Aspirin and Hemocompatibility Events With a Left Ventricular Assist Device in Advanced Heart Failure: The ARIES-HM3 Randomized Clinical Trial

IMPORTANCE

Left ventricular assist devices (LVADs) enhance quality and duration of life in advanced heart failure. The burden of nonsurgical bleeding events is a leading morbidity. Aspirin as an antiplatelet agent is mandated along with vitamin K antagonists (VKAs) with continuous-flow LVADs without conclusive evidence of efficacy and safety.

OBJECTIVE

To determine whether excluding aspirin as part of the antithrombotic regimen with a fully magnetically levitated LVAD is safe and decreases bleeding.

DESIGN, SETTING, and PARTICIPANTS

This international, randomized, double-blind, placebo-controlled study of aspirin (100 mg/d) vs placebo with VKA therapy in patients with advanced heart failure with an LVAD was conducted across 51 centers with expertise in treating patients with advanced heart failure across 9 countries. The randomized population included 628 patients with advanced heart failure implanted with a fully magnetically levitated LVAD (314 in the placebo group and 314 in the aspirin group), of whom 296 patients in the placebo group and 293 in the aspirin group were in the primary analysis population, which informed the primary end point analysis. The study enrolled patients from July 2020 to September 2022; median follow-up was 14 months.

Intervention

Patients were randomized in a 1:1 ratio to receive aspirin (100 mg/d) or placebo in addition to an antithrombotic regimen.

MAIN OUTCOMES AND MEASURES

The composite primary end point, assessed for noninferiority (-10% margin) of placebo, was survival free of a major nonsurgical (>14 days after implant) hemocompatibility-related adverse events (including stroke, pump thrombosis, major bleeding, or arterial peripheral thromboembolism) at 12 months. The principal secondary end point was nonsurgical bleeding events.

RESULTS

Of the 589 analyzed patients, 77% were men; one-third were Black and 61% were White. More patients were alive and free of hemocompatibility events at 12 months in the placebo group (74%) vs those taking aspirin (68%). Noninferiority of placebo was demonstrated (absolute between-group difference, 6.0% improvement in event-free survival with placebo [lower 1-sided 97.5% CI, -1.6%]; P < .001). Aspirin avoidance was associated with reduced nonsurgical bleeding events (relative risk, 0.66 [95% confidence limit, 0.51-0.85]; P = .002) with no increase in stroke or other thromboembolic events, a finding consistent among diverse subgroups of patient characteristics.

CONCLUSIONS AND RELEVANCE

In patients with advanced heart failure treated with a fully magnetically levitated LVAD, avoidance of aspirin as part of an antithrombotic regimen, which includes VKA, is not inferior to a regimen containing aspirin, does not increase thromboembolism risk, and is associated with a reduction in bleeding events.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04069156.

Association of Angiopoetin-2 and TNF-α With Bleeding During Left Ventricular Assist Device Support: Analysis From the PREVENT Biorepository

The purpose of this study was to describe the changes in plasma levels of angiogenic and inflammatory biomarkers, specifically Ang-2 and TNF-α, in patients receiving HeartMate II (HMII) left ventricular assist device (LVAD) and correlate them with nonsurgical bleeding. It has been shown that angiopoietin-2 (Ang-2) and tissue necrosis factor-α (TNF-α) may be linked to bleeding in LVAD patients. This study utilized biobanked samples prospectively collected from the PREVENT study, a prospective, multicenter, single-arm, nonrandomized study of patients implanted with HMII. Paired serum samples were obtained in 140 patients before implantation and at 90 days postimplantation. Baseline demographics were as follows: age 57 ± 13 years, 41% had ischemic etiology, 82% male, and 75% destination therapy indication. In the 17 patients with baseline elevation of both TNF-α and Ang-2, 10 (60%) experienced a significant bleeding event within 180 days postimplant compared with 37 of 98 (38%) patients with Ang-2 and TNF-α below the mean ( p = 0.02). The hazard ratio for a bleeding event was 2.3 (95% CI: 1.2-4.6) in patients with elevated levels of both TNF-α and Ang-2. In the PREVENT multicenter study, patients with elevations in serum Angiopoietin-2 and TNF-α at baseline before LVAD implantation demonstrated increased bleeding events after LVAD implantation.

Impact of Race on Clinical Outcomes After Implantation With a Fully Magnetically Levitated Left Ventricular Assist Device: An Analysis From the MOMENTUM 3 Trial

BACKGROUND

Heart failure disproportionately affects Black patients. Whether differences among race influence outcomes in advanced heart failure with use of a fully magnetically levitated continuous-flow left ventricular assist device remains uncertain.

METHODS

We included 515 IDE (Investigational Device Exemption) clinical trial patients and 500 Continued Access Protocol patients implanted with the HeartMate 3 left ventricular assist device in the MOMENTUM 3 study (Multicenter Study of MagLev Technology in Patients Undergoing Mechanical Circulatory Support Therapy With HeartMate 3). Outcomes were compared between Black and White left ventricular assist device recipients for the primary end point of survival free of disabling stroke or reoperation to replace or remove a malfunctioning device at 2 years, overall survival, adverse events, 6-minute walk distance, and quality of life scores.

RESULTS

Of 1015 HeartMate 3 patients, 675 were self-identified as White and 285 as Black individuals. The Black patient cohort was younger, more obese and with a history of hypertension, and more nonischemic cause of heart failure, relative to the White patient group. Black and White patients did not experience a difference in the primary end point (81.1% versus 77.9%; hazard ratio, 1.08 [95% CI, 0.76-1.54], P=0.6568). Black patients were at higher risk of adverse events (calculated as events per 100 patient-years), including bleeding (75.4 versus 63.5; P<0.0001), stroke (9.5 versus 7.2; P=0.0183), and hypertension (10.1 versus 3.2; P<0.0001). The 6-minute walk distance was not different at baseline and 6 months between the groups, however, the absolute change from baseline was greater for White patients (median: +183.0 [interquartile range, 42.0-335.3] versus +163.8 [interquartile range, 42.3-315.0] meters, P=0.01). The absolute quality of life measurement (EuroQoL group, 5-dimension, 5-level instrument visual analog scale) at baseline and 6 months was better in the Black patient group, but relative improvement from baseline to 6 months was greater in White patients (median: +20.0 [interquartile range, 5.0-40.0] versus +25.0 [interquartile range, 10.0-45.0]; P=0.0298).

