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Biomedical subjects

J Andersson

Publications and source records attributed to J Andersson.

At least 19 recordsLinked to original sources
PubMed1999

Perforin is not co-expressed with granzyme A within cytotoxic granules in CD8 T lymphocytes present in lymphoid tissue during chronic HIV infection.

BACKGROUND: Residual HIV-1-infected cells are poorly eliminated from lymphoid tissue (LT) reservoirs by effector cytotoxic T lymphocytes (eCTL) despite antiretroviral therapy. Perforin and granzyme A (grA) constitute major effector molecules within eCTL granules that induce apoptosis and lysis of virally infected cells. OBJECTIVE: Expression of perforin and grA was studied at the single cell level in LT and blood from 16 patients infected with HIV-1 (stage A1-C) who were not taking antiretroviral therapy. METHOD: Immunohistochemical analysis by in situ imaging of cells from blood and LT. RESULTS: Quantitative in situ imaging showed that perforin-expressing CD8 T cells comprised 0.3-1.5% of total cells within the LT from recent HIV-1 seroconverters, while grA was found in 2.1-7.2% of total cells. However, despite high-level grA upregulation (1.5-4.5% of total cells) compared with that in non-infected individuals (0.4-0.9%), perforin expression remained low (< 0.1% of total cells) (P < 0.02) in LT from patients with chronic HIV-1 infection (stage A2-C). This contrasted with findings in peripheral blood mononuclear cells (PBMC) from the same HIV-1 infected cohort where perforin was detected in 13-31% of all PBMC, which was 10- to 100-fold higher than in lymphoid tissue (P < 0.001); grA was found in 14-32% of total PBMC. Two-colour staining showed that granular expression of perforin and grA was restricted to CD8 T cells in over 90% of total cells in both LT and blood. CONCLUSIONS: These findings indicate that cytotoxic perforin expression is impaired at local sites of HIV replication within lymphoid tissue. Since perforin is required together with grA for granule-mediated cytolysis, the low perforin expression in the LT may limit the ability of eCTL to eliminate HIV-1 infected cells in lymphoid tissue.

CD4 Lymphocyte Count↗
PubMed1999

Functional gene transfer of HIV DNA by an HIV receptor-independent mechanism.

HIV-1 enters target cells mainly via binding to CD4 and its coreceptors. The presence of HIV-1 in CD4- cells suggests, however, that there exist other mechanisms for viral entry. Here it is reported that HIV-1 DNA may be transferred from one cell to another by uptake of apoptotic bodies in a CD4-independent way. This was investigated by coculturing CD4-, chemokine receptor CCR5- and CXCR4- human fetal fibroblasts with apoptotic HIV-1-infected HuT78 cells or apoptotic PBMC isolated from HIV-1-infected patients. After 2 wk of coculture, fibroblasts contained HIV-1 DNA and expressed HIV-1 proteins p24 and gp120. Transfer of HIV-1 DNA was verified by coculturing fibroblasts with apoptotic bodies derived from cells infected with a defective HIV-1 virus. These cells contain one integrated copy of a reverse transcriptase (RT)-negative HIV-1 strain (8E5/LAV RT- cells) and consequently cannot produce free virus. Intracellular HIV-1 gag DNA was detected in both fibroblasts and dendritic cells after coculture with apoptotic 8E5/LAV RT- cells. Transfer of viral DNA after uptake of apoptotic bodies may explain HIV-1 infection of CD4- cells in vivo and furthermore may be relevant for Ag presentation.

Apoptosis↗
PubMed1999

HMG-1 as a late mediator of endotoxin lethality in mice.

