A bacterium with close genetic identity to Pseudomonas mandelii associated with spring fish kills in wild bluegill Lepomis macrochirus Rafinesque and pumpkinseed sunfish Lepomis gibbosus (Linnaeus).

Pseudomonas fluorescens are known bacterial pathogens in fish. The P. fluorescens group contains at least nine different bacterial species, although species from fish have rarely been differentiated. Two isolated fish kills affecting wild bluegills, Lepomis macrochirus Rafinesque, and pumpkinseed sunfish, Lepomis gibbosus (Linnaeus), occurred in the spring of 2015 during cool water temperatures (12.5°C-15.5°C). Disease signs included severe bacteraemia with rare gross external signs. Pure bacterial cultures isolated from kidneys of all affected fish were identified as P. fluorescens using the API 20NE system, while no bacteria were isolated from asymptomatic fish. To further identify the species of bacterium within the P. fluorescens complex, genetic analysis of the 16S rRNA, rpoD and gyrB genes was conducted. DNA sequences of bacterial isolates from both mortality events were identical and had close identity (≥99.7%) to Pseudomonas mandelii. Although likely widespread in the aquatic environment, this is the first report of a bacterium closely resembling P. mandelii infecting and causing disease in fish. The bacterium grew at temperatures between 5°C and 30°C, but not at 37°C. It is possible that infections in fish were a result of immunosuppression associated with spring conditions combined with the psychrotrophic nature of the bacterium.

Spinal inhibition and motor function in adults with spastic cerebral palsy.

KEY POINTS: Abnormal activation of motoneurons in the spinal cord by sensory pathways is thought to contribute to impaired movement control and spasticity in individuals with cerebral palsy. Here we use single motor unit recordings to show how individual motoneurons in the spinal cord respond to sensory inputs in a group of participants with cerebral palsy having different degrees of motor dysfunction. In participants who had problems walking independently and required assistive devices such as wheelchairs, sensory pathways only excited motoneurons in the spinal cord. In contrast, in participants with cerebral palsy who walked independently for long distances, sensory inputs both inhibited and excited motoneurons in the spinal cord, similar to what we found in uninjured control participants. These findings demonstrate that in individuals with severe cerebral palsy, inhibitory control of motoneurons from sensory pathways is reduced and may contribute to motor dysfunction and spasticity. ABSTRACT: Reduced inhibition of spinal motoneurons by sensory pathways may contribute to heightened reflex activity, spasticity and impaired motor function in individuals with cerebral palsy (CP). To measure if the activation of inhibitory post-synaptic potentials (IPSPs) by sensory inputs is reduced in CP, the tonic discharge rate of single motor units from the soleus muscle was plotted time-locked to the occurrence of a sensory stimulation to produce peri-stimulus frequencygrams (PSFs). Stimulation to the medial arch of the foot was used to activate cutaneomuscular afferents in 17 adults with bilateral spastic CP and 15 neurologically intact (NI) peers. Evidence of IPSP activation from the PSF profiles, namely a marked pause or reduction in motor unit firing rates at the onset of the cutaneomuscular reflex, was found in all NI participants but in only half of participants with CP. In the other half of the participants with CP, stimulation of cutaneomuscular afferents produced a PSF profile indicative of a pure excitatory post-synaptic potential, with firing rates increasing above the mean pre-stimulus rate for 300 ms or more. The amplitude of motoneuron inhibition during the period of IPSP activation, as measured from the surface EMG, was less in participants with poor motor function as evaluated with the Gross Motor Functional Classification System (r = 0.72, P < 0.001) and the Functional Mobility Scale (r = -0.82, P < 0.001). These findings demonstrate that in individuals with CP, reduced activation of motoneuron IPSPs by sensory inputs is associated with reduced motor function and may contribute to enhanced reflexes and spasticity in CP.

Covert stroke after non-cardiac surgery: a prospective cohort study.

BACKGROUND: Overt stroke after non-cardiac surgery has a substantial impact on the duration and quality of life. Covert stroke in the non-surgical setting is much more common than overt stroke and is associated with an increased risk of cognitive decline and dementia. Little is known about covert stroke after non-cardiac, non-carotid artery surgery. METHODS: We undertook a prospective, international cohort study to determine the incidence of covert stroke after non-cardiac, non-carotid artery surgery. Eligible patients were ≥65 yr of age and were admitted to hospital for at least three nights after non-cardiac, non-carotid artery surgery. Patients underwent a brain magnetic resonance study between postoperative days 3 and 10. The main outcome was the incidence of perioperative covert stroke. RESULTS: We enrolled a total of 100 patients from six centres in four countries. The incidence of perioperative covert stroke was 10.0% (10/100 patients, 95% confidence interval 5.5-17.4%). Five of the six centres that enrolled patients reported an incident covert stroke, and covert stroke was found in patients undergoing major general (3/27), major orthopaedic (3/41), major urological or gynaecological (3/22), and low-risk surgery (1/12). CONCLUSIONS: This international multicentre study suggests that 1 in 10 patients ≥65 yr of age experiences a perioperative covert stroke. A larger study is required to determine the impact of perioperative covert stroke on patient-important outcomes. CLINICAL TRIAL REGISTRATION: NCT01369537.

