Infiltrating Foxp3(+) regulatory T cells from spontaneously tolerant kidney allografts demonstrate donor-specific tolerance.

Foxp3(+) regulatory T cells (Tregs) have an essential role in immune and allograft tolerance. However, in both kidney and liver transplantation in humans, FOXP3(+) Tregs have been associated with clinical rejection. Therefore, the role and function of graft infiltrating Tregs have been of great interest. In the studies outlined, we demonstrated that Foxp3(+) Tregs were expanded in tolerant kidney allografts and in draining lymph nodes in the DBA/2 (H-2(d) ) to C57BL/6 (H-2(b) ) mouse spontaneous kidney allograft tolerance model. Kidney allograft tolerance was abrogated after deletion of Foxp3(+) Tregs in DEpletion of REGulatory T cells (DEREG) mice. Kidney allograft infiltrating Foxp3(+) Tregs (K-Tregs) expressed elevated levels of TGF-ß, IL-10, interferon gamma (IFN-γ), the transcriptional repressor B lymphocyte-induced maturation protein-1 (Blimp-1) and chemokine receptor 3 (Cxcr3). These K-Tregs had the capacity to transfer dominant tolerance and demonstrate donor alloantigen-specific tolerance to skin allografts. This study demonstrated the crucial role, potency and specificity of graft infiltrating Foxp3(+) Tregs in the maintenance of spontaneously induced kidney allograft tolerance.

Differential actions of urocortins on neurons of the myenteric division of the enteric nervous system in guinea pig distal colon.

BACKGROUND AND PURPOSE: Urocortins (Ucns) 1, 2 and 3 are corticotropin-releasing factor (CRF)-related neuropeptides and may be involved in neural regulation of colonic motor functions. Nevertheless, details of the neural mechanism of action for Ucns have been unclear. We have, here, tested the hypothesis that Ucns act in the enteric nervous system (ENS) to influence colonic motor behaviour. EXPERIMENTAL APPROACH: We used intracellular recording with 'sharp' microelectrodes, followed by intraneuronal injection of biocytin, and immunohistochemical localization of CRF(1) and CRF(2) receptors in guinea pig colonic tissue. KEY RESULTS: Application of Ucn1 depolarized membrane potentials and elevated excitability in 58% of AH-type and 60% of S-type colonic myenteric neurons. In most of the neurons tested, depolarizing responses evoked by Ucn-1 were suppressed by the CRF(1) receptor antagonist NBI 27914, but were unaffected by the CRF(2) receptor antagonist antisauvagine-30. The selective CRF(2) receptor agonists, Ucn2 and Ucn3, evoked depolarizing responses in 12 and 8% of the AH-type myenteric neurons, respectively, and had no effect on S-type neurons. Antisauvagine-30, but not NBI 27914, suppressed these Ucn2- and Ucn3-evoked responses. Immunohistochemical staining identified CRF(1) as the predominant CRF receptor subtype expressed by ganglion cell somas, while CRF(2)-immunoreactive neuronal somas were sparse. Ucns did not affect excitatory synaptic transmission in the ENS. CONCLUSIONS AND IMPLICATIONS: The results suggest that Ucns act as neuromodulators to influence myenteric neuronal excitability. The excitatory action of Ucn1 in myenteric neurons was primarily at CRF(1) receptors, and the excitatory action of Ucn2 and Ucn3 was at CRF(2) receptors.

Sentinel skin allograft-a reliable marker for monitoring of composite tissue transplant rejection.

