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Biomedical subjects

A Svejgaard

Publications and source records attributed to A Svejgaard.

At least 91 records · Page 5Linked to original sources
PubMed1997

Constitutive activation of a slowly migrating isoform of Stat3 in mycosis fungoides: tyrphostin AG490 inhibits Stat3 activation and growth of mycosis fungoides tumor cell lines.

Mycosis fungoides (MF) is a low-grade cutaneous T cell lymphoma of unknown etiology. In this report, the Jak/Stat (Janus kinase/signal transducer and activator of transcription) signaling pathway was investigated in tumor cell lines established from skin biopsy specimens from a patient with MF. Jaks link cytokine receptors to Stats, and abnormal Jak/Stat signaling has been observed in some hemopoietic cancers. In MF tumor cells, a slowly migrating isoform of Stat3, Stat3(sm), was found to be constitutively activated, i.e., (i) Stat3(sm) was constitutively phosphorylated on tyrosine residues, and tyrosine phosphorylation was not enhanced by growth factor stimulation; (ii) band shift assays and immunoprecipitations of DNA/Stat complexes showed constitutive DNA-binding properties of Stat3(sm); and (iii) Stat3(sm) was constitutively associated with Jak3. The abnormal activation of Stat3(sm) was highly specific. Thus, neither the fast migrating isoform of Stat3 (Stat3(fm)) nor other Stats (Stat1, Stat2, and Stat4 through Stat6) were constitutively activated. The Jak kinase inhibitor, tyrphostin AG490, blocked the constitutive activation of Stat3(sm) and inhibited spontaneous as well as interleukin 2-induced growth of MF tumor cells. In conclusion, we have provided evidence for an abnormal Jak/Stat signaling and growth regulation in tumor cells obtained from affected skin of an MF patient.

Cell Division↗
PubMed1997

Susceptibility to HIV infection and progression of AIDS in relation to variant alleles of mannose-binding lectin.

BACKGROUND: Low serum concentrations of mannose-binding lectin (MBL) are associated with increased susceptibility to recurrent infection. Three variant alleles in the MBL gene (B, C, and D), cause low serum concentrations of the protein. We investigated whether variant alleles of MBL affect susceptibility to infection with HIV and progression of AIDS. METHODS: Between 1983 and 1986, all men who attended two clinics in Copenhagen for HIV screening were invited to take part in our study. We investigated the prevalence of variant alleles of MBL (detected by PCR) and assessed the prognostic value of these alleles and the corresponding serum MBL concentrations (measured by ELISA) in 96 homosexual men with HIV infection and in two control groups (123 healthy adults and 36 HIV-negative homosexual men at high risk of HIV infection because of their sexual behaviour). Follow-up was for up to 10 years. FINDINGS: Eight (8%) of the HIV-infected men were homozygous for the variant MBL alleles compared with one (0.8%) of the healthy controls (p = 0.005) and none of the high-risk homosexual controls (p = 0.05). We found no significant association between MBL genotype and time from first positive HIV test to progression of AIDS (p = 0.8). However, in the 61 HIV-infected men who developed AIDS, the median survival time was significantly shorter after the AIDS diagnosis for men who were carriers of the variant alleles (both homozygous and heterozygous) than for men homozygous for the normal MBL allele (11 [IQR 4-21] vs 18 months [9-44], p = 0.007). Among men who developed AIDS, there was a significant difference in survival time between those with serum MBL concentrations below the lower quartile, those within the IQR, and those above the upper quartile (p = 0.02). Multivariate analysis showed that men who developed AIDS and had low serum MBL concentrations had an increased rate of rapid death, independently of CD4 T-cell counts at AIDS diagnosis. INTERPRETATION: Our findings suggest that homozygous carriers of variant MBL alleles are at increased risk of HIV infection, either directly or indirectly because of increased susceptibility to coinfections. These alleles are also associated with a significantly shorter survival time after a diagnosis of AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1997

HLA typing in acute optic neuritis. Relation to multiple sclerosis and magnetic resonance imaging findings.