CONCLUSIONS

Although the survival free of disabling stroke or reoperation to replace/remove a malfunctioning device at 2 years with the HM 3 left ventricular assist device did not differ by race, Black HeartMate 3 patients experienced a higher morbidity burden and smaller gains in functional capacity and quality of life when compared with White patients. These findings require efforts designed to better understand and overcome these gaps through systematic identification and tackling of putative factors. Registration: URL: https://www.clinicaltrials.gov; Unique identifiers: NCT02224755 and NCT02892955.

Association of Clinical Outcomes With Left Ventricular Assist Device Use by Bridge to Transplant or Destination Therapy Intent: The Multicenter Study of MagLev Technology in Patients Undergoing Mechanical Circulatory Support Therapy With HeartMate 3 (MOMENTUM 3) Randomized Clinical Trial

Question

In patients with advanced heart failure, do outcomes with left ventricular assist device implantation differ by the initial intended goal of therapy as a bridge to transplant or destination therapy?

Findings

In this randomized clinical trial, the composite end point of survival free of disabling stroke or reoperation to remove or replace a malfunctioning device at 2 years was significantly better with the magnetically levitated centrifugal-flow HeartMate 3 than the mechanical-bearing axial-flow HeartMate II, irrespective of preimplant therapeutic intent. Event-free survival was not different between patients in the bridge to transplant or destination therapy groups treated with the HeartMate 3 pump.

Meaning

Per this randomized clinical trial, use of categorizations based on current or future transplant eligibility should be abandoned in favor of a single treatment indication for use of left ventricular assist devices.

Importance

Left ventricular assist devices (LVADs) are well established in the treatment of advanced heart failure, but it is unclear whether outcomes are different based on the intended goal of therapy in patients who are eligible vs ineligible for heart transplant.

Objective

To determine whether clinical outcomes in the Multicenter Study of MagLev Technology in Patients Undergoing Mechanical Circulatory Support Therapy With HeartMate 3 (MOMENTUM 3) trial differed by preoperative categories of bridge to transplant (BTT) or bridge to transplant candidacy (BTC) vs destination therapy (DT).

Design, Setting, and Participants

This study was a prespecified secondary analysis of the MOMENTUM 3 trial, a multicenter randomized clinical trial comparing the magnetically levitated centrifugal-flow HeartMate 3 (HM3) LVAD to the axial-flow HeartMate II (HMII) pump. It was conducted in 69 centers with expertise in managing patients with advanced heart failure in the United States. Patients with advanced heart failure were randomized to an LVAD, irrespective of the intended goal of therapy (BTT/BTC or DT).

Main Outcomes and Measures

The primary end point was survival free of disabling stroke or reoperation to remove or replace a malfunctioning device at 2 years. Secondary end points included adverse events, functional status, and quality of life.

Results

Of the 1020 patients with implants (515 with HM3 devices [50.5%] and 505 with HMII devices [49.5%]), 396 (38.8%) were in the BTT/BTC group (mean [SD] age, 55 [12] years; 310 men [78.3%]) and 624 (61.2%) in the DT group (mean [SD] age, 63 [12] years; 513 men [82.2%]). Of the patients initially deemed as transplant ineligible, 84 of 624 patients (13.5%) underwent heart transplant within 2 years of LVAD implant. In the primary end point analysis, HM3 use was superior to HMII use in patients in the BTT/BTC group (76.8% vs 67.3% for survival free of disabling stroke and reoperation; hazard ratio, 0.62 [95% CI, 0.40-0.94]; log-rank P = .02) and patients in the DT group (73.2% vs 58.7%; hazard ratio, 0.61 [95% CI, 0.46-0.81]; log-rank P < .001). For patients in both BTT/BTC and DT groups, there were not significantly different reductions in rates of pump thrombosis, stroke, and gastrointestinal bleeding with HM3 use relative to HMII use. Improvements in quality of life and functional capacity for either pump were not significantly different regardless of preimplant strategy.

Conclusions and Relevance

In this trial, the superior treatment effect of HM3 over HMII was similar for patients in the BTT/BTC or DT groups. It is possible that use of arbitrary categorizations based on current or future transplant eligibility should be clinically abandoned in favor of a single preimplant strategy: to extend the survival and improve the quality of life of patients with medically refractory heart failure.

Trial Registration

ClinicalTrials.gov identifier: NCT02224755

A Fully Magnetically Levitated Left Ventricular Assist Device - Final Report

BACKGROUND

In two interim analyses of this trial, patients with advanced heart failure who were treated with a fully magnetically levitated centrifugal-flow left ventricular assist device were less likely to have pump thrombosis or nondisabling stroke than were patients treated with a mechanical-bearing axial-flow left ventricular assist device.

METHODS

We randomly assigned patients with advanced heart failure to receive either the centrifugal-flow pump or the axial-flow pump irrespective of the intended goal of use (bridge to transplantation or destination therapy). The composite primary end point was survival at 2 years free of disabling stroke or reoperation to replace or remove a malfunctioning device. The principal secondary end point was pump replacement at 2 years.

RESULTS

This final analysis included 1028 enrolled patients: 516 in the centrifugal-flow pump group and 512 in the axial-flow pump group. In the analysis of the primary end point, 397 patients (76.9%) in the centrifugal-flow pump group, as compared with 332 (64.8%) in the axial-flow pump group, remained alive and free of disabling stroke or reoperation to replace or remove a malfunctioning device at 2 years (relative risk, 0.84; 95% confidence interval [CI], 0.78 to 0.91; P<0.001 for superiority). Pump replacement was less common in the centrifugal-flow pump group than in the axial-flow pump group (12 patients [2.3%] vs. 57 patients [11.3%]; relative risk, 0.21; 95% CI, 0.11 to 0.38; P<0.001). The numbers of events per patient-year for stroke of any severity, major bleeding, and gastrointestinal hemorrhage were lower in the centrifugal-flow pump group than in the axial-flow pump group.

CONCLUSIONS

Among patients with advanced heart failure, a fully magnetically levitated centrifugal-flow left ventricular assist device was associated with less frequent need for pump replacement than an axial-flow device and was superior with respect to survival free of disabling stroke or reoperation to replace or remove a malfunctioning device. (Funded by Abbott; MOMENTUM 3 ClinicalTrials.gov number, NCT02224755.).