Previous studies have demonstrated that composite tissue transplants such as limbs reject more slowly than skin transplants. This has led to the hypothesis that a simultaneous skin graft may act as an effective marker of limb rejection. The aim of this study was to test the predictive value of a sentinel skin graft as a marker of rejection, using a hind limb transplantation model in rats. Lewis rat recipients received hind limb transplants alone from a Brown Norway donor (control; n = 15) or combined with a full-thickness 15 cm(2) sentinel skin graft (n = 45). All animals received drug therapy (tacrolimus, mycophenolate mofetil, and prednisone) for 6 weeks; then, treatment was ceased entirely. Rejection of the skin graft and limb skin was assessed both by visual and histologic grading systems. Detectable visual rejection (grade 1) was observed earlier in the sentinel skin graft than in the limb skin (P < .0005); the clearest visual rejection (grade 2) appeared earlier in the sentinel skin graft (P < .005). The average histologic grade for early rejection of the skin graft was 1.46 and 1.08 for the limb skin (P < .05). These findings confirmed a visual and histologic delay in the rejection of limb skin compared with a distant sentinel skin graft. Skin grafts transplanted simultaneously with hind limbs may be a useful marker of early rejection.

Stimulation of the inferior olivary complex alters the distribution of the type 1 corticotropin releasing factor receptor in the adult rat cerebellar cortex.

In a previous study, it was shown that populations of climbing fibers, derived from the inferior olivary complex (IOC) contain the peptide corticotropin releasing factor (CRF) and that the expression of this peptide in climbing fibers could be modulated by the level of activity in olivary afferents. The intent of this study was to determine if there was comparable plasticity in the distribution of the type 1 CRF receptor (CRF-R1) in the cerebellum of the rat. Our results indicate that CRF-R1 was localized primarily to Purkinje cell somata and their primary dendrites and granule cells. In addition, scattered immunolabeling was present over the somata of Golgi cells, basket cells and stellate cells, as well as Bergmann glial cells and their processes. IOC stimulation for 30 min at 1 Hz increased CRF-R1 expression in molecular layer interneurons and processes of Bergmann glial cells. Little to no effect on CRF receptor distribution was observed in Purkinje cells, granule cells, or Golgi cells. IOC stimulation at 5 Hz however, increased CRF-R1 expression in the processes of Bergmann glial cells while decreasing its expression in basket, stellate and, to some extent, in Purkinje cells. The present results suggest that there is activity-dependent plasticity in CRF-R1 expression that must be considered in defining the mechanism by which the CRF family of peptides modulates activity in cerebellar circuits. The present results also suggest that the primary targets of CRF released from climbing fibers are Bergmann glial cells and interneurons in the molecular layer. Further, interneurons responded with a decrease in receptor expression following more intense levels of stimulation suggesting the possibility of internalization of the receptor. In contrast, Bergmann glial cells showed an increased expression in receptor expression. These data suggest that CRF released from climbing fibers may modulate the physiological properties of basket and stellate cells as well as having a heretofore unidentified and potentially unique effect on Bergmann glia.

Presynaptic localization of a truncated isoform of the type 2 corticotropin releasing factor receptor in the cerebellum.

It is now well established that corticotropin releasing factor is present in two major excitatory afferent systems to the cerebellum, namely climbing fibers and mossy fibers. Two major classes of corticotropin releasing factor receptors, each with unique binding characteristics, have been identified as type 1 and type 2. In this study we used an antibody made to the n-terminus of the type 2 corticotropin releasing factor receptor. Characterization of this antibody showed that it strongly labeled a protein with a molecular weight of 16-32 kDa and only faintly labels a 62-83 kDa protein. The lower molecular weight protein corresponds to the weight of a recently described truncated isoform of this receptor that is designated corticotropin releasing factor-type 2alpha-truncated isoform. We carried out transfection paradigms using corticotropin releasing factor-type 2alpha-truncated isoform constructs and confirmed that the antibody recognized the truncated isoform of the type 2 corticotropin releasing factor receptor. Further, light and electron microscopic studies were carried out in mice and rats to define the distribution of the truncated receptor. Immunoreactivity is evident in the basal region of many, but not all Purkinje cell bodies and their initial axonal segments, as well as the initial axonal segments of isolated Golgi cells, and cerebellar nuclear neurons. In addition, punctate elements in the molecular layer were immunolabeled. The localization of the receptor to the initial segment of Purkinje cells was confirmed with electron microscopy. Further, the punctate labeling in the molecular layer was localized to parallel fibers and their terminals. In conclusion, evidence has been presented to show that distinct isoforms of the corticotropin releasing factor receptor are present in the cerebellum. The complex interactions between corticotropin releasing factor and other members of the corticotropin releasing factor family of peptides with both pre- and postsynaptic receptors support a growing concept that corticotropin releasing factor plays an important role in modulating activity in cerebellar circuits and ultimately in controlling motor behavior.

