Line D1 Research Articles

ПРИХОВАНІ ПРОЯВИ ЕФЕКТУ ПАШЕНА – БАКА В ЛІНІЯХ D1 і D2 У СПЕКТРІ СОНЯЧНОЇ ПЛЯМИ БЕЗ СПАЛАХІВ

The results of measurements of the magnetic splittings of the D1, D2, and Ni I 5892.9 Å lines in the spectrum of the sunspot on July 24, 2023, in which there were no solar flares at the time of observation, are given. The observational material was obtained with the Echelle spectrograph of the horizontal solar telescope of the Astronomical Observatory of Taras Shevchenko Kyiv National University. It turned out that in some locations of the sunspot, the measured spliting of the specified lines are practically the same, and in others they are significantly different. This indicates the inhomogeneity of the magnetic field, because with a uniform field, these splitting should differ everywhere by the same amount, depending on the Lande factors of these lines. If we assume that these factors correspond to LS coupling for all lines, then we have the following contradiction: the photospheric line NiI 5892.9 Å shows a magnetic field intermediate in magnitude between lines D1 and D2. Physically, this is unreal in the case of a uniform magnetic field; if the magnetic field weakens with height, then the nickel line should show a stronger field than both sodium lines. More realistic estimates of the magnetic field are obtained with empirical Lande factors for lines D1 and D2, corresponding to the Paschen-Back effect in these lines. However, even in this case, line D2 with a smaller Lande factor (gemp = 1.22) shows a stronger measured magnetic field in some places of the spot than line D1 with a larger Lande factor (gemp = 1.36). This is possible when the local magnetic fields in the studied spot were much stronger than according to direct measurements. Evaluation of such fields can be carried out on the basis of modeling by the “line ratio” method, which is planned to be done in the next study.

Влияние дополнительной имплантации ионов кислорода на дислокационную люминесценцию кремния, содержащего кислородные преципитаты

Dislocation-related photoluminescence is studied in unimplanted and implanted with oxygen ions silicon wafers after multistage heat treatment, used for the formation of internal getter in microelectronics, and final annealing at 1000°С in a chlorine-containing atmosphere. In unimplanted sample, the dislocation-related luminescence line D1 dominates and its intensity is more than one order of magnitude in comparison with another dislocation-related luminescence line D2. With increasing temperature, an intensity of the D1 line increases and then decreases. In implanted sample, the intensities of the D1 and D2 lines increase. For both the lines, temperature quenching of their intensities is observed only. The energies of quenching and increase of the intensities of dislocation-related photoluminescence lines are determined. Possible reasons of observed effects are discussed.

Arming oncolytic reovirus with GM-CSF gene to enhance immunity.

Oncolytic reovirus administration has been well tolerated by cancer patients in clinical trials. However, its anti-cancer efficacy as a monotherapy remains to be augmented. We and others have previously demonstrated the feasibility of producing replication-competent reoviruses expressing a heterologous transgene. Here, we describe the production of recombinant reoviruses expressing murine (mm) or human (hs) GM-CSF (rS1-mmGMCSF and rS1-hsGMCSF, respectively). The viruses could be propagated up to 10 passages while deletion mutants occurred only occasionally. In infected cell cultures, the secretion of GM-CSF protein (up to 481 ng/106 cells per day) was demonstrated by ELISA. The secreted mmGM-CSF protein was functional in cell culture, as demonstrated by the capacity to stimulate the survival and proliferation of the GM-CSF-dependent dendritic cell (DC) line D1, and by its ability to generate DCs from murine bone marrow cells. Importantly, in a murine model of pancreatic cancer we found a systemic increase in DC and T-cell activation upon intratumoral administration of rS1-mmGMCSF. These data demonstrate that reoviruses expressing functional GM-CSF can be generated and have the potential to enhance anti-tumor immune responses. The GM-CSF reoviruses represent a promising new agent for use in oncolytic virotherapy strategies.