MojoSort: a versatile nanoparticle for magnetic isolation of cells with high purity, yield, and preserved functionality (TECH2P.926)

The isolation of specific cells from a complex population is a technical challenge that researchers face very often. Several strategies have emerged over the years, including gradient centrifugation, Fluorescent Activated Cell Sorting and Magnetic Activated Cell Sorting. Magnetic labeling is the most common approach, as it constitutes a fast, reliable, and convenient method to obtain populations with high purity and yield, and the cells are suitable for downstream applications. Here we present a new type of magnetic nanoparticles that may be used with current separation methods. To illustrate the ease and utility of the system, while maintaining functionality of the isolated cells, bone marrow cells were isolated from C57BL/6 mice using magnetic particles, and characterized by flow cytometry. The cells were then differentiated towards a macrophage-like phenotype in vitro. After culture, the cells were stimulated with LPS and CpG and the activated phenotype was compared to non-stimulated cells. Surface markers analyzed include CD80, CD86 and MHC II. The supernatant was collected and screened for the presence of cytokines, such as IFN-b, GM-CSF, IL-1b, IL-12, among others. The isolated cells show a differential activation phenotype, as well as a defined cytokine profile, in accordance with the stimulation used when compared to non-stimulated cells. Thus, we validated the high quality performance of BioLegend’s new low-cost magnetic cell separation system.

Discrimination of spectrally overlapping fluorochromes using Sony Corporations’s spectral analyzer (SP6800) (TECH1P.865)

A maximum of seven colors can be separated using traditional 2-laser flow cytometers and it is required to have the necessary band pass filters to separate these fluorochromes. In addition, these systems cannot differentiate between spectrally overlapping fluorophores such as PerCP and PerCP/Cy5.5; or FITC, PE and Alexa Fluor 514® (A514). SP6800, a novel spectral analyzer from Sony Corporation uses an innovative optics system that collects all emitted light and eliminates the need for band pass filters. We performed whole blood staining using a panel of 9 markers, which included significantly overlapping fluorochromes PerCP and PerCP/Cy5.5 and A514, PE and FITC and analyzed it on the SP6800. We were able clearly identify CD56+ (PerCP/Cy5.5), CD19+ (PerCP) and CD3+ (A514) cells. Further comparison of a 7-color panel of consisting of CD3 FITC, CD56 PE, CD19 PerCP, CD8 PE/Cy7, CD16 APC, CD4 Alexa Fluor 700® and CD62L APC/Cy7 on the BD LSRFortessa™ system and SP6800 gave similar results. Our data show that the SP6800 can perform all the analysis similar to a traditional cytometer with the added feature of separating spectrally overlapping fluorophores.

Multi-color fluorescence microscopy detection of chemokine receptors using novel Brilliant Violet™-conjugated monoclonal antibodies (CCR5P.267)

BioLegend has generated a large library of high affinity antibody clones against mouse and human chemokine receptors that are validated in flow cytometry applications. They are offered as conjugates with the violet-excited Brilliant VioletTM (BVTM) fluorophores. Use of the BVTM fluorophores has greatly increased phenotypic multiplexing capabilities in flow cytometry by increasing the utility of the violet laser. Violet-excited BV421TM antibody conjugates are at least as bright as yellow/green-excited phycoerythrin (PE) and red-excited Alexa Fluor® 647 conjugates. The brightness of violet-excited BV510TM is more on par with the green-excited Alexa Fluor® 488. BV421TM and BV510TM are far brighter and more photostable than the violet-excited Alexa Fluor® 405 and Pacific BlueTM. Here, using a variety of discrete immunologic cell populations bearing different chemokine receptors, BV421TM and BV510TM are shown to also increase multiplexing capabilities and increase resolution in fluorescence microscopy applications. Elsewhere, both BV421TM and BV510TM were excited with a multiphoton laser, indicating their potential utility in deep tissue and live cell imaging applications. The results show that BV421TM- and BV510TM-conjugated monoclonal antibodies are valuable new tools for the scientist wanting to resolve multiple antigens simultaneously with fluorescence microscopy.

Sustained Treg expansion by repeated in vivo injection of anti-TNFRSF25 mAb (P4142)

FOXP3+ Tregs play key roles in maintenance of immune tolerance and autoimmune reactions. TNFRSF25 (also known as DR3) is one of the more recently discovered TNFRSF member, which is expressed by mouse Tregs, naïve CD4, CD8, NKT cells and TLR4-induced DC and macrophages. A significant Treg in vivo expansion by TNFRSF25 stimulation has been reported. Here, we show that by single dose i.p. injection of an agonistic mAb, 4C12, Treg expansion starts to be observed on day 3, reached a peak (up to 30-40% of total CD4+ T-cells) on day 5-6, and then returned to baseline (5-7%) by day 10. Upon repeated 3-day interval injections, high level (about 20%) of expanded Tregs can be sustained more than 10 days. As reported by other authors, followed by one dose 4C12 injection, the absolute number of CD8+T cells, B cells, dendritic cells and macrophages was not affected. In the in vitro study, 4C12 antibody did not significantly induce Treg expansion in CD3/CD28/IL-2 culture system. Moreover, we characterized the TNFRSF25 expanded Tregs in vivo, we found that the expression level of CD304, CD152, Helio, GARP, LAP (TGF-b1), FR4, GITR was significantly increased in comparison to the control. These data suggest that multiple injections of 4C12 can long term sustain expanded Tregs at certain level, the biological significance of Treg need to be further studied.

LAMP5 distribution in and on plasmacytoid dendritic cells (P5019)

The brain and dendritic cell (BAD)-associated lysosome-associated membrane protein (LAMP)-like molecule, also known as BAD-LAMP, c20orf103, UNC-46, is a newly identified LAMP family member, which has been recently officially designated as LAMP5. It is a transmembrane glycosylated protein localized in the ER-Golgi intermediate compartment (ERGIC). LAMP5 shares sequence and structural homology with other LAMP family members. In mouse, LAMP5 is expressed in postnatal cortical neurons of particular layers, where it is enriched in defined zones along neuronal projections. In human, like its murine homolog, LAMP5 is principally expressed in brain, and it was recently found in primary plasmacytoid dendritic cells (pDCs). However, LAMP5 expression profile and function have not been extensively studied in pDCs. By using anti-human LAMP5 monoclonal antibody (clone 124-40B), we report that LAMP5 is specifically expressed in peripheral blood pDCs which are characterized by surface expression of CD303+/CD304+/CD123+/HLA-DR+/CXCR3+/CD11c-/CD14-/CD209-, but is not expressed by GM-CSF plus FL3 or IL-4 induced monocyte-derived CD303+/CD123+/HLA-DR+/CD209+/CD14+/CXCR3dim pDCs or CD209+/CD123dim/CXCR3dim/HLA-DR+/CD11c+/CD14+ mDCs. Like other LAMP members, LAMP5 is rapidly relocated on the cell surface of peripheral blood pDCs after 24 hours stimulation by IL-3. These data suggest that LAMP5 may be a useful marker for studying pDC development and activation.

