PubMed Health⌕ Search

Biomedical subjects

O Lantz

Publications and source records attributed to O Lantz.

At least 19 recordsLinked to original sources
PubMed2001

Differential requirement for the transcription factor PU.1 in the generation of natural killer cells versus B and T cells.

PU.1 is a member of the Ets family of transcription factors required for the development of various lymphoid and myeloid cell lineages, but its role in natural killer (NK) cell development is not known. The study shows that PU.1 is expressed in NK cells and that, on cell transfer into alymphoid Rag2/gammac(-/-) mice, hematopoietic progenitors of PU.1(-/-) fetal liver cells could generate functional NK cells but not B or T cells. Nevertheless, the numbers of bone marrow NK cell precursors and splenic mature NK cells were reduced compared to controls. Moreover, PU.1(-/-) NK cells displayed reduced expression of the receptors for stem cell factor and interleukin (IL)-7, suggesting a nonredundant role for PU.1 in regulating the expression of these cytokine receptor genes during NK cell development. PU.1(-/-) NK cells also showed defective expression of inhibitory and activating members of the Ly49 family and failed to proliferate in response to IL-2 and IL-12. Thus, despite the less stringent requirement for PU.1 in NK cell development compared to B and T cells, PU.1 regulates NK cell differentiation and homeostasis.

Animals↗
PubMed2001

Acute rejection in the absence of cognate recognition of allograft by T cells.

We studied the effects of the indirect pathway of allograft recognition using T cells from TCR transgenic Marilyn mice, which recognize the male Ag H-Y in an I-A(b)-restricted fashion. The T cells are not alloreactive to the H-2(k) haplotype, because they are not activated when adoptively transferred into recombinase-activating gene-2(-/-) common gamma-chain(-/-) double-mutant H-2(k) male or female mice. However, skin from H-2(k) males, but not from H-2(k) females, is acutely rejected by recombinase-activating gene-2(-/-) transgenic female recipients. In vitro, Marylin spleen cells primed by H-2(k) skin grafting proliferated and secreted both IL-4 and IFN-gamma in response to H-2(k) male stimulators. However, the removal of H-2(b) APC from the responding population abolished the response. Taken together, these results show that the indirect recognition that triggers rejection in this model is due to the recognition of H-Y Ag shed from H-2(k) male allograft and presented by the recipient's own I-A(b) APC to transgenic T cells. This study demonstrates unequivocally the capacity of naive CD4(+) T cells to promote the rejection of allografts through mechanisms that involve indirect destruction of grafted tissues.

Acute Disease↗
PubMed2001

Contribution of double-negative thymic precursors to CD8alpha alpha (+) intraepithelial lymphocytes of the gut in mice bearing TCR transgenes.

Using male and female RAG(-/-) mutant mice expressing TCR transgenes specific for MHC class I- or II-presented HY peptides, we performed quantitative and phenotypic comparisons between the TCR(+) lymphocytes present in the lymphoid organs and the gut mucosa in euthymic versus athymic (nude) animals. These comparisons suggest that only a minority of the TCR(+) CD8alpha alpha (+) intraepithelial lymphocytes (IEL) of the transgenic euthymic mice originate from hematopoietic precursors acquiring a TCR in the gut wall, while a majority of these CD8alpha alpha(+) IEL appear to be of thymic origin (as were all TCR(+) CD8alpha beta (+) or CD4(+) in any location); these last cells are released from the thymus as double-negative thymocytes, which are at a more immature stage (CD44(+)CD25(+)) in female mice than in males (CD44(-)). In view of previous observations that in non-transgenic athymic mice the CD8alpha alpha (+) TCR(+) IEL populations are also markedly reduced quantitatively, the possibility of a thymic contribution to these ontogenically peculiar populations may also exist in normal mice. At which stage of differentiation such precursors might leave the thymus of normal adult mice remains to be explored.

Animals↗
PubMed2001

MIKADO: a multicentre, open-label pilot study to evaluate the antiretroviral activity and safety of saquinavir with stavudine and zalcitabine.