IL-7-induced phosphorylation of the adaptor Crk-like and other targets

IL-7 is required for T cell differentiation and mature T cell homeostasis and promotes pro-B cell proliferation and survival. Tyrosine phosphorylation plays a central role in IL-7 signaling. We identified by two-dimensional electrophoresis followed by anti-phosphotyrosine immunoblotting and mass spectrometry sixteen tyrosine phosphorylated proteins from the IL-7-dependent cell line D1. IL-7 stimulation induced the phosphorylation of the proteins STI1, ATIC and hnRNPH, involved in pathways related to survival, proliferation and gene expression, respectively, and increased the phosphorylation of CrkL, a member of a family of adaptors including the highly homologous Crk isoforms CrkII and CrkI, important in multiple signaling pathways. We observed an increased phosphorylation of CrkL in murine pro-B cells and in murine and human T cells. In addition, IL-7 increased the association of CrkL with the transcription factor Stat5, essential for IL-7 pro-survival activity. The selective tyrosine kinase inhibitor Imatinib. counteracted the IL-7 pro-survival effect in D1 cells and decreased CrkL phosphorylation. These data suggested that CrkL could play a pro-survival role in IL-7-mediated signaling. We observed that pro-B cells also expressed, in addition to CrkL, the Crk isoforms CrkII and CrkI and therefore utilized pro-B cells conditionally deficient in all three to evaluate the role of these proteins. The observation that the IL-7 pro-survival effect was reduced in Crk/CrkL conditionally-deficient pro-B cells further pointed to a pro-survival role of these adaptors. To further evaluate the role of these proteins, gene expression studies were performed in Crk/CrkL conditionally-deficient pro-B cells. IL-7 decreased the transcription of the receptor LAIR1, which inhibits B cell proliferation, in a Crk/CrkL-dependent manner, suggesting that the Crk family of proteins may promote pro-B cell proliferation. Our data contribute to the understanding of IL-7 signaling and suggest the involvement of Crk family proteins in pathways promoting survival and proliferation.

Female and male orbit asymmetry: Digital analysis.

Standard anthropometric methods applied to measurements of the skull differentials are laden with mistakes stemming from the way the measuring devices are built and from a lack of experience on the part of the researchers. To increase objectivity, digital imaging measurements via computer systems were introduced. The aim of this research was to assess the asymmetry of the male and female orbit with the application of the new graphic methods: raster graphics and vector graphics. The examination was conducted on 184 well-preserved skulls. The photos were taken by a digital camera with high definition. Orbit asymmetry was examined by determining the distance between the centers of gravity of both orbits and the frontal median line d1 and d2. Then angles α and β were appointed. They are defined as angles between the line that runs through craniometrical points mf and ek on the right side (angle α) and on the left side (angle β), and the frontal median line at their crossing point. Distances r2 and r1, which are allocated points between the frontal median lines (LPP), were also set. Angles α and β were also analyzed while comparing the skulls of both genders. Statistically significant differences were only observed in male skulls. However, differences for both genders were noted in parameters d1 and d2. No statistically significant differences were discovered between men and women for parameters r1 and r2. The groups of women and men were merged, being treated as a population; which resulted in the conclusion that there are no statistically significant differences between these parameters. The skull's asymmetry connected to gender and the asymmetry of the right and left sides of examined craniums can be used in criminal examinations as well as in facial reconstructive surgeries.

Field resistance to Fusarium oxysporum and Verticillium dahliae in transgenic cotton expressing the plant defensin NaD1.

The plant defensin NaD1, from Nicotiana alata, has potent antifungal activity against a range of filamentous fungi including the two important cotton pathogens, Fusarium oxysporum f. sp. vasinfectum (Fov) and Verticillium dahliae. Transgenic cotton plants expressing NaD1 were produced and plants from three events were selected for further characterization. Homozygous plants were assessed in greenhouse bioassays for resistance to Fov. One line (D1) was selected for field trial testing over three growing seasons in soils naturally infested with Fov and over two seasons in soils naturally infested with V. dahliae. In the field trials with Fov-infested soil, line D1 had 2-3-times the survival rate, a higher tolerance to Fov (higher disease rank), and a 2-4-fold increase in lint yield compared to the non-transgenic Coker control. When transgenic line D1 was planted in V. dahliae-infested soil, plants had a higher tolerance to Verticillium wilt and up to a 2-fold increase in lint yield compared to the non-transgenic Coker control. Line D1 did not exhibit any detrimental agronomic features compared to the parent Coker control when plants were grown in non-diseased soil. This study demonstrated that the expression of NaD1 in transgenic cotton plants can provide substantial resistance to two economically important fungal pathogens.