Blocking ADP-ribosylation of cell surface proteins during cell preparation with a Nanobody against ART2 enhances chemotaxis of T cells during in vitro migration assays. (P3388)

ADP-ribosylation is the enzymatic transfer of the ADP-ribose moiety from NAD+ to a protein, a posttranslational modification that regulates the function of the targeted proteins. Although in normal conditions there is minimal extracellular NAD+, it is released from cells in inflammation and during preparation of primary lymphocytes. ART2 (CD296) is an ADP-ribosyltransferase expressed by most mature T cells, including NKT, and regulatory T cells. A major substrate for ART2 is P2X7, an ion channel that mediates shedding of CD62L, and NAD+-induced cell death (NICD). In this manner, NAD+ released during cell preparation affects the phenotype and survival of cells expressing ART2. In this study, we used a recombinant variable domain of the llama heavy-chain antibody S+16a to block the ADP-ribosyltransferase activity of ART2. The recombinant antibody was administered i.v. to mice and 1-2 h later, the CD4+ T cells from spleen and lymph nodes were isolated. The cell phenotype and functional state was analyzed by flow cytometry and chemotaxis assay respectively. A single dose of S+16a blocked the shedding of CD62L and reduced the number of apoptotic cells about 80%. The higher cell viability resulted in a 50-100% increase in the cell number responding to the chemokines CCL22 and CXCL12. We conclude that S+16a is a useful tool to protect mature T cells from NICD induced by the released NAD+ from cells during purification, thereby enhancing the efficiency of in vitro migration assays.

Expression of Ikaros family member molecules in lupus-prone mice: a preliminary analysis (P4102)

Ikaros family of zinc-finger proteins, namely Aiolos, Helios and Ikaros, are hematopoietic-specific transcription factors involved in lymphocyte development. Aiolos-deficient mice develop SLE-like disease, and Ikaros family members have been linked to the balance between T cell activation and tolerance. To begin to investigate the role of Ikaros proteins in SLE, we first determined the expression of these proteins in spleen cells of NZM.2328 mice that develop disease that mimics human SLE in many ways, including a profound female bias. Results show that Aiolos expression in T cells is significantly lower than that in B cells from NZM.2328 mice. Similar reduction in Aiolos expressing T cells was observed in old lupus-prone MRL-MpJ-Fas+/+ compared to age-matched control B6 mice. Almost all B cells expressed Aiolos in all mice tested, but the expression level was much lower in MRL-MpJ+/+ B cells than in control B6 B cells. In contrast to Aiolos expression, T cells expressing Helios were 3-4-fold higher in old NZM.2328 females than in age-matched male and younger female mice. Ikaros expression was also higher on both T and B cells in older NZM.2328 females than in age-matched male and younger female mice. Ongoing studies will investigate the relationship of dysregulated Ikaros family molecules with lupus disease and examine the role of this dysregulation in female bias and lupus pathogenesis.

GM-CSF induces podoplanin expression during dendritic cell differentiation (111.56)

Podoplanin is a mucin-type transmembrane glycoprotein containing extensive Oglycosylation in extracellular domain and two phosphorylation sites in a short cytoplasmic tail. It is expressed in kidney glomerular epithelial cells, lymphatic endothelium and subcapsular epithelial cells in murine thymus. Recently, podoplanin was found on murine F4/80 positive peritoneal macrophages and human follicular dendritic cells (FDCs) indicating that podoplanin is involved in immune response. We have reported that podoplanin is induced during Th9 and Th17 polarization. Here, we studied podoplanin expression on different types of murine myeloid cells. We found that podoplanin was not detectable on circulating and bone marrow derived neutrophils, monocytes, basophils and esinophils, its expression level on neutrophil and monocytes was not inducible followed by fMLP or TNF-a stimulation. Podoplanin was also not detectable on spleen and lymph node resided CD11b+macrophages, CD11c+ dendritic cells (cDCs) and CD8+ plasmacytoid dendritic cells (pDCs). However, podoplanin expression level has been dramatically increased on GM-CSF driven bone marrow-derived dendritic cells. These data suggest that podoplanin can be induced during GM-CSF driven dendritic cell differentiation, indicating that podoplanin may be a transient marker during dendritic cells differentiation and maturation. The mechanism of GM-CSF induced podoplanin and it significance need to be further investigated.

Role of C-type lectin receptor CLEC12A in human basophil activation (48.6)

CLEC12A is a member of the C-type lectin receptor family with a cytoplasmic immunoreceptor tyrosine-based inhibitory motif. Murine CLEC12A is expressed on variety of cell types including dendritic cells, monocytes/macrophages, B cells, neutrophils and basophils but not NK cells. In humans, CLEC12A is reported to be expressed on dendritic cells (DC, both myeloid and plasmacytoid), monocytes, B cells (normal and leukemic) and NK cells, but not on T cells or basophils. Performing flow cytometric analysis of human peripheral blood leukocytes using an anti-human CLEC12A antibody (clone 50C1), we report CLEC12A expression on a subset of CD3, CD19 and CD56 negative cells. Further analysis revealed these cells to be CCR3+ basophils. Antibody mediated ligation of CLEC12A on DCs results in cytokine production and cellular maturation and can inhibit NK cell mediated cytotoxicity. In response to IgE and IL-3, basophils can induce Th2 differentiation and amphiregulin production, respectively. We hypothesize that ligation with CLEC12A will alter IL-3 and/or IgE mediated basophil activation, which will be studied in our ongoing work.

Incidence and prevalence of CIDP and the association of diabetes mellitus

BACKGROUND

The reported prevalence of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) varies greatly, from 1.9 to 7.7 per 100,000. CIDP is reported to occur more commonly in patients with diabetes mellitus (DM) but has not been rigorously tested.

OBJECTIVES

To determine the incidence (1982-2001) and prevalence (on January 1, 2000) of CIDP in Olmsted County, Minnesota, and whether DM is more frequent in CIDP.

METHODS

CIDP was diagnosed by clinical criteria followed by review of electrophysiology. Cases were coded as definite, probable, or possible. DM was ascertained by clinical diagnosis or current American Diabetes Association glycemia criteria.

RESULTS

One thousand five hundred eighty-one medical records were reviewed, and 23 patients (10 women and 13 men) were identified as having CIDP (19 definite and 4 probable). The median age was 58 years (range 4-83 years), with a median disease duration at diagnosis of 10 months (range 2-64 months). The incidence of CIDP was 1.6/100,000/year. The prevalence was 8.9/100,000 persons on January 1, 2000. Only 1 of the 23 CIDP patients (4%) also had DM, whereas 14 of 115 age- and sex-matched controls (12%) had DM.