OBJECTIVE: To study the association of brain magnetic resonance imaging (MRI) findings and HLA findings to clarify the relationship between monosymptomatic optic neuritis (ON) and ON as part of clinically definite multiple sclerosis (CDMS). DESIGN: Population-based cohort of patients with ON referred prospectively during 6 years by neurologists and ophthalmologists within 4 weeks of onset of ON. SETTING: Referral center in the general community of greater Copenhagen (Denmark) (population, 1.5 million). PATIENTS: A consecutive sample of 199 patients aged 12 to 59 years with ON (133 with idiopathic ON, 66 with ON + CDMS), ethnically matched with 192 healthy volunteers. MAIN OUTCOME MEASURES: Relation between the HLA-DR15, -DR17, -DQA-1B, and -DQB-1B polymorphisms as defined by restriction fragment length polymorphism analysis, and presence of plaques on T2-weighted brain MRI. RESULTS: The frequency of HLA-DR15 was significantly increased in patients with ON + CDMS (52%) and ON (47%) compared with control subjects (31%). The frequency of HLA-DR17 was almost equal in the ON + CDMS (18%), ON (23%), and control (23%) groups. The frequencies of HLA-DQA-1B (55% in ON + CDMS, 58% in ON) and HLA-DQB-1B (49% in ON + CDMS, 59% in ON) were significantly increased compared with control subjects (41%, HLA-DQA-1B; 37%, HLA-DQB-1B). Brain MRI was abnormal in 48 of 56 examined patients with ON + CDMS and in 64 of 120 examined patients with ON (P < .001). In contrast, the frequencies of HLA alleles did not differ between patients with and without demyelinating lesions. However, patients with ON and normal MRI findings did not show association with HLA-DR15. CONCLUSIONS: The frequencies of alleles were similar in patients with ON and ON + CDMS, confirming that they are not 2 immunogenetically distinct disease entities. The heterogeneity within the group of patients with ON suggests that the HLA-DR15 molecule is involved in susceptibility to initial demyelinating lesion formation.

Acute Disease↗
PubMed1997

Protein phosphatase 2A plays a critical role in interleukin-2-induced beta 2-integrin dependent homotypic adhesion in human CD4+ T cell lines.

Besides its function as a growth factor for T lymphocytes, interleukin 2 (IL-2) induces beta 2-integrin mediated adhesion, migration, and extravasation of T lymphocytes. It is, however, largely unknown how IL-2 receptors (IL-2R) are coupled to the beta 2-integrin adhesion pathway. Because IL-2 modulates enzymatic activity and/or subcellular distribution of serine/threonine phosphatases 1 and 2A (PP1/PP2A) in T cells, we examined the role of these phosphatases in IL-2 induced homotypic adhesion in antigen specific human CD4+ T cell lines. We show that calyculin A, a potent inhibitor of PP1 and PP2A, blocks PP1/PP2A activity and IL-2 induced adhesion, whereas cyclosporin A, an inhibitor of protein serine/threonine phosphatase 2B (PP2B), does not, suggesting that PP1 and/or PP2A are involved in IL-2 induced adhesion. Endothall, which preferentially inhibits PP2A, strongly inhibited cytokine induced adhesion, whereas the structurally related compound 1,4-dimethylendothall had no effect on either phosphatase activity or the adhesion response. Okadaic acid, which preferentially inhibits PP2A, almost completely blocked IL-2-induced adhesion, whereas tautomycin, a potent inhibitor of PP1, had no inhibitory effect on cytokine induced adhesion at concentrations which strongly inhibited phosphatase activity. In conclusion, these data provide evidence that PP2A plays a critical role in IL-2-induced beta 2-integrin-dependent adhesion of human T cell lines.

CD18 Antigens↗
PubMed1997

The normally expressed kappa immunoglobulin light chain gene repertoire and somatic mutations studied by single-sided specific polymerase chain reaction (PCR); frequent occurrence of features often assigned to autoimmunity.