Endotoxin, a constituent of Gram-negative bacteria, stimulates macrophages to release large quantities of tumor necrosis factor (TNF) and interleukin-1 (IL-1), which can precipitate tissue injury and lethal shock (endotoxemia). Antagonists of TNF and IL-1 have shown limited efficacy in clinical trials, possibly because these cytokines are early mediators in pathogenesis. Here a potential late mediator of lethality is identified and characterized in a mouse model. High mobility group-1 (HMG-1) protein was found to be released by cultured macrophages more than 8 hours after stimulation with endotoxin, TNF, or IL-1. Mice showed increased serum levels of HMG-1 from 8 to 32 hours after endotoxin exposure. Delayed administration of antibodies to HMG-1 attenuated endotoxin lethality in mice, and administration of HMG-1 itself was lethal. Septic patients who succumbed to infection had increased serum HMG-1 levels, suggesting that this protein warrants investigation as a therapeutic target.

Animals↗
PubMed1999

A glycyl radical site in the crystal structure of a class III ribonucleotide reductase.

Ribonucleotide reductases catalyze the reduction of ribonucleotides to deoxyribonucleotides. Three classes have been identified, all using free-radical chemistry but based on different cofactors. Classes I and II have been shown to be evolutionarily related, whereas the origin of anaerobic class III has remained elusive. The structure of a class III enzyme suggests a common origin for the three classes but shows differences in the active site that can be understood on the basis of the radical-initiation system and source of reductive electrons, as well as a unique protein glycyl radical site. A possible evolutionary relationship between early deoxyribonucleotide metabolism and primary anaerobic metabolism is suggested.

Acetyltransferases↗
PubMed1999

Effect of deregulated IL-7 transgene expression on B lymphocyte development in mice expressing mutated pre-B cell receptors.

Deregulated overexpression of IL-7 under the control of the promoter of the Ealpha gene of MHC class II in IL-7-transgenic mice changes B cell development in wild-type mice and in mutants which limit B cell development at various cellular stages. While the introduction of deregulated IL-7 production does not change the size of the pro-B and pre-B I compartments in the bone marrow of wild-type and lambda5-/- mice, it increases these compartments 2.5- to fivefold in mice which cannot make immature and mature B cells, i. e. in RAG-2-/-, tmmuH-/-, and RAG-2-/- mice expressing a transgenic muH chain. Excessive IL-7 production also increases four- to fivefold the pre-B II compartment in all those mouse strains where it can be formed (i. e. in wild-type, lambda5-/- and muH chain-transgenic RAG-2-/- mice), while no pre-B- II-like cells appear in excessively IL-7-stimulated bone marrow of mice devoid of pre-B II cells (i. e. in tmmuH-/- and RAG-2-/- mice). In the spleen of all IL-7-transgenic mice significant numbers of both pro-B and pre-B I cells are detectable and increased numbers of pre-B II and immature B cells appear in the spleen of mouse strains which are capable of making them. The capacity of the spleen to accommodate expanded numbers of these B-lineage cells as well as mature B cells is much larger than that of the bone marrow of the IL-7-transgenic mice probably because the bone limits cellular expansion and provokes spillover into the peripheral lymphoid organs.

Animals↗
PubMed1999

Regulation of CCR5 and CXCR4 expression by type 1 and type 2 cytokines: CCR5 expression is downregulated by IL-10 in CD4-positive lymphocytes.

HIV-1 transmission and disease progression is, in general, characterized by initial predominance of macrophage tropic, non-syncytium-inducing strains followed by a switch to T-cell tropic, syncytium-inducing strains. Using sensitive, quantitative kinetic RT-PCR, we examined cytokine regulation of tropism-specific HIV-1 coreceptor expression in PBMCs from HIV-1-seronegative individuals. Proinflammatory (TNF-alpha and IL-12) and type 1 cytokines (IFN-gamma and IL-2) significantly upregulated CCR5 (wt allele) mRNA expression in CCR5 homozygous wild-type (wt/wt) and heterozygous individuals (wt/del) (P < 0.02). CCR5 (wt) mRNA expression in unstimulated PBMCs was significantly increased in wt/wt individuals compared to that of wt/del individuals (P < 0.01). In wt/del individuals, del CCR5 mRNA was expressed at 10-fold greater levels than wt CCR5 mRNA in unstimulated PBMCs from the same individual. Flow cytometry confirmed that upregulated CCR5 mRNA following type 1 cytokine stimulation leads to increased cell surface expression of CCR5 protein. The type 2 cytokine IL-10 downregulated both CCR5 mRNA and protein expression in wt/wt and wt/del individuals. Proinflammatory, type 1, and type 2 cytokines significantly increased CXCR4 mRNA expression in wt/wt, wt/del, and del/del CCR5 genotypes (P < 0.02). These results suggest that changes in the cytokine milieu influence chemokine receptor expression and may explain emergence of tropism-specific strains facilitating HIV transmission and disease progression.