BACKGROUND: Since eradication of HIV is unlikely, long-term management of the disease necessitates careful evaluation of the combinations of currently available drugs to determine the most potent and useful rational sequencing of regimens. OBJECTIVE: To determine the antiretroviral efficacy and tolerability of saquinavir soft gelatin capsule (SQV-SGC) plus zalcitabine (ddC) and stavudine (d4T), as first-line treatment in HIV-infected patients. DESIGN: Multicentre, open-label, non-comparative study. PATIENTS AND METHODS: Thirty-five asymptomatic, HIV-infected adults with no prior antiretroviral treatment, a CD4 count > or =250 cells/microL and baseline > or = 5000 HIV RNA copies/mL were included in the study. Patients received SQV-SGC 1200 mg three times a day (tid), ddC 0.75 mg tid and d4T 30 or 40 mg twice a day (bid) for 24 weeks. Plasma HIV RNA, CD4 and CD8 cell counts, HIV reverse transcriptase and protease resistance genotypes, SQV plasma concentration and tolerability were evaluated. RESULTS: At baseline, median HIV RNA (interquartile range) was 4.99 (4.81-5.48) log10 copies/mL, and median CD4 count was 370 (318-504) cells/microL (n = 35). At week 24, the median decrease in HIV RNA was 3.05 (2.19-3.68) log10 copies/mL. A viral load below the level of quantification (200 copies/mL and 20 copies/mL) was achieved in 63% and 34% of patients, respectively (intent-to-treat analysis). The only mutations detected were L90M substitutions in two patients. At week 24, the median CD4 count increased (P < 0.0001), and CD8 cell counts decreased (P < 0.0001), relative to baseline. In total, there were five cases of peripheral neuropathy (14%). Mean triglyceride and cholesterol levels remained within normal ranges. CONCLUSIONS: Triple therapy with SQV-SGC plus ddC and d4T is a reasonably well tolerated regimen that markedly and rapidly reduces viral load with immunological improvement. This combination is an effective additional therapeutic option, with an efficacy that compares favourably to other triple regimens used in HIV treatment.

Adult↗
PubMed2001

Transforming growth factor-beta inhibits interleukin-10 synthesis by human monocytic cells.

Transforming growth factor-beta (TGF-beta1) enhances interleukin-10 (IL-10) synthesis by mouse monocytes/macrophages, suggesting a potential role of IL-10 in mediating some of the anti-inflammatory properties of TGF-beta1. Since differences exist between the transcriptional regulation of human and mouse IL-10, the studies reported here examined whether TGF-beta1 up-regulated IL-10 production by human monocytes/macrophages as well. Exposure of PMA-differentiated U-937 promonocytic cells to TGF-beta1 resulted in an unexpected, dose-dependent decrease in IL-10 production as assessed by specific ELISA. TGF-beta1 was effective when added at the time of the PMA stimulus or 6 hours after. In addition, TGF-beta1 suppressed induction of IL-10 by three different stimuli other than PMA. TGF-beta1 inhibition of IL-10 protein release was associated with proportional changes in IL-10 mRNA accumulation as assessed by quantitative kinetic ELISA PCR. This would result from a decrease in IL-10 gene transcription as TGF-beta1 did not affect IL-10 mRNA stability, and TGF-beta1 limited the luciferase activity in cells transfected with reporter gene constructs containing 1,308 bp of the 5' non-coding sequence of human IL-10 gene. Blocking tumour necrosis factor-alpha (TNF-alpha) with neutralizing anti-TNF-alpha antibody did not modify the response to TGF-beta1, indicating the involvement of TNF-alpha-independent mechanisms in the overall process. Thus, the present study provides the first evidence that TGF-beta1 prevents IL-10 production by human monocytic cells at a transcriptional level.

Cell Differentiation↗
PubMed2000

A NK1.1+ thymocyte-derived TCR beta-chain transgene promotes positive selection of thymic NK1.1+ alpha beta T cells.