The expressed human kappa light chain gene repertoire utilized by healthy individuals was studied by two different single-sided specific PCR techniques to avoid bias for certain V genes. A total of 103 rearranged kappa sequences from peripheral blood mononuclear cells from healthy individuals were cloned from cDNA and assigned to the Vkappa and Jkappa germ-line genes with the closest overall homology. The use of cDNA rather than genomic DNA focused the analysis on activated B cells rich in mRNA. Accordingly, the sequences represented the applied repertoire and almost all were somatically mutated. V genes from the Jkappa-proximal duplication unit of the kappa locus were almost exclusively used. A total of 65% of the sequences could be assigned to four or five genes: A27 (humkv325), L6 (Vg), L2 (humkv328), and A3 and/or A19. N additions and P nucleotides were quite common and found in 32% and 21% of the sequences, respectively. Extended CDR3s more than nine residues in length were found in 18% of the sequences, and in 71% of cases this was due to insertion of an extra proline residue. This proline was usually explained from the germ-line sequences involved. These results are in good agreement with those of previous repertoire studies using potentially V-gene-biased techniques. Thus, it is clear that restricted V-gene usage, common N and P additions, and extended CDR3 regions are normal features and not, as has been claimed, characteristics of pathological autoantibodies.

Autoantibodies↗
PubMed1997

Mannan-binding lectin in the sub-Saharan HIV and tuberculosis epidemics.

Inherited deficiency of mannan-binding lectin (MBL) has been shown to predispose to infections. Conversely, it has also been suggested that MBL might facilitate the uptake of certain intracellular microbes. The aim of this study was to investigate whether MBL plays a role in the HIV and tuberculosis epidemics in Africa. Thus, the authors determined the MBL serum concentration in 173 HIV infected patients (150 with concomitant tuberculosis), 94 patients with tuberculosis without being HIV infected, and 113 controls from Tanzania. The frequency of MBL deficiency was significantly increased in HIV infected patients compared with controls (12.1% and 3.5%, respectively). The frequency of patients deficient of MBL did not differ between controls and HIV negative patients with tuberculosis. However, HIV negative patients with tuberculosis had significantly higher MBL levels than both controls and HIV infected patients with or without tuberculosis. These results indicate that low levels of MBL are associated with increased risk of sexually transmitted HIV infection in Africans. By contrast, high levels of MBL may be involved in the pathogenesis of tuberculosis in immunocompetent individuals.

Adolescent↗
PubMed1997

Platelet alloimmunization after transfusion. A prospective study in 117 heart surgery patients.

BACKGROUND AND OBJECTIVES: The frequency of platelet-specific antibodies after one series of blood transfusions has not been reported, and in multiply transfused patients is controversial. MATERIALS AND METHODS: We studied the frequency of alloimmunization against platelet antigens in 117 patients who received a single series of blood transfusions. They received mostly saline-adenine-glucose+mannitol red blood cell components (poor in leukocytes and platelets) in connection with cardiac surgery. Platelet-specific antibodies were detected with the platelet ELISA and the monoclonal-antibody-specific immobilization of platelet antigen assay. HLA antibodies were detected by the standard lymphocyte cytotoxicity techniques. RESULTS: We found platelet-specific anti-HPA-5b (anti-Bra) in 2 cases (1.7%). One antibody was the result of de novo immunization. We detected lymphocytotoxic HLA antibodies in 21 patients (17.9%), of whom 18 (15.4%) had had no detectable antibodies before transfusion. There was a positive correlation between the transfused load of immunogenic materials and the frequency of alloimmunization against HLA antigens. In one third of the immunized patients, there was no history of previous immunization. CONCLUSION: There was a low incidence of platelet-specific antibodies after one series of blood transfusions in this group of patients. This is similar to the results of some previous studies in multiply transfused patients, but not with those of others who found a higher incidence.

Adolescent↗
PubMed1997

Heterozygosity for a deletion in the CKR-5 gene leads to prolonged AIDS-free survival and slower CD4 T-cell decline in a cohort of HIV-seropositive individuals.