Base Sequence↗
PubMed1999

The roles of preB and B cell receptors in the stepwise allelic exclusion of mouse IgH and L chain gene loci.

Membrane-bound preBCR of wild-type mice, and probably also preBCR-like V(preB) muH chain complexes in lambda5-deficient mice, signal allelic exclusion so that < 0.1% of all preB-II cells and all subsequent B lineage cells express two muH chains on their surface. On the other hand a large number of muH chains which are originally generated at the transition of preB-I to preB-II cells cannot pair with surrogate L chains, cannot form a preBCR on the surface and, hence, allow two H chain alleles to be productively rearranged in one B-lineage cell. By contrast membrane-bound BCR on immature B cells does not signal allelic or isotypic exclusion Of Ig kappaL and lambdaL chain gene loci. This allows the rearrangement machinery to remain active, and secondary L chain rearrangements on one kappaL chain allele are frequently observed. Rapid selection of fitting H/L chain pairs, forming BCR on the surface, allows B-lineage cells to enter the mature B cell pool where the rearrangement machinery is shut off, securing allelic exclusion of L chain loci in most B cells.

Alleles↗
PubMed1999

Mutations affecting either generation or survival of cells influence the pool size of mature B cells.

The mature B cell compartment of MHC class II-deficient B6 I-Aalpha(-/-) and the btk-defective CBA/N mouse strain is 4- to 5-fold smaller than in wild-type B6 mice. The defect in B6 I-Aalpha(-/-) mice is intrinsic to B cells and due to a 4- to 5-fold reduced lifespan, which however can be normalized by an I-Ealpha(d) transgene, but only when expressed early during B cell development. The reduced number of mature B cells in the btk-defective CBA/N mouse is due to a 4- to 5-fold lower number of immature splenic B cells entering the mature compartment. The combined defects of reduced lifespan and impaired generation in double mutant mice result in a severe deficiency in the mature B cell pool.

Animals↗
PubMed1999

Four of five RAG-expressing JCkappa-/- small pre-BII cells have no L chain gene rearrangements: detection by high-efficiency single cell PCR.

Single cell PCR assays have been further developed that detect over 80% of all VkappaJkappa, VkappaRS, and VlambdaJlambda rearrangements at efficiencies between 70% and 90%. These IgL chain gene rearrangement assays were used with small pre-BII cells that develop in comparably high numbers in the bone marrow of wild-type, Ckappa-deficient, and JCkappa-deficient homozygous and heterozygous mice. In all of these mice, only 15%-25% of all small pre-BII cells carry VlambdaJlambda rearrangements. These results confirm that lambdaL chain gene rearrangements occur independently of kappaL chain gene rearrangement and expression. They also show that a large part of the small pre-BII cells that express the rearrangement machinery can develop without IgL chain gene rearrangements.

Animals↗
PubMed1999

Frequencies of multiple IgL chain gene rearrangements in single normal or kappaL chain-deficient B lineage cells.

PCR analyses of the kappaL chain locus in single B-lineage cells of wild-type, Ckappa-, or JCkappa-deficient homozygous or heterozygous mice often detect multiple in- and out-of-frame rearrangements at the kappaL and lambdaL loci. They are most frequent in small pre-BII cells and equally so in wild-type and kappaL chain-deficient cells. Hence, kappaL chain production appears not to inhibit secondary rearrangements. Around 20% of all small preBII cells express IgL chains in their cytoplasm. Cells with a first productive rearrangement on one allele are favored to enter the immature B cell compartment. Thus, allelic exclusion might be secured by control of accessibility of IgL chain loci for rearrangement and by rapid selection of cells with a fitting over those with a nonfitting IgL chain.