Donor leukocytes combine with immunosuppressive drug therapy to prolong limb allograft survival.

Donor leukocytes administered at the time of transplantation may prolong organ allograft survival. This study examined the effectiveness of donor leukocyte injection combined with immunosuppression for limb transplantation across the strong histocompatibility barrier of a Brown Norway donor to a Lewis recipient. Eight animals received 6 x 10(7) donor leukocytes injected on the day of transplantation. From day 1, FK506 (2 mg/kg/d), mycophenolate mofetil (MMF) (15 mg/kg/d), and prednisone (0.5 mg/kg/d) were administered for 2 weeks. After week 2, prednisone and MMF were both tapered by 20% of the initial dosage per week. After week 7, the animals received only FK506 (2 mg/kg/d). From week 8, FK506 was tapered to the maintenance dose of 0.8 mg/kg/d at week 10 and was stopped on week 24. A control group of 8 animals underwent identical treatment except that the leukocyte injection was omitted. Rejection was observed in both groups during FK506 monotherapy; however, the onset of early rejection episodes was significantly later, the period for reversal of the first rejection was significantly shorter, and the dosage of FK506 at the time of rejection was significantly lower among leukocyte-treated recipients. After completion of immunosuppression, survival was modestly prolonged in the leukocyte-treated group. One animal is surviving without immunosuppression on day 234. This trial of donor leukocyte injection combined with immunosuppression in limb transplantation showed a modest, but significant, improvement in outcome.

Donor leukocytes combined with delayed immunosupressive drug therapy prolong limb allograft survival.

Donor leukocytes administered at the time of transplantation may prolong organ allograft survival. Delayed administration of calcineurin inhibitors, such as FK506 or cyclosporine, may enhance their efficacy. Herein the effectiveness of this strategy to promote limb transplant survival was investigated in the strong histocompatibility barrier of Brown-Norway donor to Lewis recipients. Donor leukocytes (6 x 10(7) intravenously) were injected on the day of transplantation followed on day 1 to 14 with mycophenolate mofetil (MMF; 15 mg/kg/d) and prednisone, (0.5 mg/kg/d) which were then tapered by 20% each week and stopped at week 7. Administration of of FK506 (2 mg/kg/d) was started on day 4 and continued for 8 weeks, then tapered for 4 weeks to a maintenance dose of 0.8 mg/kg/d, which was continued for 12 weeks (group A; n = 8). A control group (n = 8) underwent identical treatment save for donor leukocyte injection but rather commencement of FK506 on day 1. Rejection was common during FK506 tapering in both groups. However group A showed a significantly later onset, a shorter period for reversal of the first rejection, and a significantly lower dosage of FK506 at the time of rejection. After the completion of immunosuppression, rejection occurred significantly later in group A than the control group with one animal surviving without immunosuppression on day 344. This is the first trial of a donor leukocyte injection combined with delayed FK506 administration in limb transplantation, which suggested that it could produce a modest but significant improvement in outcome.

Evidence for an axonal localization of the type 2 corticotropin-releasing factor receptor during postnatal development of the mouse cerebellum.