OBJECTIVE: Recently, it has been shown that a homozygous 32 base-pair deletion in the gene encoding CKR-5, a major coreceptor for HIV-1, leads to resistance to infection with HIV-1. We have investigated whether HIV-seropositive individuals who were heterozygous for the CKR-5 deletion had a different course of the disease. DESIGN: Thirty-five high-risk HIV-seronegative and 99 HIV-seropositive Danish homosexual men followed form 1985 to 1996 and 37 blood donors were analysed for their CKR-5 genotype by polymerase chain reaction. RESULTS: Two (6%) of the 35 HIV-seropositive subjects at high-risk of infection were homozygous and seven (20%) were heterozygous for the CKR-5 deletion. This was not significantly different from the distribution in normal donors. Twenty-two (22%) of the 99 HIV-seropositive subjects were heterozygous and none was homozygous. Two subgroups of patients who had an opposite course of the HIV disease were identified. Of nine long-term non-progressors, six (66%) were heterozygous for the deletion. This frequency is significantly higher than in nine rapid progressors of whom non was heterozygous. The frequency of heterozygotes in long-term non-progressors was also significantly higher than in the cohort as a whole. A Kaplan-Meier plot of the HIV-seropositive subjects, of whom 57 developed AIDS, showed a significantly better prognosis within the first 7 years of follow-up for those who were heterozygous for the deletion. Heterozygous individuals also had a significantly slower decrease in CD4 T-cell count per year. CONCLUSION: Individuals who are heterozygous for the 32-base-pair deletion in the CKR-5 gene have a slower decrease in their CD4 T-cell count and a longer AIDS-free survival than individuals with the wild-type gene for up to 11 years of follow-up.

CD4 Lymphocyte Count↗
PubMed1997

Interleukin 2 induces a transient downregulation of protein phosphatase 1 and 2A activity in human T cells.

Stimulation of human CD4+ T cell lines with interleukin 2 (IL-2) induces tyrosine, serine and threonine phosphorylation of a series of proteins involved in the IL-2 receptor (IL-2R) signaling pathway. Here, we examined whether IL-2 induces changes in the activity of protein serine/threonine phosphatases in antigen specific, CD4+ human T cell lines. Using inhibitors of protein phosphatases 1 (PP1, PP2A, and PP2B, we provide evidence, that IL-2 induces a downregulation of PP activity in the cytoplasmic/membrane fraction. Thus, IL-2R ligation for 30 min triggers a 16 percent decrease in total PP2A activity (p < 0.0005, n = 17) and a seven percent decrease in PP1 activity (p < 0.00005, n = 17). Cytokine-induced downregulation of PP2A activity reaches a maximum 60 min after IL-2R ligation, and returns to baseline levels within two hours. Downregulation of PPI activity reaches a maximum after 30 min and is largely reversed one hour after IL-2 stimulation. As determined from immunoblotting experiments using a specific anti-PP1 or anti-PP2A antibody, the amount of PPI and PP2A recovered from cytosolic/membrane fraction remains unchanged after IL-2 treatment suggesting that the drop in PP1/PP2A activity might be due to a regulatory change rather than to a change in the amount of PP1 and PP2A. In conclusion, we provide evidence, for the first time, that IL-2 induces a transient downregulation of PP2A activity in T cells. In addition, our findings indicate that cytoplasmic PP1 activity is transiently downregulated following IL-2R ligation in antigen-specific, human CD4+ T cells.

CD4-Positive T-Lymphocytes↗
PubMed1997

Sequencing-based typing of HLA-A locus using mRNA and a single locus-specific PCR followed by cycle-sequencing with AmpliTaq DNA polymerase, FS.

The large number (59) of alleles now known at the HLA-A locus is a serious challenge to the existing methods for HLA typing, including many of the DNA based methods. Here, we describe a sequencing-based typing (SBT) protocol for typing of HLA-A alleles using a single A-locus-specific PCR. This reaction amplifies an 824 base pair product from cDNA, prepared from mRNA, covering exons 1-3 and most of exon 4. This product allows identification of all possible combinations of two alleles from this locus. The sequencing strategy used for allele assignment contains several improvements compared to those previously published. The enzyme AmpliTaq DNA Polymerase, FS, used, combines high-quality sequencing, i.e. long reads, low background, and uniform peak heights making the identification of heterozygous positions very reliable in a fast and easy protocol developed by determining the optima for a number of variables. Thus, this strategy meets most of the requirements for the use of sequencing in HLA typing. Furthermore, this method is very flexible. The use of a PCR primer-pair tailed with the recognition sites for two different sequencing primers allows the application of the same sets of fluorescent-labelled sequencing primers regardless of the amplified locus. Thus, the protocol can very easily be extended to cover the B- and C-locus too, simply by adding PCR reactions specific for these loci to the protocol. Using this protocol, we investigated a total of 65 cell lines and clinical samples, many of the latter chosen from samples difficult to type by serology. Our method gave in all cases unambiguous results and proved functional for work requiring the highest resolution.