Alleles↗
PubMed1999

The distinct role of CD4+ and CD8+ T-cells during the anti-tumour effects of targeted superantigens.

To target T-cells to the tumour area we created a recombinant protein of the bacterial superantigen (SAg) Staphylococcal enterotoxin A (SEA) and the Fab-fragment of a tumour-reactive antibody. This antibody-targeted SAg immunotherapy therapy has been shown to be highly efficient, eliminating > 95% of the pulmonary metastasis in mice carrying established melanoma micrometastases. Earlier studies demonstrated that elimination of the C215-expressing B16-melanoma lung metastasis was dependent on interferon (IFN)-gamma release and expression of perforin. In the present study, therapeutic effector functions were analysed both locally at the tumour site and systemically in the spleen. In order to elucidate the role of each T-cell subset during Fab-SEA therapy, CD4 knock-out (KO) and CD8 KO mice were used. Tumour size reduction was statistically significant in Fab-SEA-based tumour therapy in both types of T-cell-deficient mice compared to wild-type mice. CD4 KO mice displayed a drastic reduction in the number of tumour-infiltrating macrophages and CD8+ T-cells. Therapy-induced accumulation of perforin-containing cells at the tumour site was significantly impaired in CD8 KO mice, and marginally in CD4 KO mice. Moreover, CD4 KO mice failed to produce substantial amounts of the tumour suppressive cytokine IFN-gamma. This is in sharp contrast to normal mice where a massive local release was recorded. CD8 KO mice displayed a spontaneous production of interleukin (IL)-4 and IL-10 locally in the tumour. Neither normal nor CD4 KO mice produced detectable levels of these Th-2-associated cytokines. The high level of IL-10 was demonstrated to inhibit Fab-SEA tumour therapy, since the therapeutic efficacy was significantly higher in IL-10 KO mice. These results illustrate the importance of a finely tuned cellular collaboration to regulate the various phases of an efficient anti-tumour immune response.

Animals↗
PubMed1999

A speechreading expert: the case of MM.

The present case study of MM, who acquired both sign language and spoken language in her early preschool years-and then reached the normal milestones of development in each language--revealed that her speechreading expertise is associated with cognitive functions such as high working memory capacity and phonological skills. Her cognitive profile is in accord with previous case studies of extremely good speechreading skill. MM's enhanced right prefrontal/frontal cerebral blood flow activation during speechreading seems to be indicative of efficient visual scanning, but it is also possibly due to her strategy for phonological decoding of visual speech.

Adult↗
PubMed1999

Anti-inflammatory effects of a new tumour necrosis factor-alpha (TNF-alpha) inhibitor (CNI-1493) in collagen-induced arthritis (CIA) in rats.

A recently developed compound, a multivalent guanylhydrazone (CNI-1493) that inhibits TNF-alpha production by suppressing TNF-alpha translational efficiency, was administered in an experimental model of collagen type II-induced arthritis in DA rats. CNI-1493 was injected daily intraperitoneally either before the onset of arthritis or after the establishment of clinical disease. Prophylactic treatment with CNI-1493 significantly prevented or delayed the onset and suppressed the severity of arthritis in a dose-dependent manner. Therapeutic intervention with CNI-1493 in established joint disease also resulted in a significant reduction of clinical signs of arthritis in treated animals. No severe side-effects were noted when animals were treated with daily CNI-1493 doses up to 5 mg/kg. An immunohistochemical study was performed which demonstrated that CNI-1493 led to a reduced expression of TNF-alpha at the site of disease activity. Thus, CNI-1493 with documented inhibitory effects on TNF-alpha synthesis, has proven successful in ameliorating the course of arthritis in CIA. We believe that the use of a compound such as CNI-1493 with a defined mode of action provides a useful tool for dissecting and understanding important pathogenic mechanisms operating in the development of chronic arthritis.

Animals↗