As a consequence of the peptide specificity of intrathymic positive selection, mice transgenic for a rearranged TCR beta-chain derived from conventional alphabeta T lymphocytes frequently carry mature T cells with significant skewing in the repertoire of the companion alpha-chain. To assess the generality of such an influence, we generated transgenic (Tg) mice expressing a beta-chain derived from nonclassical, NK1.1+ alphabeta T cells, the thymus-derived, CD1. 1-specific DN32H6 T cell hybridoma. Results of the sequence analysis of genomic DNA from developing DN32H6 beta Tg thymocytes revealed that the frequency of the parental alpha-chain sequence, in this instance the Valpha14-Jalpha281 canonical alpha-chain, is specifically and in a CD1.1-dependent manner, increased in the postselection thymocyte population. In accordance, we found phenotypic and functional evidence for an increased frequency of thymic, but interestingly not peripheral, NK1.1+ alphabeta T cells in DN32H6 beta Tg mice, possibly indicating a thymic determinant-dependent maintenance. Thus, in vivo expression of the rearranged TCR beta-chain from a thymus-derived NK1.1+ Valpha14+ T cell hybridoma promotes positive selection of thymic NK1.1+ alphabeta T cells. These observations indicate that the strong influence of productive beta-chain rearrangements on the TCR sequence and specificity of developing thymocytes, which operates through positive selection on self-determinants, applies to both classical and nonclassical alphabeta T cells and therefore represents a general phenomenon in intrathymic alphabeta T lymphocyte development.

Animals↗
PubMed2000

Gamma chain required for naïve CD4+ T cell survival but not for antigen proliferation.

Lymphoid homeostasis is required to ensure immune responsiveness and to prevent immunodeficiency. As such, the immune system must maintain distinct populations of naïve T cells that are able to respond to new antigens as well as memory T cells specific to those antigens it has already encountered. Though both naïve and memory T cells reside in and traffic through secondary lymphoid organs, there is growing evidence that the two populations may be regulated differently. We show here that naïve T cell survival and memory T cell survival have different requirements for cytokines (including the interleukins IL-2, IL-4, IL-7, IL-9 and IL-15) that use the common cytokine receptor gamma chain (gamma c). Using monoclonal populations of antigen-specific CD4+ T cells, we found that naïve T cells cannot survive without gamma c, whereas memory T cells show no such requirement. In contrast, neither naïve nor gamma c-deficient memory T cells were impaired in their ability to proliferate and produce cytokines in response to in vivo antigenic stimulation. These data call into question the physiological role of gamma c-dependent cytokines as T cell growth factors and show that naïve and memory CD4+ T cell survival is maintained by distinct mechanisms.

Animals↗
PubMed1999

Cytomegalovirus retinitis in advanced HIV-infected patients treated with protease inhibitors: incidence and outcome over 2 years.

We prospectively studied the incidence of cytomegalovirus (CMV) retinitis in 93 patients treated with highly active antiretroviral therapy (HAART) containing a protease inhibitor (PI), during a median follow-up period of 24 months. The median initial CD4+ count was 22 cells/microl (range, 1-311 cells/microl), and the median plasma HIV viral load was 5.1 log10 copies/ml (range, 2.4-6.4 log10 copies/ml). The fundus was examined monthly in patients with a history of CMV retinitis or an initial CD4+ count <50 cells/microl and every 3 months in the other patients. Of patients with previously controlled CMV retinitis, 1 of 7 relapsed. In addition, 6 of 59 patients with a CD4+ count <50 cells/microl and no history of CMV retinitis before starting PI therapy developed CMV retinitis. Of them, 3 had at least one relapse during follow-up. CD4+ counts were <40 cells/microl at the time of primary or recurrent CMV retinitis, except in two cases (147 cells/microl and 203 cells/microl). In conclusion, the incidence of CMV retinitis was 0.091 per patient-year among study subjects with advanced HIV infection who were receiving HAART (95% confidence interval [CI], 0.037-0.145). The time to progression of CMV retinitis (mean, 215 days; 95% CI, 113-317 days) was longer than reported before widespread use of PIs.

AIDS-Related Opportunistic Infections↗
PubMed1999

Quantification of porcine cytokine gene expression using RT-PCR, a homologous internal control and chemiluminescence for microplate detection.