Alleles↗
PubMed1997

Population studies of the human V kappa A18 gene polymorphism in Caucasians, blacks and Eskimos. New functional alleles and evidence for evolutionary selection of a more restricted antibody repertoire.

Immunoglobulin gene polymorphisms are interesting because they reflect differences in the available antibody repertoire which may affect the susceptibility to specific infections. Until recently, the human V kappa gene, A18, was known as a nonfunctional gene only. In this study, we cloned and sequenced four apparently functional alleles and determined the gene frequencies in three well-defined populations: Danish Caucasians, eastern Greenland Eskimos and Mozambican blacks. The A18b allele that was recently described in Native American Navajos by Atkinson et al. was found in all three populations with gene frequencies of 8%, 45% and 23% in Caucasians, Eskimos and blacks, respectively. Conversely, the frequencies of the nonfunctional A18a allele were 92%, 55% and 57%. Further, three new A18 alleles, c, d, and e were found exclusively in blacks, among whom they had an total frequency of 19%. These data indicate that both the A18a and A18b alleles originated before the diversification of Africans and non-Africans 90,000 years ago, whereas the A18c, A18d and A18e alleles may have a more recent origin. The functionality of the A18b allele was documented by the demonstration of properly rearranged and somatically hypermutated A18b messenger RNA present in the blood lymphocytes of individuals carrying this allele. The expression clearly exceeded that of a known functional V gene, A2, indicating that functional A18 alleles contribute significantly to the available antibody repertoire. In this context, it is surprising that the functional A18b allele apparently has been negatively selected in the Caucasian population, among whom 85% completely lack a functional gene.

Alleles↗
PubMed1997

The HLA-DQ7 and -DQ8 associations in DR4-positive rheumatoid arthritis patients. A combined analysis of data available in the literature.

Several different lines of evidence have demonstrated that inherited susceptibility to rheumatoid arthritis (RA) is associated with the DRB1 genes encoding the HLA-DR4 and HLA-DR1 molecules. A contrasting hypothesis has recently been proposed, suggesting that, in general, the DRB1 locus is associated with protection to RA and that the RA-associated DRB1 alleles are not responsible for the primary disease association but merely permissive for the susceptibility conferred by the HLA-DQ alleles with which they are in linkage disequilibrium. We have performed a critical review of the literature on the HLA association in RA with special emphasis on studies in which both an HLA-DR and -DQ association has been investigated. Our analyses provide strong evidence against the hypothesis that HLA-DQ molecules play a major role in the general susceptibility to RA. Thus, the strongest association in rheumatoid arthritis is with DRB1 genes rather than DQB1 genes.

Alleles↗
PubMed1997

HLA class II associations in juvenile Graves' disease: indication of a strong protective role of the DRB1*0701,DQA1*0201 haplotype.

Previous studies have shown that HLA-DRB1*0301 and DQA1*0501 are associated with susceptibility to Graves' disease. Ninety Danish patients with early onset of Graves' disease and 102-192 controls were analyzed for HLA-DR and -DQ to investigate if the same associations exist in the juvenile form of Graves' disease. Both DRB1*0301 and DQA1*0501 were highly significantly increased in the patients with relative risks of 8.0 and 4.6, which are higher than those seen in adults. Stratification showed that DRB1*0301 is more strongly associated than DQA1*0501. Surprisingly, the DRB1*0701,DQA1*0201 haplotype was completely absent from this group of patients, indicating a strong protective role of this haplotype in juvenile Graves' disease.

Adolescent↗
PubMed1997

The immunodeficiency after allogeneic bone marrow transplantation in man: role of cytokines.

The effect of various cytokines including rIL-1, rIL-2, rIL-3, rIL-4, rIL-6, and growth factors including rNGF, rILGF and rEPGF on the post transplant immunodeficiency after allogeneic bone marrow transplantation was explored in 8 patients. The results show that neither cytokine alone was able to increase the proliferative capability in post transplant lymphocytes, however, when added in conjunction a significant increase in PHA driven proliferation was noted. Any significant lack of growth factors is probably not the only cause of immunodeficiency post transplant, since addition of any of these compounds did not have any influence on the lymphocyte proliferation, and so the data presented here suggest that therapeutic application of any of the investigated cytokines or growth factors to such patients is unlikely to be successful in overcoming the defects of T cell function post grafting.

Acquired Immunodeficiency Syndrome↗