Previous studies have described the embryonic and postnatal development of CRF, as well as the type 1 CRF receptor in the mouse cerebellum. The present immunohistochemical study localizes the cellular distribution of the type 2 CRF receptor (CRF-R2) during postnatal development of the mouse cerebellum. Western blot analysis indicates that the antibody used in this analysis recognizes both a full-length and a truncated isoform of the type 2 receptor. We propose that each isoform has a unique cellular distribution. In the present study, the postnatal (P) development (P0-P14) and cellular localization of CRF-R2 in different cell types was analyzed using PAP and double-label fluorescent immunohistochemistry; cell-specific antibodies were used to identify cells expressing CRF-R2 at different stages of postnatal development. At P0, CRF-R2 immunoreactivity was localized within the somata of Purkinje cells and migrating GABAergic interneurons. CRF-R2 was first observed in the initial axonal segments of some Purkinje cells at P5, and was evident in many Purkinje cell axon hillocks at P8. Punctate immunoreactivity is present in the molecular layer by P5 and is interpreted to be immunolabeled parallel fibers. Between P8 and P14, CRF-R2 immunostaining is present in the initial axonal segments of Golgi cells, within the internal granule cell layer. Finally, CRF-R2 is present in both radial glia in the molecular layer as well as in astrocytes in the white matter and internal granule cell layer from P5 to P14. The present results suggest that CRF-R2, both the truncated and the full-length isoforms, are present in the developing cerebellum, each with a unique cellular distribution. The immunohistochemical evidence indicates that the truncated isoform of the type 2 CRF receptor is in the axons of several different types of cerebellar cortical neurons, and suggests that CRF could play a role in cerebellar development by modulating the release of transmitters from excitatory and/or inhibitory interneurons, which in turn could directly alter the maturation of cerebellar circuits. In contrast, the binding of a ligand to the full-length isoform of CRF-R2 or to CRF-R1, both in a postsynaptic location, may have a more direct effect on regulating the responsiveness of these cells to growth factors or neurotransmitters released from afferent axons by regulating permeability of ion channels or altering second messenger systems.

Experimental limb transplantation, part III: induction of tolerance in the rigorous strain combination of Brown Norway donor to Lewis recipient.

The complete withdrawal of immunosuppressive therapy after hind-limb transplantation across a strong histocompatibility barrier (Brown-Norway to Lewis) included a low-dose combination of FK506, mycophenolate mofetil (MMF), and prednisone. MMF and prednisone were tapered and withdrawn between weeks 2 and 7. From weeks 8 to 24, Group 1 animals (n=23) had FK506 tapered; for those in Group 2 (n=11) the dose of FK506 was not changed. At week 24, FK506 was stopped. The six limb grafts in Group 1 (26%) that achieved the 1-year end-point uneventfully showed chimerism by bone marrow and skin grafting supporting the presence of donor-specific tolerance. Rejection, which was common during tapering of FK506, was reversed by salvage therapy. All limbs were rejected postwithdrawal in Group 2. This study showed that tapering of FK506 combined with salvage therapy may allow long-term survival of some transplanted limbs after complete withdrawal of immunosuppressive therapy despite a complete MHC barrier.

Frequency-dependent expression of corticotropin releasing factor in the rat's cerebellum.

Corticotropin releasing factor (CRF), localized in extrinsic afferents in the mammalian cerebellum, is defined as a neuromodulator within cerebellar circuits, and appears to be an essential element in the generation of long term depression, a proposed mechanism for motor learning. These physiological studies are based on exogenous application of CRF and do not address potential mechanisms that may influence endogenous release of the peptide. In the present study, immunohistochemistry was used to analyze changes in the lobular distribution of CRF-like immunoreactivity (LIR). In addition radioimmunoassay (RIA) was used to quantify changes in levels of the peptide in the cerebellum following stimulation of the inferior cerebellar peduncle (ICP) at 10 or 40 Hz or the inferior olivary nucleus (ION) at 1, 5, 10, or 20 Hz. Results indicate that there is a greater distribution of CRF-like-immunolabeled climbing fibers, mossy fibers, and astrocytes in all lobules of the cerebellum that is directly related to stimulation frequency. Maximal effects were elicited with 40 Hz ICP and 5-10 Hz ION stimulation. Quantitatively, the RIA studies indicate that there is a significant increase in CRF levels in the vermis, hemispheres and flocculus that correlates closely with stimulation frequency. In conclusion, stimulation of cerebellar afferents induces a significant change in the distribution and levels of CRF-LIR in climbing fibers, mossy fibers and glial cells. This suggests that the modulatory effects ascribed to CRF may influence a greater number of target neurons when levels of activity in afferent systems is increased.