The polymerase chain reaction (PCR) has proved to be a sensitive and versatile method for the analysis of human and murine cytokine mRNA expression. This paper describes for the first time a reverse transcription-polymerase chain reaction (RT-PCR) at end-point for the quantification of five porcine cytokines: interferon (IFN)-gamma, interleukin (IL)-2, IL-4, IL-10 and IL-18. The main features of the methodology are: (1) a unique RT for all quantifications, (2) the addition of homologous DNA internal controls (IC) of equal length to the corresponding cytokine and consequently co-amplification of the target cytokine and the IC with equivalent efficacy, (3) PCR and detection of amplicons for all cytokines simultaneously, (4) cytokine quantification in relation to a housekeeping gene control (glyceraldehyde-3-phosphate dehydrogenase, GAPDH), (5) detection of the amplicons by enzyme linked immunosorbent assay (ELISA) using a chemiluminescent substrate with high sensitivity and wide dynamic range, (6) automation of the detection system for analysis of a large number of samples. This highly sensitive quantitative RT-PCR assay (able to detect 100-200 cytokines mRNA copies/75x10(3) cells) was validated on peripheral blood mononuclear cells (PBMC) from pigs infected or not with pseudorabies virus (PRV), re-stimulated in vitro by a mitogen or antigens.

Animals↗
PubMed1999

An invariant T cell receptor alpha chain defines a novel TAP-independent major histocompatibility complex class Ib-restricted alpha/beta T cell subpopulation in mammals.

We describe here a new subset of T cells, found in humans, mice, and cattle. These cells bear a canonical T cell receptor (TCR) alpha chain containing hAV7S2 and AJ33 in humans and the homologous AV19-AJ33 in mice and cattle with a CDR3 of constant length. These T cells are CD4(-)CD8(-) double-negative (DN) T cells in the three species and also CD8alphaalpha in humans. In humans, their frequency was approximately 1/10 in DN, 1/50 in CD8alpha+, and 1/6,000 in CD4(+) lymphocytes, and they display an activated/memory phenotype (CD45RAloCD45RO+). They preferentially use hBV2S1 and hBV13 segments and have an oligoclonal Vbeta repertoire suggesting peripheral expansions. These cells were present in major histocompatibility complex (MHC) class II- and transporter associated with antigen processing (TAP)-deficient humans and mice and also in classical MHC class I- and CD1-deficient mice but were absent from beta2-microglobulin-deficient mice, indicating their probable selection by a nonclassical MHC class Ib molecule distinct from CD1. The conservation between mammalian species, the abundance, and the unique selection pattern suggest an important role for cells using this novel canonical TCR alpha chain.

Amino Acid Sequence↗
PubMed1999

Persistent alterations in T-cell repertoire, cytokine and chemokine receptor gene expression after 1 year of highly active antiretroviral therapy.

OBJECTIVES: To examine T-cell repertoire modifications, the evolution of T-helper (TH)1/TH2 cytokine imbalance and modifications in chemokine receptor expression when the viral load is decreased by 2-3 log10 copies/ml under highly active antiretroviral therapy (HAART). DESIGN: Sixteen patients previously treated with zidovudine and lamivudine, with CD4 cells below 300 x 10(6)/l and viraemia above 30000 copies/ml were treated by saquinavir and ritonavir together with both reverse transcriptase (RT) inhibitors (ANRS 069 trial). T-cell repertoire, chemokine receptor and lymphokine expression were studied from peripheral blood mononuclear cells sampled at weeks 0, 24 and 48. METHODS: T-cell repertoire study was carried out using the Immunoscope method. Interleukin (IL)-12 receptor beta2, CC-chemokine receptor (CCR)-3, CXC-chemokine receptor-4 and CCR-5 expression in CD4+ cells was measured by kinetic quantitative PCR and IL-2, IL-4, IL-10, IL-13, interferon (IFN)-gamma were measured using a quantitative RT-PCR assay with homologous internal standards. RESULTS: Repertoire alterations were more frequent in CD4- than in CD4+ cells and persisted despite undetectable viraemia. Increased CCR-3 expression and spontaneous IFN-gamma as well as mitogenic induced IL-13 were observed at baseline and decreased slightly under HAART. CONCLUSION: The CD8+ cell repertoire alterations were profound, whereas the CD4+ cell alterations were moderate and both persisted unchanged under HAART. The TH1/TH2 imbalance was more related to TH2 over-expression than to TH1 deficiency and persisted for at least 1 year under HAART.