Effect of ion doping on the dislocation-related photoluminescence in Si+-implanted silicon

The study is concerned with the effect of the additional implantation of Si samples with C+, O+, B+, P+, and Ge+ impurity ions followed by annealing at 800°C on the behavior of the dislocation photoluminescence line D1, induced in the samples by implantation with Si+ ions at a stabilized temperature followed by annealing in an oxidizing Cl-containing atmosphere. It is established that the intensity of the D1 line strongly depends on the type of incorporated atoms and the dose of additional implantation. An increase in the D1 line intensity is observed upon implantation with oxygen and boron; at the same time, in other cases, the D1 luminescence line is found to be quenched. The mechanisms of such behavior, specifically, the role of oxygen and its interaction with implanted impurities are discussed.

74 : IL-7R: Mutations in T-ALL and polymorphisms in autoimmunity

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy resulting from leukemic transformation of T-cell progenitors in the thymus. It accounts for approximately 15% of ALL cases in childhood and 20–25% in adults and is a leading cause of death in children. IL-7 and its receptor (IL-7R) play a critical role in normal T-cell development and homeostasis. Mutations in IL-7R were identified in 9% of pediatric T-ALL patients. These mutations usually involved insertions of three amino acids including cysteine and proline in the extracellular juxtamembrane region. WT or mutant forms of the human IL-7R (hIL-7R) from patients were retrovirally transfected into an IL-7-dependent murine thymic cell line D1. Mutant hIL-7Rs induced ligand-independent activation of the Jak-Stat and PI3K pathways, cell survival and proliferation. Notably, mutant hIL-7R-expressing D1 cells formed subcutaneous tumors in Rag1-/- mice, with substantial infiltration into various organs that are normally affected in advanced stages of T-ALL, such as bone marrow, liver, lymph nodes and spleen. Further functional assays revealed that mutant hIL-7Rs constitutive signaling required homodimerization via cysteines in the inserted sequences and downstream Jak1 activation, and was IL-7, γ c and Jak3-independent. Jak inhibitors were effective in blocking proliferation and survival of transformed cells. The hotspot for insertions lies in exon 6 in precisely the same region as a coding polymorphism regulating risk for MS and other autoimmune diseases, and we observe that this polymorphism affects strength of signaling. Our findings indicate that IL-7R mutations drive T-ALL, whereas polymorphisms that increase signaling promote autoimmunity, implicating IL-7R and Jak1 as therapeutic targets in these diseases.

Cryopreservation of avocado embryogenic cultures using the droplet-vitrification method

This work reports on the cryopreservation of embryogenic cultures of avocado (Persea americana Mill.). Three cryopreservation protocols, based either on slow cooling or vitrification, were tested using two cell lines representative for the two types of embryogenic cultures that can be obtained in this species. Significant interactions between the embryogenic line and the cryopreservation protocol were observed. The best results were obtained when applying the droplet-vitrification method with recovery rates ranging from 77.78 to 100 %. The slow freezing method gave rise to different results depending on the cell line. While 80 % recovery was recorded in line D1, low recovery levels (33.33 %) were achieved in samples from line D31. The effect of different PVS2 incubation times was also evaluated and 60 min was considered as the optimum period. The developmental stage of starting material proved to be a key factor. Explant consisting of a mixture of embryogenic calli and somatic embryos at early stages resulted in the highest recovery rates after thawing.

O023 Oncogenic IL-7R gain-of-function mutations in childhood T-ALL

Introduction T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy resulting from leukemic transformation of T-cell progenitors in the thymus. It accounts for approximately 15% of ALL cases in childhood and 20–25% in adults and is a leading cause of death in children. IL-7 and its receptor (IL-7R) play a critical role in normal T-cell development and homeostasis. Methods The IL-7R gene was sequenced in T-ALL from three cohorts. Results Mutations in IL-7R were identified in 9% of pediatric T-ALL patients. These mutations usually involved insertions of three amino acids including cysteine and proline in the extracellular juxtamembrane region. WT or mutant forms of the human IL-7R (hIL-7R) from patients were retrovirally transfected into an IL-7-dependent murine thymic cell line D1. Mutant hIL-7Rs induced ligand-independent activation of the Jak-Stat and PI3K pathways, cell survival and proliferation. Notably, mutant hIL-7R-expressing D1 cells induced subcutaneous tumors in Rag1-/- mice, with substantial infiltration into various organs that are normally affected in advanced stages of T-ALL, such as bone marrow, liver, lymph nodes and spleen. Further functional assays revealed that mutant hIL-7Rs constitutive signaling required homodimerization via cysteines in the inserted sequences and downstream Jak1 activation, and was IL-7, gc and Jak3-independent. Conclusion Our findings indicate that hIL-7R mutational activation drives T-ALL leukemogenesis and implicate IL-7R and Jak1 as therapeutic targets in T-ALL.