CONCLUSIONS

1) The incidence (1.6/100,000/year) and prevalence (8.9/100,000) of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) are similar to or higher than previous estimates. 2) The incidence of CIDP is similar to that of acute inflammatory demyelinating polyradiculoneuropathy within the same population. 3) Diabetes mellitus (DM) is unlikely to be a major risk covariate for CIDP, but we cannot exclude a small effect. 4) The perceived association of DM with CIDP may be due to misclassification of other forms of diabetic neuropathies and excessive emphasis on electrophysiologic criteria.

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Expression of the suppressor of cytokine signaling-5 (SOCS5) negatively regulates IL-4-dependent STAT6 activation and Th2 differentiation

The development of helper T (Th) cell subsets, which secrete distinct cytokines, plays an important role in determining the type of immune response. The IL-4-mediated Janus kinase-signal transducer and activator of transcription signaling pathway is crucial for mediating Th2 cell development. Notably, this pathway is selectively impaired in Th1 cells, although the molecular basis of this impairment remains unclear. We show here that during Th1 differentiation a reduction in the association of Janus kinase 1 with the IL-4 receptor (IL-4R) correlated with the appearance of the suppressor of cytokine signaling-5 (SOCS5). SOCS5 protein was preferentially expressed in committed Th1 cells and interacted with the cytoplasmic region of the IL-4Ralpha chain irrespective of receptor tyrosine phosphorylation. This unconventional interaction of SOCS5 protein with the IL-4R resulted in the inhibition of IL-4-mediated signal transducer and activator of transcription-6 activation. T cells from transgenic mice constitutively expressing SOCS5 exhibited a significant reduction of IL-4-mediated Th2 development. Therefore, the induced SOCS5 protein in Th1 differentiation environment may play an important role by regulating Th1 and Th2 balance.

Use and costs of medical care for children and adolescents with and without attention-deficit/hyperactivity disorder

CONTEXT

A shortage of data exists on medical care use by persons with attention-deficit/hyperactivity disorder (ADHD).

OBJECTIVE

To compare medical care use and costs among persons with and without ADHD.

DESIGN AND SETTING

Population-based cohort study conducted in Rochester, Minn.

SUBJECTS

All children born in 1976-1982 were followed up through 1995, using school and medical records to identify those with ADHD. The 4880 birth cohort members (mean age, 7. 3 years) still residing in Rochester in 1987 were followed up in medical facility-linked billing databases until death, emigration, or December 31, 1995.

MAIN OUTCOME MEASURES

Clinical diagnoses, likelihood and frequency of inpatient and outpatient hospitalizations, emergency department (ED) visits, and total medical costs (including ambulatory care), compared among individuals with and without ADHD.

RESULTS

Among the 4119 birth cohort members who remained in the area through 1995 (mean age, 15.3 years), 7.5% (n = 309) had met criteria for ADHD. Compared with persons without ADHD, those with ADHD were more likely to have diagnoses in multiple categories, including major injuries (59% vs 49%; P<.001) and asthma (22% vs 13%; P<.001). The proportion with any hospital inpatient, hospital outpatient, or ED admission was higher for persons with ADHD vs those without ADHD (26% vs 18% [P<. 001], 41% vs 33% [P =.006], and 81% vs 74% [P =.005], respectively). The 9-year median costs for persons with ADHD compared with those without ADHD were more than double ($4306 vs $1944; P<.001), even for the subset with no hospital or ED admissions (eg, median 1987 costs, $128 vs $65; P<.001). The differences between individuals with and without ADHD were similar for males and females and across all age groups.

CONCLUSION

In our cohort, compared with persons without ADHD, those with ADHD exhibited substantially greater use of medical care in multiple care delivery settings.

Use of nursing home after stroke and dependence on stroke severity: a population-based analysis

BACKGROUND AND PURPOSE

There are few population-based data available regarding nursing home use after stroke. This study clarifies the use of a nursing home after stroke, as well as its dependence on stroke severity, in a defined population.

METHODS

All first stroke events among residents of Rochester, Minn, during 1987-1989 were ascertained, subtyped, and assigned Rankin disability scores (RS) before the event, at maximal deficit, and at specified intervals after stroke. Persons were followed from the date of stroke event to death, emigration from Rochester, or December 31, 1994, in complete community-based medical records and Minnesota Case Mix Review Program data tapes to determine nursing home residency before stroke and at 90 days and 1 year after stroke, proportion of survival days in a nursing home, and cumulative risk of admission to a nursing home.

RESULTS

There were 251 cases of first cerebral infarction, 24 intracerebral hemorrhages, and 15 subarachnoid hemorrhages among residents of Rochester during 1987-1989. The maximal deficit RS was 1 or 2 for 62 (25%), RS 3 for 72 (29%), and RS 4 or 5 for 117 (47%) of the cerebral infarct patients. Among patients surviving to 90 days or 1 year after cerebral infarction, 25% were in nursing home at 90 days and 22% at 1 year, respectively. Within these maximal deficit RS categories, the percentages of follow-up time spent in a nursing home during the first post-cerebral infarction year are as follows: RS 1 to 2, 4%; RS 3, 10%; and RS 4 to 5, 54%. Multivariate logistic regression revealed that increasing age and RS 4 to 5 at maximal deficit were independent predictors (P<0.0001) of nursing home residency at 90 days and 1 year after stroke, whereas stroke type was not an independent predictor. At 1 year after cerebral infarction, the Kaplan-Meier estimates of proportion of people with at least 1 nursing home admission were 11% for RS 1 to 2, 22% for RS 3, and 68% for RS 4 to 5.

CONCLUSIONS

This study provides unique population-based data regarding the short- and long-term use of a nursing home after stroke and its dependence on stroke severity. More than 50% of people with a severe cerebral infarction are in a nursing home 90 days and 1 year after the stroke, and by 1 year, nearly 70% will have required some nursing home stay. Age and stroke severity are independent predictors of nursing home residency after stroke.

Identification of surrogate agonists for the human FPRL-1 receptor by autocrine selection in yeast

We describe a procedure for isolating agonists for mammalian G protein-coupled receptors of unknown function. Human formyl peptide receptor like-1 (FPRL-1) receptor, originally identified as an orphan G protein-coupled receptor related to the formyl peptide receptor (FPR1), was expressed in Saccharomyces cells designed to couple receptor activation to histidine prototrophy. Selection for histidine prototrophs among transformants obtained with a plasmid-based library encoding random peptides identified six different agonists, each of whose production yielded autocrine stimulation of the receptor expressed in yeast. A synthetic version of each peptide promoted activation of FPRL-1 expressed in human embryonic kidney (HEK293) cells, and five of the peptides exhibited significant selectivity for activation of FPRL-1 relative to FPR1. One selective peptide was tested and found to mobilize calcium in isolated human neutrophils. This demonstrates that stimulation of FPRL-1 results in neutrophil activation and suggests that the receptor functions as a component of the inflammatory response. This autocrine selection protocol may be a generally applicable method for providing pharmacological tools to evaluate the physiological roles of the growing number of mammalian orphan G protein-coupled receptors.