In vivo selection using a cell-growth switch.

A major obstacle to stem-cell gene therapy rests in the inability to deliver a gene into a therapeutically relevant fraction of stem cells. One way to circumvent this obstacle is to use selection. Vectors containing two linked genes serve as the basis for selection, with one gene encoding a selectable product and the other, a therapeutic protein. Applying selection in vivo has the potential to bring a minor population of genetically corrected cells into the therapeutic range. But strategies for achieving in vivo selection have traditionally relied on genes that confer resistance to cytotoxic drugs and are encumbered by toxicity. Here we describe a new system for in vivo selection that uses a 'cell-growth switch', allowing a minor population of genetically corrected cells into the therapeutic range. But strategies for achieving in vivo selection have traditionally relied on genes that confer resistance to cytotoxic drugs and are encumbered by toxicity. Here we describe a new system for in vivo selection that uses a 'cell-growth switch', allowing a minor population of genetically modified cells to be inducibly amplified, thereby averting the risks associated with cytotoxic drugs. This system provides a general platform for conditionally expanding genetically modified cell populations in vivo, and may have widespread applications in gene and cell therapy.

Characterization of genes with a putative key role in the parasitic lifestyle of the nematode Strongyloides ratti.

Parasitic nematodes are significant pathogens of humans and other animals. The molecular and genetic basis of animal parasitism is not yet fully understood. Strongyloides spp. are a genus of gastrointestinal nematodes of which species infect approximately 100­200 million people worldwide. S. ratti is a natural parasite of the rat, and a useful and amenable laboratory model. Previous EST and microarray analyses of the S. ratti life cycle have identified genes whose expression was specific, or biased, to the parasitic adult stage, suggesting that they may play a key role in parasitism in this species. Here we have further investigated the expression of these genes (by RT-PCR) throughout the S. ratti life-cycle. We produced recombinant proteins in vitro for a subset of these genes, which were used in Western blot analyses to investigate the distribution of the gene products among different stages of the S. ratti life cycle. We tested the efficacy of these recombinant proteins as anti-S. ratti vaccines. One of the proteins was detected in the excretory/secretory products of the parasitic stages.

Continuity in ovine Johne's disease vaccination practices despite a decline in clinical disease.

The Gudair® vaccine has been commercially available in Australia for almost two decades for the control of ovine Johne's disease, but concerns have been raised about potential discontinuation of vaccination by producers after a decline in the incidence of clinical disease. An online questionnaire was distributed to Australian sheep producers to identify the proportion of respondents discontinuing the Gudair vaccine and reasons for discontinuation. Results revealed that 88% of sheep producers surveyed have continued to vaccinate their sheep with Gudair, with continuation greater for predominantly Merino sheep flocks. Reasons for discontinuing vaccination stemmed from management, economic or health concerns. These results suggest that Gudair is still widely used by Australian sheep producers and concerns about large-scale discontinuation are unfounded. These findings have implications for ovine Johne's disease control programs in Australia.

Acute stroke imaging. Part I: Fundamentals.

Neuroimaging is essential to stroke diagnosis and management. To date, the non-contrast CT has served as our main diagnostic tool. Although brain parenchymal changes visible on CT do provide valuable prognostic information, they provide limited insight into the potential for tissue salvage in response to reperfusion therapy, such as thrombolysis. Newer advanced CT and MRI based imaging techniques have increased the detection sensitivity for hyperacute and chronic parenchymal changes, including ischemia and hemorrhage, permit visualization of blood vessels and cerebral blood flow. This review outlines the basic principles underlying acquisition and interpretation of these newer imaging modalities in the setting of acute stroke. The utility of advanced brain parenchymal and blood flow imaging in the context of acute stroke patient management is also discussed. Part II in this series is a discussion of how these techniques can be used to rationally select appropriate patients for thrombolysis based on pathophysiological data.

Acute stroke imaging. Part II: The ischemic penumbra.

In acute ischemic stroke, the volume of threatened but potentially salvageable tissue, i.e. the ischemic penumbra, is critical to the success of all acute therapeutic interventions, most notably thrombolysis. Despite the availability of both CT and MRI based techniques to detect and assess the penumbra, advanced imaging of this type remains under-utilized. Although the optimal selection criteria are still being refined and technical improvements are ongoing, rapid imaging of the penumbra appears to be the most promising approach to expanding the acute thrombolysis population, as well as tailoring treatment based on specific pathophysiological findings. This second article in a two-part series reviews current evidence for penumbral-based treatment selection and discusses the barriers to implementation of these advanced imaging techniques in acute stroke management protocols.

Ejaculatory pattern in female rats without androgen treatment.

Adult female rats receiving long-term estrogen treatment displayed the species-typical motor pattern of ejaculation during copulation. This hormone treatment produced pituitary hypertrophy and concomitant pressure damage to brain areas dorsal to the pituitary, but did not cause clitoral hypertrophy. The demonstration of the ejaculatory pattern in perinatally untreated female rats indicates that the potential for the expression of the ejaculatory or "orgasmic" pattern is not dependent on exogenous androgen at any stage of development and is more widely represented among female mammals than previously believed.