Photoluminescence in silicon implanted with silicon ions at amorphizing doses

Luminescent and structural properties of n-FZ-Si and n-Cz-Si implanted with Si ions at amorphizing doses and annealed at 1100°C in a chlorine-containing atmosphere have been studied. An analysis of proton Rutherford backscattering spectra of implanted samples demonstrated that an amorphous layer is formed, and its position and thickness depend on the implantation dose. An X-ray diffraction analysis revealed that defects of the interstitial type are formed in the samples upon annealing. Photoluminescence spectra measured at 78 K and low excitation levels are dominated by the dislocation-related line D1, which is also observed at 300 K. The peak position of this line, its full width at half-maximum, and intensity depend on the conduction type of Si and implantation dose. As the luminescence excitation power is raised, a continuous band appears in the spectrum. A model is suggested that explains the fundamental aspects of the behavior of the photoluminescence spectra in relation to the experimental conditions.

P53‐dependent and ‐independent components of IL‐2 mediated radioprotection in IL‐2 dependent T cell lines

Cytokines are crucial growth factors for the survival, proliferation and differentiation of hematopoictic cells. Previous studies have shown that many cytokines are radioprotective, i.e. able to rescue hematopoietic cells from radiation‐induced apoptosis. The radioprotective role of IL‐2 in IL‐2 dependent T cells and its molecular mechanism has not been well defined. We hypothesize that IL‐2 protects T cells from radiation‐induced apoptosis via up‐regulating antiapoptotic molecules and enhancing DNA repairs. It is well known that upon radiation induced double strand DNA break, cells immediately activate DNA repair machinery and initiate cell cycle arrest. Using IL‐2 dependent p53‐sufficient HT‐2 T cell line and p53‐deficient D1 cell line, we show that IL‐2 protects them from radiation‐induced apoptosis through up‐regulating antiapoptotic molecules and inducing G2 cell cycle arrest via Akt pathway. Although Akt mediated cell cycle arrest may occur independent of p53, it appears to be crucial for p53‐dependent radioprotection as inhibition of Akt activity delays successful repair of damaged DNA, which results in radiation‐induced apoptosis. Therefore, both p53‐dependent and ‐independent pathways are important for IL‐2 mediated radioprotection. This study is supported by NIH grants to YC (CA112065 and P20RR021970)

Interleukin (IL)‐7 promotes T‐cell survival by stabilization of Mcl‐1

IL‐7 is required for T‐cell development both in mouse and humans and for T‐cell homeostasis in the periphery. Some of the downstream signal transducers from the IL‐7 receptor are members of the Bcl‐2 family of proteins associated with mitochondrial apoptosis. Mcl‐1, one of the anti‐apoptotic members of Bcl‐2 family, became of particular interest when it was discovered that IL‐7 upregulates Mcl‐1 mRNA expression in T cells. This suggests that Mcl‐1 may contribute to the survival functions of IL‐7. In this study, we showed that the deficiency of T–cell development in IL‐7Rα KO mice could be rescued by reconstitution of IL‐7Rα deficient bone marrow by retrovirus expressing a mouse Mcl‐1 construct. To further investigate the molecular mechanism of IL‐7 regulation of Mcl‐1, we used an IL‐7‐dependent murine thymic cell line D1. Deprivation of IL‐7 from D1 cells or lymph node cells caused Mcl‐1 protein degradation by 6 hrs. Overexpression of Mcl‐1 protected D1 cells from the death induced by IL‐7 deprivation. Compared to intact Mcl‐1, the truncated form of Mcl‐1 (Δ375), with deletion of 375 nucleotides from its 5′end, showed more potent anti‐apoptotic activity, suggesting the 5′end of Mcl‐1 might contain regulatory domains. In human Mcl‐1 the lysine in the 5′ end of the gene was identified as the target site for ubiquitin. Based on this finding, we hypothesized that the lysine found in the mouse Mcl‐1 would share this function. To test this hypothesis, we mutated the first three lysine residues (39, 80, and 117) to alanine at mouse Mcl‐1 (Mcl 3KR) and tested its protein stability and its ability to prevent apoptosis. Mcl 3KR showed enhanced protein stability, and also provided D1 cells with more protection, compared to WT Mcl‐1, after 3 to 4 days of IL‐7 deprivation. Our findings suggest that Mcl‐1 plays an important role protection of T‐cell survival by IL‐7. IL‐7 strongly promotes Mcl‐1 stability, possible by controlling lysine‐directed ubiquitination.

