunits of PA28. In these transfectants we found a marked enhancement in the presentation of the immunodominant H-2Ld-restricted pp89 epitope of murine cytomegalovirus, although the 20S proteasome composition was the same as in recipient cells. We, therefore, conclude that PA28alpha/beta can enhance antigen processing independently of changes in 20S proteasome subunit composition or assembly.

Alterations in leukotriene synthase activity of the human 5-lipoxygenase by site-directed mutagenesis affecting its positional specificity

The positional specificity of arachidonic acid oxygenation is currently the decisive parameter for classification of lipoxygenases. Although the mechanistic basis of lipoxygenase specificity is not completely understood, sequence determinants for the positional specificity have been identified for various isoenzymes. In this study we altered the positional specificity of the human 5-lipoxygenase by multiple site-directed mutagenesis and assayed the leukotriene A(4) synthase activity of the mutant enzyme species with (5S,6E,8Z,11Z,14Z)-5-hydroperoxy-6,8,11,14-eicos atetraenoic acid (5S-HpETE) as substrate. The wild-type 5-lipoxygenase converts 5S-HpETE almost exclusively to leukotriene A(4) as indicated by the dominant formation of leukotriene A(4) hydrolysis products. Since leukotriene synthesis involves a hydrogen abstraction from C(10), it was anticipated that the 15-lipoxygenating quadruple mutant F359W + A424I + N425M + A603I might not exhibit a major leukotriene A(4) synthase activity. Surprisingly, we found that this quadruple mutant exhibited a similar leukotriene synthase activity as the wild-type enzyme in addition to its double oxygenation activity. The leukotriene synthase activity of the 8-lipoxygenating double mutant F359W + A424I was almost twice as high, and similar amounts of leukotriene A(4) hydrolysis products and double oxygenation derivatives were detected with this enzyme species. These data indicate that site-directed mutagenesis of the human 5-lipoxygenase that leads to alterations in the positional specificity favoring arachidonic acid 15-lipoxygenation does not suppress the leukotriene synthase activity of the enzyme. The residual 8-lipoxygease activity of the mutant enzyme and its augmented rate of 5-HpETE conversion may be discussed as major reasons for this unexpected result.

Gamow-teller strengths of the inverse beta transition 176Yb-->176Lu for spectroscopy of proton-proton and other sub-MeV solar neutrinos

Discrete Gamow-Teller (GT) transitions 176Yb-->176Lu at low excitation energies have been measured via the ( 3He,t) reaction at 450 MeV and at 0 degrees. For 176Yb, two low-lying states are observed, setting low thresholds Q(nu) = 301 and 445 keV for neutrino ( nu) capture. Capture rates estimated from the measured GT strengths, the simple two-state excitation structure, and the low Q(nu) in Yb-Lu indicate that Yb-based nu detectors are well suited for a direct measurement of the sub-MeV solar electron-neutrino ( nu(e)) spectrum including pp neutrinos.

Activities of antioxidants are affected by colloidal properties of oil-in-water and water-in-oil emulsions and bulk oils

The activity of alpha-tocopherol, Trolox, propyl gallate, gallic acid, methyl carnosoate, and carnosic acid was studied in two oil-in-water (o/w) emulsions, in two water-in-oil (w/o) emulsions, and in bulk oil with and without added emulsifiers. All antioxidants had either moderate or higher activity in bulk oil than in the emulsions. In most emulsions, the most polar antioxidants, propyl gallate and gallic acid, exhibited either prooxidant activity or no antioxidant activity. Methyl carnosoate was the most active antioxidant in w/o emulsions but was less active than Trolox in o/w emulsions. alpha-Tocopherol was less active in bulk oil than in emulsions, but its activity in bulk oil was markedly enhanced by the addition of o/w emulsifiers. Partitioning of antioxidants, hydrogen bonding, interphase transport, surface accessibility, and interaction of emulsifier with antioxidants are considered to be important parameters that determine antioxidant activity in lipid-containing systems.

Retrovirus-mediated transduction of primary ZAP-70-deficient human T cells results in the selective growth advantage of gene-corrected cells: implications for gene therapy

Humans lacking the ZAP-70 protein tyrosine kinase present with an absence of CD8+ T cells and defective CD4+ T cells in the periphery. This severe combined immunodeficiency is fatal unless treated by allogeneic bone marrow transplantation. However, in the absence of suitable marrow donors, the development of alternative forms of therapy is desirable. Because lymphocytes are long-lived, it is possible that introduction of the wild-type ZAP-70 gene into CD4+ ZAP-70-deficient T cells will restore their immune function in vivo. Initial investigations evaluating the feasibility of gene therapy for ZAP-70 deficiency were performed using HTL V-I-transformed lymphocytes. Although transformation was useful in circumventing problems associated with the maintenance of ZAP-70-deficient T cells and low gene transfer levels, the presence of HTL V-I precluded any biological studies. Here, we investigated a retrovirus-mediated approach for the correction of primary T cells derived from two ZAP-70-deficient patients. Upon introduction of the wild-type ZAP-70 gene, TCR-induced MAPK activation, IL-2 secretion and proliferation were restored to approximately normal levels. Importantly, this gain-of-function was associated with a selective growth advantage of gene-corrected cells, thereby indicating the feasibility of a gene therapy-based strategy.