Cord blood mononuclear cell cytokine responses in relation to maternal house dust mite allergen exposure.

BACKGROUND: Cord blood mononuclear cells have demonstrated specific immune responses to environmental allergens. OBJECTIVE: To establish whether the nature of this response is related to the level of maternal antenatal exposure to house dust mite (HDM) allergen and, hence, whether antenatal allergen avoidance may have a role in the prevention of allergic sensitization in children. METHODS: Children with a family history of asthma were recruited antenatally as subjects in a randomised controlled trial: the Childhood Asthma Prevention Study. HDM allergen (Der p 1) concentrations were measured in dust collected from the maternal bed at 36 weeks gestation. Cord blood mononuclear cells were stimulated in culture, separately, with phytohaemaglutinin (PHA) and HDM extract. Cytokine IL-4, IL-5, IL-10 and IFN-gamma concentrations in supernatant were measured by ELISA. mRNA signals for these cytokines were measured using RT-PCR. RESULTS: The median concentration of HDM allergen was 18.4 microg/g (interquartile range 7.3-35.3 microg/g). Median concentrations of IL-4, IL-5, IL-10 and IFN-gamma, after PHA stimulation were 4, 19, 401 and 1781 pg/mL, respectively. After HDM allergen stimulation the median concentrations were 0, 0, 20 and 14 pg/mL, respectively. The distribution of mRNA cytokine signals was similar. Neither cytokine protein concentrations nor cytokine mRNA signal levels were correlated with the concentration of HDM allergen in the mothers' beds at 36 weeks gestation. CONCLUSION: These findings do not support the view that the prevention of allergic disease in children requires the institution of HDM avoidance interventions during pregnancy.

Time course of upregulation of fibrogenic growth factors and cellular infiltration in a rodent model of chronic renal allograft rejection.

BACKGROUND: Chronic Rejection (CR) is the leading cause of renal allograft dysfunction. Upregulation of growth factors has been shown in CR but the time point at which this occurs in not known. The aim of this study was to examine the time course of upregulation of growth factors and correlate this with the macrophage and myofibroblast interstitial infiltrate. METHODS: Using a rat model of CR (F344 kidney donor to Lewis recipient), infiltration by ED1 + macrophages and proliferation of alpha-smooth muscle actin (alpha-SMA) and desmin-expressing cells was examined using immunohistochemistry. In addition, expression of mRNA for interferon-gamma (IFN-gamma), transforming growth factor-beta (TGF-beta), basic-fibroblast growth factor (b-FGF) and vascular endothelial growth factor (VEGF) was studied using a semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR) technique. Native Lewis rat kidney and Lewis-Lewis isografts were used as controls. RESULTS: Immunohistochemical staining of ED1 + cells showed a marked increase in the macrophage infiltrate of allografts compared to isografts at all time periods (P = 0.0002) peaking at weeks 8-12 after transplantation. Expression of alpha-SMA was also increased in allografts (P = 0.002). RT-PCR analysis showed that mRNA for TGF-beta was maximally upregulated in allografts in comparison to isografts at week 8 after engraftment (P = 0.05) and declined thereafter, although remained at elevated levels compared to controls. IFN-gamma and b-FGF gene expression was increased in allografts late in the post-transplantation period. CONCLUSION: Early infiltration of macrophages and production of TGF-beta1 was followed by later upregulation of fibrogenic growth factors and myofibroblasts associated with interstitial fibrosis and organ dysfunction.