Oxygen-Induced Modification of Dislocation Luminescence Centers in Silicon

Prospects for using the long-wavelength dislocation luminescence line D1 in silicon-based light-emitting diodes are considered. The standard spectral position of this line at 807 meV, rather than being canonic, depends on the morphology of the dislocation structure and the impurity environment of an individual dislocation. Data on the spectral distribution of luminescence intensity in the region of the D1 line have been analyzed in terms of the concentration of interstitial oxygen in a sample, plastic deformation parameters, and thermal treatment. The results obtained suggest that oxygen exerts a dominant effect on the spectral position of line D1 and luminescence intensity in its vicinity. It is shown that the probable structure of recombination centers can be described in terms of the donor-acceptor pair model, in which oxygen complexes serve as donors and the acceptors are structural defects in the dislocation core.

ALLOSPECIFIC T SUPPRESSOR CELLS IN RECIPIENTS OF RENAL ALLOGRAFTS

P1022 Aims: The aim of our studies was to develop a strategy for immunological monitoring of transplant recipients. We have explored the possibility that the immune responses to the graft may be down-regulated by allospecific T suppressor/regulatory cells. Methods: The patient population consisted of 34 recipients of renal allografts from living (N=17) or cadaver (N=17) donors. All patients were treated by standard immunosuppressive therapy. Transplant function was monitored by conventional methods. To assess the presence of TS in transplant recipient’s circulation CD8+CD28- T cells were obtained by first selecting the CD8+ population using CD8 Dynal beads and Detach beads and then depleting the CD8+CD28+ subset by use of anti-CD28 monoclonal antibody (mAb) coupled to Dynal beads. Donor APC consisted of CD2-depleted mononuclear cells (monocytes and B cells) from the donor blood or spleen. The CD40L expressing cell line D1.1 was used for CD40 triggering of APC. Crosslinking of CD40 molecules on stimulating APC was accomplished by incubating CD2-depleted APC with irradiated D1.1 cells for 24 hours in the presence or absence of recipient CD8+CD28- T cells. At the end of the incubation time, cultures were harvested, washed and stained with Annexin V to visualize apoptotic cells or with CD20/CD14 FITC and either CD80, CD86 or CD54 PE-conjugated mAb. A decrease of mean channel of fluorescence (MCF) by more than 10% in cultures with TS compared to cultures without was considered indicative of TS-mediated suppression of CD80, CD86 or CD54 induction. To determine whether recipient TS recognize specifically HLA class I antigens on donor APC, CD8+CD28- T cells and D1.1 cells were incubated with CD2-depleted “third party” control APC mismatched for all HLA class I antigens from the transplant donor. Results: A single TS determination was performed on these patients one to seventeen years following transplantation. Donor specific TS were found in 41% (N=14) of the patients while the remaining 59% (N=20) showed no Ts. Of the 14 patients with allospecific TS, 4 were transplanted 5 years prior to testing while the remaining 10 patients received the allograft 6 to 17 years earlier. This observation demonstrates for the first time that allospecific TS which recognize MHC class I antigens on donor APC can persist in the recipient’s circulation for 17 years or more. Mean Serum Creatinine was 1.82 ± 0.79 in patients with TS and 2.04 + 1.13 in patients without TS. The difference between the group is not statistically significant. Conclusions: Alloantigen specific CD8+ TS were detected in 41% of recipients of kidney from living or cadaver donors. The possibility that patients may have also developed CD4+ T regulatory cells is not excluded and deserves further studies.

Expression of the murine CD27 ligand CD70 in vitro and in vivo.