Overexpression of the proteasome subunits LMP2, LMP7, and MECL-1, but not PA28 alpha/beta, enhances the presentation of an immunodominant lymphocytic choriomeningitis virus T cell epitope

The proteasome is a large protease complex that generates most of the peptide ligands of MHC class I molecules either in their final form or in the form of N-terminally extended precursors. Upon the stimulation of cells with IFN-gamma, three constitutively expressed subunits of the 20S proteasome are replaced by the inducible subunits LMP2 (low-molecular mass polypeptide 2), LMP7, and MECL-1 (multicatalytic endopeptidase complex-like-1) to form so-called immunoproteasomes. We show in this study that overexpression of these three subunits in triple transfectants led to a marked enhancement in the H-2Ld-restricted presentation of the immunodominant nonameric epitope NP118, which is derived from the nucleoprotein (NP) of lymphocytic choriomeningitis virus. Overexpression of the alpha and beta subunits of the IFN-gamma-inducible proteasome regulator PA28, in contrast, did not have a comparable effect. In vitro, immunoproteasomes as compared with constitutive proteasomes generated higher amounts of 11- and 12-mer fragments containing the NP118 epitope. These are likely to be cytosolic precursors of NP118, as a proline anchor residue in the second position of NP118 may interfere with TAP-mediated transport of the nonameric epitope itself. In conclusion, we provide evidence that up-regulation of the three inducible subunits, LMP2, LMP7, and MECL-1, can result in a marked improvement of Ag presentation and that, depending on the epitope, PA28 and immunoproteasomes may differentially affect Ag processing.

The polarization defect of Wiskott-Aldrich syndrome macrophages is linked to dislocalization of the Arp2/3 complex

Wiskott-Aldrich syndrome (WAS) is an X-linked recessive disorder originally characterized by the clinical triad eczema, thrombocytopenia, and severe immunodeficieny, with recurrent bacterial and viral infections, indicating a profound immune cell defect. Such altered immune cells include monocytes, macrophages, and dendritic cells, which were reported to display disturbed cell polarization or chemotaxis. WAS is caused by mutations in the WAS protein (WASp), which is thought to organize the actin cytoskeleton through the Arp2/3 complex. Here we show that the Arp2/3 complex is an integral part of podosomes, actin-rich adhesion structures of macrophages, and that WAS macrophages fail to organize the Arp2/3 complex into podosomes. We also demonstrate that microinjection of a C-terminal acidic stretch of WASp into normal macrophages displaces Arp2/3 from podosomes and, in combination with chemoattractant stimulation of cells, induces a phenotype resembling the polarization-defective phenotype of stimulated WAS macrophages. These findings point to an important role of the Arp2/3 complex in polarization and migration of immune cells.

PCR analysis of IgH-gene rearrangements in small lymphoid infiltrates microdissected from sections of paraffin-embedded bone marrow biopsy specimens

The differentiation of benign lymphoid infiltrates from nodular infiltrates of B-cell lymphoma is difficult in bone marrow (BM) biopsy specimens taken from patients with non-Hodgkin's lymphoma (NHL). We investigated whether the determination of clonality by polymerase chain reaction (PCR) analysis of the immunoglobulin heavy chain (IgH) genes could be of help for the distinction of benign and malignant lymphoid infiltrates. BM biopsy specimens of 28 patients were studied, comparing PCR of entire bone marrow sections with microdissected nodular lymphoid infiltrates. Patients were divided into 4 groups according to morphologic criteria: group 1 (n = 12), positive for B-NHL infiltration; group 2 (n = 5), suspicious for infiltration by known B-NHL; group 3 (n = 5), morphologically benign infiltrates in patients with B-NHL; group 4 (n = 6), benign lymphoid infiltrates in patients without history of B-NHL. PCR products were analyzed using polyacrylamide gels and a fragment length analysis system (Genescan). PCR of whole sections showed clonal amplification products in all cases of group 1 and 1 case of group 2. PCR analysis from microdissected nodular infiltrates showed the presence of a clonal B-cell population in 5 additional cases of groups 2 and 4. In 3 of these cases, clonal rearrangements of corresponding size were obtained from the primary lymphoma biopsy specimens. None of the cases of group 3 showed evidence of a clonal population with either technique. The results indicate that microdissection of small nodular lymphoid infiltrates from paraffin-BM sections increases the sensitivity of IgH gene rearrangement analysis. To avoid detection of biologically irrelevant clonal populations, comparison of PCR products obtained from the BM and the primary lymphoma biopsy is advisable.

Alternative antigen receptor (TCR) signaling in T cells derived from ZAP-70-deficient patients expressing high levels of Syk

ZAP-70-deficient patients present with nonfunctional CD4+ T cells in the periphery. We find that a subset of primary ZAP-70-deficient T cells, expressing high levels of the related protein-tyrosine kinase Syk, can proliferate in vitro. These cells (denoted herein as Syk(hi)/ZAP-70(-) T cells) provide a unique model in which the contribution of Syk to TCR-mediated responses can be explored in a nontransformed background. Importantly, CD3-induced responses, such as tyrosine phosphorylation of cellular substrates (LAT, SLP76, and PLC-gamma1), as well as calcium mobilization, which are defective in T cells expressing neither ZAP-70 nor Syk, are observed in Syk(hi)/ZAP-70(-) T cells. However, Syk(hi)/ZAP-70(-) T cells differ from control T cells with respect to the T cell antigen receptor (TCR)-mediated activation of the MAPK cascades: extracellular signal-regulated kinase activity and recruitment of the JNK and p38 stress-related MAPK pathways are diminished. This distinct phenotype of Syk(hi)/ZAP-70(-) T cells is associated with a profound decrease in CD3-mediated interleukin 2 secretion and proliferation relative to control T cells. Thus, ZAP-70 and Syk appear to play distinct roles in transducing a TCR-mediated signal.