T-cell subset-specific expression of the IL-4 gene is regulated by a silencer element and STAT6

During development of CD4+ T lymphocytes in the periphery, differential expression of cytokine genes, such as those of interleukin (IL)-2 and IL-4, occurs in distinct T-cell subsets. IL-4 is a cytokine produced by T-helper 2 (Th2) cells, and the IL-4 receptor (IL-4R)-mediated signaling pathway is thought to be required for commitment to the Th2 phenotype. However, the molecular basis for development of the Th subset-specific production of IL-4 remains unclear. We demonstrate here that the IL-4 promoter is functional in Th1 and B cells which do not normally form IL-4 transcripts as well as in IL-4-producing T cells. Based on studies of the effect of several different upstream and downstream regions of the IL-4 gene on IL-4 promoter activity, a Th1-specific IL-4 silencer element was identified in the 3'-untranslated region. The silencer region contained a consensus sequence for a transcriptional factor that is normally regulated by the IL-4 R signaling pathway, STAT6. Nuclear expression of STAT6 protein, which was shown to bind to the silencer region, was observed in Th2 cells but not in Th1 cells. Deletion of the STAT6-binding site from the silencer region and inhibition of STAT6 function resulted in the appearance of silencing function even in Th2 cells. These results provide evidence that the silencer element, and the binding of STAT6 to this element, play a permissive role in determining the commitment into Th2 phenotype.

Free, complexed, and total serum prostate-specific antigen concentrations and their proportions in predicting stage, grade, and deoxyribonucleic acid ploidy in patients with adenocarcinoma of the prostate

OBJECTIVES

Nearly half of men with clinically localized prostate cancer are understaged. We evaluated whether knowledge of preoperative free prostate-specific antigen (f-PSA), complexed (c-PSA), and total (t-PSA) concentrations or the ratios thereof (f-PSA/t-PSA, c-PSA/t-PSA, and f-PSA/c-PSA) could improve upon the staging of prostate cancer when compared with standard PSA testing (t-PSA). In addition, we examined their associations with tumor grade and deoxyribonucleic acid (DNA) ploidy.

METHODS

Two hundred ninety patients with prostate cancer, 178 (61%) of whom were treated with radical prostatectomy, formed the study group.

RESULTS

Although there were significant differences in the f-PSA concentrations with respect to clinical stage, considerable overlap in PSA levels among the clinical substages was observed. Statistically significant differences but weak correlations were observed between the individual f-PSA, c-PSA, and t-PSA concentrations with regard to pathologic stage (organ-confined versus extraprostatic) and grade. No significant relationship, however, was observed with the three ratios. Higher PSA values were not always associated with a pathologic stage of pT3 or greater, and lower levels did not ensure that a tumor was organ-confined. Only a slight association was observed between c-PSA and t-PSA levels and DNA ploidy. No significant relationship was observed between the f-PSA levels as well as the three ratios with regard to DNA ploidy. A statistically significant improvement in predicting pathologic stage was observed when combining knowledge of preoperative t-PSA concentration with the c-PSA/t-PSA ratio. However, the area under the receiver operator characteristic curves was only slightly increased; as such this combination was of limited clinical utility.

CONCLUSIONS

Statistically significant but weak correlations were observed between the molecular forms of PSA and stage, grade, and DNA ploidy. The significant overlap in f-PSA and c-PSA values among all stages, grades, and ploidy values precluded any useful predictive information for the individual patient. As such, preoperative knowledge of f-PSA and c-PSA values and the three ratios provided no additional diagnostic information over standard PSA (t-PSA) values alone.

Fluticasone propionate aqueous nasal spray compared with terfenadine tablets in the treatment of seasonal allergic rhinitis

BACKGROUND

Comparative studies with topical corticosteroids and antihistamines for treatment of allergic rhinitis have not always demonstrated clear distinctions between the two on the basis of therapeutic efficacy.

OBJECTIVE

This study was designed to compare the efficacy and tolerability of fluticasone propionate aqueous nasal spray with those of terfenadine in the treatment of seasonal allergic rhinitis.

METHODS

Three hundred forty-eight patients with allergic rhinitis were given fluticasone propionate aqueous nasal spray (200 micrograms once daily), terfenadine tablets (60 mg twice daily), or placebo for 4 weeks in a multicenter, randomized, double-blind, double-dummy, parallel-group study.

RESULTS

Clinician-rated total nasal symptom scores after 1, 2, 3, and 4 weeks of therapy and patient-rated total nasal symptom scores throughout treatment were significantly (p <0.05) lower in the fluticasone propionate group compared with the terfenadine group or the placebo group. Terfenadine was not statistically different from placebo on the basis of clinician-related nasal symptom scores, except for sneezing. Total nasal airflow, measured by rhinomanometry, significantly (p <0.05) improved in the fluticasone propionate group compared with the terfenadine group or the placebo group. More fluticasone propionate-treated patients compared with placebo-treated patients had reduced nasal mucosal eosinophil counts after 4 weeks of therapy (p <0.05). No serious or unusual drug-related adverse events were reported. Morning plasma cortisol concentrations after 4 weeks of therapy did not differ among groups.

CONCLUSION

Fluticasone propionate aqueous nasal spray is more effective than terfenadine tablets for treatment of seasonal allergic rhinitis.