Multiple carboxyl-terminal regions of the EBV oncoprotein, latent membrane protein 1, cooperatively regulate signaling to B lymphocytes via TNF receptor-associated factor (TRAF)-dependent and TRAF-independent mechanisms.

Latent membrane protein 1 (LMP1) is an EBV-encoded transforming protein that strongly mimics the B cell-activating properties of a normal cellular membrane protein, CD40. LMP1 and CD40 both associate with the cytoplasmic adapter proteins called TNFR-associated factors (TRAFs). TRAFs 1, 2, and 3 bind to a region of LMP1 that is essential for EBV to transform B lymphocytes, carboxyl-terminal activating region (CTAR) 1. However, studies of transiently overexpressed LMP1 molecules, primarily in epithelial cells, indicated that a second region, CTAR2, is largely responsible for LMP1-mediated activation of NF-kappaB and c-Jun N-terminal kinase. To better understand LMP1 signaling in B lymphocytes, we performed a structure-function analysis of the LMP1 C-terminal cytoplasmic domain stably expressed in B cell lines. Our results demonstrate that LMP1-stimulated Ig production, surface molecule up-regulation, and NF-kappaB and c-Jun N-terminal kinase activation require both CTAR1 and CTAR2, and that these two regions may interact to mediate LMP1 signaling. Furthermore, we find that the function of CTAR1, but not CTAR2, correlates with TRAF binding and present evidence that as yet unidentified cytoplasmic proteins may associate with LMP1 to mediate some of its signaling activities.

Signaling by CD40 and its mimics in B cell activation.

CD40 is a member of the growing tumor necrosis factor receptor (TNF-R) family of molecules, and has been shown to play important roles in T cell-mediated B lymphocyte activation. Ligation of B cell CD40 by CD154 expressed on activated T cells stimulates B cell proliferation, differentiation, isotype switching, upregulation of surface molecules contributing to antigen presentation, development of the germinal center, and the humoral memory response. Several distinct structural motifs in the CD40 cytoplasmic domain regulate various CD40 signaling pathways, which involve both the TNF-R associated factors (TRAFs) and additional signaling proteins, and lead to activation of kinases and transcription factors. CD40-mediated B cell activation is mimicked by several biological response modifiers, as well as by a viral oncoprotein encoded by the Epstein-Barr virus (EBV).

Snowmobile contributions to mobile source emissions in Yellowstone National Park.

Increases in the number of winter visitors to Yellowstone National Park during the past decade have raised concerns over the environmental impacts of snowmobiling in the park. During the 1998-99 season, more than 62,000 snowmobile and 1300 snow coach trips entered the park. Using the University of Denver's vehicle exhaust remote-sensing equipment, 1385 measurements of carbon monoxide (CO) and hydrocarbon (HC) emissions were collected from in-use snowmobiles at the west and south entrances to the park. Overall means of 392 +/- 4 g CO and 237 +/- 1 g HC were observed per kilogram of fuel consumed. In addition, using an ultraviolet monochromator, 460 measurements of toluene emissions were collected with a mean of 39 +/- 1 g toluene/kg of fuel. Using these data, a mobile source emissions inventory based on fuel use for Yellowstone National Park shows that snowmobiles account for 27% of the annual emissions of carbon monoxide and 77% of annual emissions of hydrocarbons using an equivalent best estimate for the summer mobile source emissions. Use of oxygenated fuels in snowmobiles was found to reduce CO emissions by 13.2 +/- 6.5% without an observed effect on HC emissions. Liquid-cooled sleds were found to have HC emissions 9.5 +/- 2.2% higher than those from fan-cooled sleds because of the increased intake and exhaust port sizes required in the larger liquid-cooled engines, which increases blowby in the 2-stroke engines.