Adult↗
PubMed1999

Thymic dependence of invariant V alpha 14+ natural killer-T cell development.

Both thymic and extrathymic bone marrow (BM)-derived pathways for the development of CD1 reactive, Valpha14-Jalpha281(+) NK1.1(+) T cells have been suggested. In this report, we sought evidence for extrathymic NK-T cell development using two approaches. First, BM cells from gammac-deficient mice were examined for the presence of Valpha14-Jalpha281 transcripts. Since intrathymic NK-T cell selection is gammac independent, we predicted that gammac(-) BM cells should also harbor these specific TCRalpha chains. Second, Valpha14-Jalpha281 transcripts were analyzed in BM cells from lethally irradiated, thymectomized mice reconstituted with fetal liver hematopoietic precursors. All donor-derived T cell development in these chimeras is by definition extrathymic. In both cases, we failed to detect invariant Valpha14(+) TCRalpha chain transcripts. These experiments call into question the significance of an extrathymic pathway of development for Valpha14(+) NK1.1(+) CD1-reactive T cells.

Animals↗
PubMed1998

Overexpression of natural killer T cells protects Valpha14- Jalpha281 transgenic nonobese diabetic mice against diabetes.

Progression to destructive insulitis in nonobese diabetic (NOD) mice is linked to the failure of regulatory cells, possibly involving T helper type 2 (Th2) cells. Natural killer (NK) T cells might be involved in diabetes, given their deficiency in NOD mice and the prevention of diabetes by adoptive transfer of alpha/beta double-negative thymocytes. Here, we evaluated the role of NK T cells in diabetes by using transgenic NOD mice expressing the T cell antigen receptor (TCR) alpha chain Valpha14-Jalpha281 characteristic of NK T cells. Precise identification of NK1.1(+) T cells was based on out-cross with congenic NK1.1 NOD mice. All six transgenic lines showed, to various degrees, elevated numbers of NK1.1(+) T cells, enhanced production of interleukin (IL)-4, and increased levels of serum immunoglobulin E. Only the transgenic lines with the largest numbers of NK T cells and the most vigorous burst of IL-4 production were protected from diabetes. Transfer and cotransfer experiments with transgenic splenocytes demonstrated that Valpha14-Jalpha281 transgenic NOD mice, although protected from overt diabetes, developed a diabetogenic T cell repertoire, and that NK T cells actively inhibited the pathogenic action of T cells. These results indicate that the number of NK T cells strongly influences the development of diabetes.

Animals↗
PubMed1998

Quantitative ELISA-polymerase chain reaction at saturation using homologous internal DNA standards and chemiluminescence revelation.

In this report, we describe the development and validation of a convenient, versatile and high throughput quantitative polymerase chain reaction (PCR) method. This assay is based on the use of only one concentration of an internal homologous standard (IS) easily obtained by replacing an 18 nt specific sequence using recombinant PCR. Target and IS amplicons are quantitated at the PCR plateau phase using ELISA which includes a hybridization step with either target or IS specific probes and luminometric revelation. Luminometry allows measurement of amplicon levels without the need for serial dilutions. Experimental values were obtained by comparing their target/IS signal ratios to those of an external scale. A linear dynamic range over four orders of magnitude and good reproducibility were obtained. We used this assay to investigate variations of IL-13 mRNA expression in HIV-infected patients under highly active antiretroviral therapy. Furthermore, we also report a variant of this method using Taqman assay in the ABI PRISM 7,700 apparatus.

Cells, Cultured↗
PubMed1998

[Incidence and evaluation of viral retinitis in patients infected with the HIV virus and treated with HIV protease inhibitors].