The interaction between TNFR family member CD27 and its ligand CD70 promotes lymphocyte expansion and effector cell formation. In humans, control of CD27 function is partly regulated by the restricted expression of CD70. We used newly developed mAbs to characterize murine (m) CD70 expression in vitro and in vivo. On resting lymphocytes and immature dendritic cells (DC), mCD70 is absent. In vitro, Ag receptor triggering induced mCD70 mRNA in T cells, but cell surface protein expression was very low. Activated B cells synthesized much higher levels of mCD70 mRNA than activated T cells and clearly expressed mCD70 at the cell surface. mCD70 cell surface expression could also be induced on the DC line D1 and on in vitro-generated murine DC upon maturation. In lymphoid organs of naive mice, virtually no mCD70-expressing cells were found, with exception of cells in the thymic medulla, which may be epithelial in origin. However, after intranasal infection with influenza virus, lung-infiltrating T cells and T and B cells in draining lymph nodes expressed mCD70 according to immunohistology. In such activated lymphocytes, mCD70 protein is largely retained intracellularly. Plasma membrane expression of mCD70 was only detectable by flow cytometry on a small proportion of lung-infiltrating T cells and peaked at the height of the primary response. Thus, expression of CD70 in the mouse is highly regulated at the transcriptional and posttranslational level. This most likely serves to limit excessive effector cell formation after antigenic stimulation.

X-ray and luminescent analysis of finely dispersed β-FeSi2 films formed in Si by pulsed ion-beam treatment

Finely dispersed β-FeSi2 films were formed by implanting Fe+ ions with an energy of 40 keV and a dose of 1×1016 cm−2 in Si single crystals, followed by nanosecond pulsed ion-beam treatment. The results of glancing incidence x-ray diffraction indicate the formation of a highly grain-oriented film consisting of inclusions of the iron disilicide phase (β-FeSi2) with a grain size of approximately 40 nm surrounded by a polycrystalline Si matrix. The photoluminescence spectroscopy data reveal that the photoluminescence signal with a peak around 1.56 µm, which is observed up to 210 K, is associated with direct interband transitions in β-FeSi2 and not with the contribution from the dislocation-induced line D1.

Separation of dislocation- and erbium-related photoluminescence by time resolved studies

The luminescence of Er in silicon occurs at 1.54 μm, which is very close to the dislocation-related PL signal in silicon known as D1. Photoluminescence decay measurements have been carried out on silicon co-implanted with Er and O. Decays were recorded using a transient capture card designed in-house, and decays over nearly three decades were routinely measured with a system response time of 10 μs. The decay transient always shows a component with a decay time of up to 1100 μs, and also a component with a much faster decay time. It is shown, that the presence of the fast decay component correlates with a broadening of the signal at 1.54 μm, indicative of radiative emission due to the dislocation-related line D1, and also with the observation in electron and optical microscopy of small extended defects.

Effect of dislocations on the photoluminescence decay of 1.54 μm emission from erbium-doped silicon

The decay of the photoluminescence at 1.54 μm from erbium-implanted silicon has been recorded over nearly three decades of intensity. Two components of the decay are observed at 7.5 K, one with a decay time constant of ∼40–160 μs, and the other with a characteristic time of between 800 and 1200 μs. It is found that the proportions of fast and slow components can vary depending upon the amount of implantation-induced damage, and this variation correlates with a broadening on the high energy side of the erbium related emission. The temperature dependence of the fastest decay is not consistent with it being due to an Auger process involving free carriers, and it is suggested that extended defects in the layers are responsible for this part of the decay curve. The broadening of the erbium line is attributed to the overlap of the dislocation-related line D1 with the erbium emission. Selective chemical etching and scanning electron microscopy show that there are extended defects present in samples with a short fast decay component.

Immature dendritic cells acquire CD8(+) cytotoxic T lymphocyte priming capacity upon activation by T helper cell-independent or -dependent stimuli.

The well defined, immature murine dendritic cell (DC) line D1 was used to study the role of DC maturation in CTL induction in vitro and in vivo. Maturation of D1 cells, characterized by markedly increased expression of MHC and costimulatory molecules, was induced by incubation with lipopolysaccharide, agonistic CD40 antibody, or specific CD4(+) T helper (Th) cells. Activated, but not immature, D1 cells efficiently primed alloreactive T cell responses in vitro. Similarly, priming of CTL immunity in vivo in CD4-depleted mice was only observed if these mice were immunized with activated D1 cells. This study provides formal evidence that activation of DCs, induced by Th-independent as well as Th-dependent stimuli, is essential for efficient induction of CTL responses.