A short course of methylprednisolone immunosuppression inhibits both rejection and spontaneous acceptance of rat liver allografts.

BACKGROUND: The effects of immunosuppressive drugs on transplant tolerance have not been extensively studied, although their effect on rejection is well established. METHODS: We examined the effects of a short course of treatment with the immunosuppressive drug methylprednisolone (MP) on the survival of PVG liver allografts in Dark Agouti (DA) recipients that accepted the livers and in Lewis recipients that rejected the livers. Infiltration of liver allografts was examined by immunohistochemical staining of liver sections, and apoptosis was measured by terminal deoxynucleotide transferase-mediated dUTP nick end labeling. RESULTS: A 5-day course of MP (days 0 to 4) led to rejection of four of six livers (mean survival time [MST] 99 days) in DA recipients compared with long-term survival (MST >100 days) in untreated animals. Delayed administration of MP (days 3 to 7) exacerbated rejection in DA recipients, and all eight animals rejected the graft (MST 68.5 days). Treatment of Lewis recipients with MP did not significantly prolong survival when administered from days 0 to 4 (MST 13 days), although delay of administration improved the outcome. Treatment from days 3 to 7 resulted in an MST of 21 days, whereas treatment from days 7 to 11 resulted in an MST of 41.5 days. MP treatment from day 3 to day 7 reduced T cells and interleukin 2 receptor-expressing cells but increased the numbers of apoptotic cells infiltrating both DA and Lewis strain allografts. CONCLUSIONS: These results show that immunosuppression with MP inhibits both spontaneous tolerance and rejection of liver allografts in a rat model and question the efficacy of administering MP to all liver allograft recipients from the time of transplantation.

B lymphocyte activation by contact-mediated interactions with T lymphocytes.

T cell dependent B lymphocyte activation requires interactions between numerous receptor-ligand pairs on the two cell types. Recently, advances have been made both in understanding how these various signals regulate B cell effector functions and in identifying many new receptor-ligand pairs that contribute to the regulation of B cell function by T lymphocytes.

Signaling through MHC class II molecules blocks CD95-induced apoptosis.

B cells are induced to express CD95 upon interaction with T cells. This interaction renders the B cells sensitive to CD95-mediated apoptosis, but ligation of proviability surface receptors is able to inhibit apoptosis induction. MHC class II is a key molecule required for Ag presentation to Th cells, productive T cell-B cell interaction, and B cell activation. We demonstrate here for the first time that MHC class II ligation also confers a rapid resistance to CD95-induced apoptosis, an affect that does not require de novo protein synthesis. Signaling through class II molecules blocks the activation of caspase 8, but does not affect the association of CD95 and Fas-associated death domain-containing protein. MHC class II ligation thus blocks proximal signaling events in the CD95-mediated apoptotic pathway.

Molecular mechanisms of CD40 signaling.

CD40, a member of the growing tumor necrosis factor receptor (TNF-R) family of molecules, functions as a transmembrane signal receptor in both hematopoietic and non-hematopoietic cell types, although its physiological roles are less well understood in the latter. Much has been learned over the past decade about the role of CD40 signaling in various cellular functions. In addition, some of the molecular events which occur subsequent to CD40 engagement have been characterized, although much remains to be understood. This review will summarize the known important biological roles of CD40, and discuss what is currently known about how CD40 signals.

The effects of altitude on heavy-duty diesel truck on-road emissions.

On-road measurements of carbon monoxide, hydrocarbons, and nitric oxide from 5772 heavy-duty diesel trucks at five locations in the United States and Europe show slightly increasing emissions with increasing altitude. The result for nitric oxide showed a statistically significant increase of 4.1 +/- 1 gNO/kg of fuel consumed/km increase in altitude. The increases for CO and HC were also statistically significant.