BACKGROUND: Since the beginning of the use of HIV-Protease Inhibitors (PI) to treat HIV-infected patients, a decrease of the incidence of extraocular opportunistic infections has been observed. We studied the incidence of CMV-retinitis in patients treated with a highly active antitetroviral therapy (HAART) containing PI over a mean follow-up of 12 months. METHODS: Ninety-three HIV-infected patients treated with HAART containing PI were included. The mean initial CD4+ cell-count was 54/microliter (median: 22/microliter), and the mean plasma HIV-load was 5.46 log 10 RNA-copies/ml. Fundus examination was performed each month in case of a previously treated and controlled CMV-retinitis or if initial CD4 cells were below 50/microliter. In other patients, fundus examination was performed every 3 months. The mean follow-up was 362 days. RESULTS: Among the 7 patients with a previously treated and controlled CMV-retinitis, one experienced a progression during the study (after 163 days of PI). Among the 59 patients with CD4 cells below 50/microliter and without previous CMV-retinitis before the beginning of PI, 5 experienced a CMV-retinitis (mean delay after the onset of HAART: 141 days), including 2 with relapse. When retinitis occurred, CD4 cells were below 32/microliter except in one case (147/microliter). CONCLUSIONS: Compared to previously published reports, this study showed an increase of the time to progression of previously treated and controlled CMV-retinitis in patients treated with PI. Considering deeply immunocompromised patients (less than 50 CD4-cells/microliter), the risk of suffering from CMV-retinitis was 8.5% after 12 months of PI treatment. Longer follow-up remains necessary to confirm these results.

AIDS-Related Opportunistic Infections↗
PubMed1997

Lineage relationships and differentiation of natural killer (NK) T cells: intrathymic selection and interleukin (IL)-4 production in the absence of NKR-P1 and Ly49 molecules.

In this report, we have assessed the lineage relationships and cytokine dependency of natural killer (NK) T cells compared with mainstream TCR-alphabeta T cells and NK cells. For this purpose, we studied common gamma chain (gamma c)-deficient mice, which demonstrate a selective defect in CD3- NK cell development relative to conventional TCR-alphabeta T cells. NK thymocytes differentiate in gamma c- mice as shown by the normal percentage of TCR Vbeta8+ CD4-CD8- cells and the normal quantity of thymic Va14-Jalpha281 mRNA that characterize the NK T repertoire. However, gamma c-deficient NK thymocytes fail to coexpress the NK-associated markers NKR-P1 or Ly49, yet retain characteristic expression of the cytokine receptors interleukin (IL)-7R alpha and IL-2Rbeta. Despite these phenotypic abnormalities, gamma c- NK thymocytes could produce normal amounts of IL-4. These results define a maturational progression of NK thymocyte differentiation where intrathymic selection and IL-4-producing capacity can be clearly dissociated from the acquisition of the NK phenotype. Moreover, these data suggest a closer ontogenic relationship of NK T cells to TCR-alphabeta T cells than to NK cells with respect to cytokine dependency. We also failed to detect peripheral NK T cells in these mice, demonstrating that gamma c-dependent interactions are required for export and/or survival of NK T cells from the thymus. These results suggest a stepwise pattern of differentiation for thymically derived NK T cells: primary selection via their invariant TCR to confer the IL-4-producing phenotype, followed by acquisition of NK-associated markers and maturation/export to the periphery.

Animals↗
PubMed1997

Human immunodeficiency virus gp120 inhibits interleukin-12 secretion by human monocytes: an indirect interleukin-10-mediated effect.

Interleukin-12 (IL-12), a cytokine with in vitro and in vivo immunomodulatory effects, is produced mostly by activated monocytes and macrophages. To study the effect of human immunodeficiency virus (HIV) infection on IL-12 production, we investigated the expression of IL-12 at mRNA and protein levels by human monocytes preincubated with HIV-gp120. In these conditions, we show that monocytes have a decreased ability to express IL-12 mRNA subunits and to produce IL-12 p40 and bioactive p70 proteins in response to Staphylococcus aureus strain cowan I (SAC). We showed that in human monocyte cultures, HIV-gp120 induces a significant IL-10 synthesis, which in turn inhibits IL-12 subunits mRNA accumulation and protein secretion after SAC-activation. Similar data were obtained with human macrophages. These results suggest that, during HIV infection, gp120 induces in uninfected monocytes and macrophages IL-10/IL-12 disregulation, which can alter immune response.

HIV Envelope Protein gp120↗