Flow cytometric ratio analysis of the Hoechst 33342 emission spectrum: multiparametric characterization of apoptotic lymphocytes

The apoptotic response to various stimuli is an important part of immune regulation, and the ability to identify apoptotic lymphocytes within a complex population is a prerequisite to a more detailed understanding of its role in vivo, We described a flow cytometric technique which utilizes viable cells and enables simultaneous identification of apoptotic cells and analyses of immunophenotype, cell cycle progression, membrane integrity and light scatter properties. It is based upon analysis of two regions of the emission spectrum of the DNA-binding vital dye hoechst 33342. We established a precise correlation between the ratio of red to blue fluorescence emission and apoptosis based upon nuclear morphology and the presence of characteristic DNA degradation patterns. In human peripheral blood lymphocytes (PBL) and mouse thymocytes we incorporated light scatter properties, cell cycle stage, relevant cell surface immunophenotypic markers (CD25 or CD4) and CD8) and a marker of plasma membrane integrity (merocyanine 540) to enable multiparametric phenotyping of apoptotic cells. We show that staurosporine-induced apoptosis of ConA-stimulated PBL is not correlated with cell cycle stage but is selective for activated cells since the frequency of large, CD25+ cells is decreased by staurosporine. Dexamethasone and ionomycin differ in their ability to induce apoptosis selectively in murine thymocyte subsets. Dexamethasone kills a broad spectrum of the CD4/8 immunophenotypes with no selectively for cell cycle stage. Ionomycin selectively deplete CD4+8+ cells, especially those in the Go/G1 region of the cell cycle, and spared CD4-8+ cells. This technique is broadly advantageous for in vitro and ex vivo models of apoptosis in that it interrogates individual viable cells and correlates membrane and nuclear apoptotic changes with standard flow cytometric immunophenotyping.

Surface mu heavy chain expressed on pre-B lymphomas transduces Ca2+ signals but fails to cause growth arrest of pre-B lymphomas

Little is known about the role of signals transduced by cell surface IgM (sIgM) expressed during early B cell development. A subclone (1.6) of the late pre-B cell lymphoma 70Z/3.12 was used to study signal transduction by surface mu heavy (H) chain before and after transition to the early immature B cell stage, and the functional consequences thereof. Although kappa L chain expression can be induced on 1.6 cells by LPS or cytokines, immunoprecipitations indicated that the non-induced 1.6 cells expressed mu H chain with an alternative protein(s) which may be a surrogate light chain(s). Consistent with this, anti-mu but not anti-kappa or anti-lambda antibodies caused transient Ca2+ mobilization in noninduced 1.6 cells. The Ca2+ signal was derived from both intracellular stores and Ca2+ influx in either noninduced cells or in cells that had been preinduced to express kappa L chain. Thus, the ability of mu H chain to mobilize Ca2+ as a second messenger does not depend upon the expression of mature L chains. The immature B lymphomas, WEHI-231 and CH1, express mature forms of IgM and undergo growth arrest when stimulated by anti-mu antibody. In contrast, signals generated by mu H chain on either noninduced or preinduced 1.6 cells or in the sIgM+ pre-B cell transfectant 300-19 mu lambda 36/8 did not cause growth arrest. These results suggest that mu H chain expressed on pre-B cells is capable of mobilizing Ca2+, but that this signal alone is insufficient to induce growth arrest in the pre-B cell.

Expression of protein kinase C isoenzymes in thymocyte subpopulations and their differential regulation

The expression of the different protein kinase C (PKC) isozymes in mouse thymocytes was studied to determine if there is a correlation between isozyme expression and thymocyte phenotype. Expression of PKC isozymes in thymocyte subsets (distinguished by the CD4 or CD8 Ag) was determined by message amplification phenotyping. The expression of mRNA for PKC-alpha, -beta, -epsilon, and -zeta, but not -gamma or -delta isozymes, was detected in all of the unstimulated thymocyte subpopulations analyzed. Thus no differences in the pattern of PKC isozyme expression were found that could be correlated with thymocyte phenotype. However, it was noted that the levels of PKC mRNA expression were affected by different stimuli in unfractionated thymocytes. Whereas mRNA levels of PKC-alpha and -beta were down-regulated by PMA and ionomycin treatment, no significant changes were seen in the levels of PKC-epsilon mRNA with these agents. PKC-epsilon mRNA decreased in thymocytes exposed to Con A similar to what has been reported for PKC-epsilon protein. PKC-zeta mRNA was also down-regulated by PMA or ionomycin, and the combination of both compounds caused a more rapid and drastic effect. Finally, PKC-delta mRNA expression was induced transiently in thymocytes only after exposure to PMA or Con A, and this induction was inhibited by ionomycin treatment. These results indicate that message levels of specific isoforms of PKC are uniquely regulated and suggest an additional level of control of PKC activity in activated lymphocytes.

Expression of protein kinase C isoenzymes in thymocyte subpopulations and their differential regulation

The expression of the different protein kinase C (PKC) isozymes in mouse thymocytes was studied to determine if there is a correlation between isozyme expression and thymocyte phenotype. Expression of PKC isozymes in thymocyte subsets (distinguished by the CD4 or CD8 Ag) was determined by message amplification phenotyping. The expression of mRNA for PKC-alpha, -beta, -epsilon, and -zeta, but not -gamma or -delta isozymes, was detected in all of the unstimulated thymocyte subpopulations analyzed. Thus no differences in the pattern of PKC isozyme expression were found that could be correlated with thymocyte phenotype. However, it was noted that the levels of PKC mRNA expression were affected by different stimuli in unfractionated thymocytes. Whereas mRNA levels of PKC-alpha and -beta were down-regulated by PMA and ionomycin treatment, no significant changes were seen in the levels of PKC-epsilon mRNA with these agents. PKC-epsilon mRNA decreased in thymocytes exposed to Con A similar to what has been reported for PKC-epsilon protein. PKC-zeta mRNA was also down-regulated by PMA or ionomycin, and the combination of both compounds caused a more rapid and drastic effect. Finally, PKC-delta mRNA expression was induced transiently in thymocytes only after exposure to PMA or Con A, and this induction was inhibited by ionomycin treatment. These results indicate that message levels of specific isoforms of PKC are uniquely regulated and suggest an additional level of control of PKC activity in activated lymphocytes.

Antigen presenting ability of thymic macrophages and epithelial cells: evidence for defects in the antigen processing function of thymic epithelial cells

We compared the antigen presenting ability of cloned thymic macrophage and epithelial cell lines using T cell hybridomas with well-characterized activation requirements. A cloned thymic epithelial cell line (3D.1), preinduced with interferon-gamma (IFN-gamma) activated the T cell hybridoma 3DO-18.3 but not the T cell hybridoma DO-11.10. Analyses using preprocessed antigen suggest that the failure of 3D.1 to activate DO-11.10 is due to its inability to process chicken ovalbumin to produce a peptide recognized by the Ag:MHC T cell receptor of DO-11.10. The epithelial cell line 3D.1 was able to activate DO-11.10 if the superantigen staphylococcal enterotoxin B was used for activation instead of ovalbumin. These observations indicate that IFN-gamma-induced 3D.1 expresses sufficient I-Ad molecules to activate DO-11.10 but is unable to produce the peptide of ovalbumin recognized by DO-11.10. Furthermore, 3D.1 appears to be representative of nonmacrophage thymic stromal cells cultured in vitro, since heterogeneous cultures containing epithelial cells exhibited the same selective T cell activation characteristics. In contrast, thymic macrophage cell lines activated all T cells studied. These results suggest that there is a functional difference between the capacity of thymic epithelial cells and macrophages to process and present antigen to T cells.

Role of interleukin-4 in T-cell ontogeny: changes in cell surface phenotype and lymphokine production of immature thymocytes after culture with interleukin-4 and phorbol ester

We have analyzed the phenotype and functional capabilities of adult and fetal CD4 8 thymocytes after 4 d of culture in IL-4 and PMA. Both adult and day 14 fetal CD4 8 thymocytes failed to acquire CD4 or CD8 antigens following culture. However, changes in expression of other antigens typical of immature thymocytes were observed. For example, the frequency with which cells expressed high levels of J11d or IL-2-R was greatly decreased following culture, whereas the frequency with which high levels of MEL-14, the lymph node homing receptor were expressed were greatly increased. This phenomenon may be due to direct induction by IL-4 and PMA of MEL-14 expression on purified MEL-14lo CD4-8- thymocytes. The frequency of cells expressing CD3, Ly-1 and Pgp-1 changed only slightly. Functionally, the cultured cells produced large amounts of interferon gamma but very little IL-2 or IL-4, although freshly isolated CD4-8- thymocytes produced all three lymphokines. These results suggest that in addition to a proliferative stimulus, culture in IL-4/PMA alters the expression of several early thymocyte antigens, the functional capabilities of CD4-8- progenitor thymocytes, and may act as a selective differentiation stimulus to MEL-14lo CD4-8- thymocytes.

Ligand-induced desensitization of B-cell membrane immunoglobulin-mediated Ca2+ mobilization and protein kinase C translocation

Binding of ligand to B-cell membrane immunoglobulin (mIg) can lead to activation of a number of distinct biologic responses, including altered expression of genes encoding c-fos, c-myc, and Ia, as well as proliferation and immunologic tolerance. Tolerance could reflect a functional uncoupling of receptors from systems that generate intracellular second messengers (i.e., receptor desensitization). To better understand the molecular basis of immune regulation, we examined the ability of mIg to function as a signal transducer after the cell's initial contact with mIg-binding ligand. The results show that ligand binding to as little as 2-10% of mIgM or mIgD renders the cell unresponsive to ligand binding to the reciprocal isotype as judged by Ca2+ mobilization and protein kinase C translocation responses. This heterologous receptor desensitization lasts longer than 24 hr and does not reflect loss of receptor from the cell surface. Studies with the calcium ionophore ionomycin, 1,2-dioctanoyl-sn-glycerol, and the protein kinase inhibitor staurosporine indicate that both protein kinase C-dependent and protein kinase C-independent (staurosporine-insensitive) mechanisms mediate heterologous desensitization after mIg crosslinking.

Up-regulation of interleukin 4 receptor expression on immature (Lyt-2-/L3T4-) thymocytes

In this report, the effect of interleukin 4 (IL-4) on the growth and differentiation of Lyt-2-/L3T4-(2-4-) thymocytes was investigated. It was found that these thymocytes proliferated extensively when cultured in the presence of IL-4 + phorbol myristate acetate without apparent differentiation to Lyt-2+ or L3T4+ cells. We also demonstrated that 2-4- thymocytes constitutively express a high affinity (dissociation constant of 20 to 40 pM) receptor for IL-4. Freshly isolated 2-4- thymocytes expressed on average about 100 IL-4 receptors per cell, but the number of receptors increased approximately 8-fold within 3 days after activation by IL-4 + phorbol myristate acetate. These findings suggest that IL-4 may play an important role in T cell ontogeny by promoting self-renewal of stem cells within the thymus.

Up-regulation of interleukin 4 receptor expression on immature (Lyt-2-/L3T4-) thymocytes

In this report, the effect of interleukin 4 (IL-4) on the growth and differentiation of Lyt-2-/L3T4-(2-4-) thymocytes was investigated. It was found that these thymocytes proliferated extensively when cultured in the presence of IL-4 + phorbol myristate acetate without apparent differentiation to Lyt-2+ or L3T4+ cells. We also demonstrated that 2-4- thymocytes constitutively express a high affinity (dissociation constant of 20 to 40 pM) receptor for IL-4. Freshly isolated 2-4- thymocytes expressed on average about 100 IL-4 receptors per cell, but the number of receptors increased approximately 8-fold within 3 days after activation by IL-4 + phorbol myristate acetate. These findings suggest that IL-4 may play an important role in T cell ontogeny by promoting self-renewal of stem cells within the thymus.

Interferon-gamma is produced by activated immature mouse thymocytes and inhibits the interleukin 4-induced proliferation of immature thymocytes

We have recently shown that interleukin 4 (IL-4) (formerly called BSF-1) is a potent stimulator of fetal and adult immature thymocyte proliferation and that adult L3T4-/Lyt-2-thymocytes can be stimulated by calcium ionophore (A23187) and phorbol ester to secrete IL-4 (Zlotnik, A., J. Ransom, G. Frank, M. Fischer, and M. Howard. 1987. Proc. Natl. Acad. Sci. (USA) 84:3856). This report shows that fetal thymocytes (day 15 of gestation) can also be activated to produce IL-4 suggesting that IL-4 may be a mediator of fetal as well as adult immature thymocyte proliferation. Furthermore, we demonstrate that interferon-gamma (IFN-gamma) inhibits the IL-4-mediated proliferation of both fetal and adult L3T4-/Lyt-2-thymocytes. The inhibition of proliferation is blocked by anti-IFN-gamma antibody and is unaffected by indomethacin suggesting that IFN-gamma directly inhibits immature thymocyte proliferation. IFN-gamma does not block the IL-4/phorbol myristate acetate-mediated proliferation of an adult thymocyte population, which is enriched for L3T4-/Lyt-2+ and L3T4+/Lyt-2- cells, suggesting that the inhibitory effect of IFN-gamma is limited to the immature thymocyte population. Both fetal (day 15) and adult L3T4-/Lyt-2--thymocytes can be activated to secrete an IFN-gamma like activity. This activity is neutralized by a monoclonal anti-IFN-gamma antibody indicating that the activity is due to IFN-gamma. mRNA analysis of adult L3T4-/Lyt-2- thymocytes stimulated with A23187 and phorbol myristate acetate confirms that mRNA for both IL-4 and IFN-gamma is induced in adult L3T4-/Lyt-2- thymocytes. These results indicate that IL-4 and IFN-gamma can regulate immature thymocyte proliferation.