Effects of a siderophore receptor and porin proteins-based vaccination on fecal shedding of Escherichia coli O157:H7 in experimentally inoculated cattle.

The efficacy of a vaccine containing outer membrane siderophore receptor and porin (SRP) proteins for reducing fecal prevalence and shedding of Escherichia coli O157:H7 was evaluated in cattle inoculated with E. coli O157:H7. Thirty calves were randomly assigned to one of two groups, and on days 1 and 21 these calves were given subcutaneous injections of either a placebo (control) or the vaccine. Blood was collected weekly to monitor the serum anti-SRP antibody titers. Two weeks after the second vaccination, calves were orally inoculated with a mixture of five strains of nalidixic acid-resistant (NalR) E. coli O157:H7. Fecal samples and rectoanal mucosal swabs were collected daily for the first 5 days and then three times each week for the following 4 weeks to determine the presence and enumerate the fecal concentration of NalR E. coli O157:H7. At necropsy on day 35, gut contents and tissue swabs were collected to determine the presence and concentration of NalR E. coli O157:H7. Vaccinated cattle had significantly higher anti-SRP antibody titers than did control cattle, with a significant treatment x week interaction (P < 0.01). Vaccination of cattle with the SRP protein tended to decrease fecal concentration (1.9 versus 1.6 log CFU/g) of NalR E. coli O157:H7 (P = 0.10). The number of calves that were fecal culture positive for E. coli O157:H7 was lower (P = 0.05) in the vaccinated group than in the control group. The E. coli O157:H7 SRP vaccine tended to reduce fecal prevalence and concentration of E. coli O157:H7 in cattle orally inoculated with NalR E. coli 0157:H7 and may be a useful prehavest intervention strategy. Future research must be conducted on natural prevalence in feedlot operations to further evaluate the efficacy of this novel vaccine.

Sequential microarray to identify timing of molecular responses to Haemonchus contortus infection in sheep.

Anthelmintics are currently the most common method of worm control. The emergence of worms with multiple-drug resistance and issues of residues in the food chain make alternative parasite control measures a priority. To develop improved and sustainable methods for controlling Haemonchus contortus such as genetic selection of resistant sheep, a better understanding of the host-parasite relationship is required. A trial was undertaken using sheep surgically implanted with abomasal fistulas to enable sequential biopsy of the abomasal mucosa during trickle infection with two strains of H. contortus. These were ivermectin-resistant CAVR and ivermectin-sensitive McMaster. From a gross parasitology perspective, this approach enabled the effect of developing immunity to be observed on both the establishment and maturation of two CAVR doses within and between groups. Since the only difference in parasite treatment between the groups was the staggering of the two CAVR doses, microarray results from biopsies taken on the same day in different groups were combined and compared between different biopsy dates to observe differential gene transcription over time. Differential gene transcription was detected by comparing transcription in our array data between different biopsy dates using a low P value screen (P<0.01) and by compiling a list of 82 immunoparasitology-related genes and examining transcription in this list with a higher P value screen (P<0.05). Our microarray data were validated in silico by comparison with intelectin 2, trefoil factor 3, calcium activated chloride channel and mucin 5 from other gene transcription studies and with phenotypic data such as the response by gammadelta T cells and immunoglobulins to H. contortus. The first four genes are involved in non-specific responses to infection and mucosal healing. These were upregulated at the early time points and intelectin 2 remained prominent throughout the trial. As the trial progressed, immunoglobulin genes became strongly upregulated. These included IgCgamma IgG2a heavy chain constant region, IGHE immunoglobulin heavy constant epsilon and IGHM immunoglobulin heavy constant mu.

Identifying obstacles to reducing the use of antibiotics to control porcine proliferative enteropathy.

Proliferative enteropathy (PE) is an enteric disease of pigs that results in diarrhoea, reduced growth rate, reduced feed conversion efficiency and sometimes death. A survey of 13 pig veterinary practitioners in Australia was conducted to determine: (1) PE control strategies (antibiotics and vaccination), (2) how the efficacies of these strategies are evaluated and (3) how reliance on antibiotics could be reduced by increasing vaccine adoption. Antibiotics were routinely prescribed in the diets of weaner, grower and finisher pigs by 9/13, 10/13 and 8/13 veterinarians, respectively, if vaccination was not implemented. Water-soluble antibiotics were prescribed less frequently than in-feed antibiotics. Efficacy of control strategies was assessed most often through reduced clinical signs (diarrhoea, 'tail-ender' pigs, death) and reduced lesion incidence at abattoir postmortem inspection. Twelve practitioners had recommended PE vaccination to their clients in the previous 6 months. Barriers to continued vaccine implementation included perceived lack of efficacy for pigs housed in bedded systems, high cost relative to medication and difficulties in vaccinating pigs post-weaning.

Comparative assessment of faecal diagnostics for detection and predictive modelling of endemic Fasciola hepatica infection in sheep and cattle on Australian farms.

The diagnosis, monitoring and flukicide efficacy testing of fasciolosis on-farm is reliant on non-terminal methods. The coproantigen ELISA (cELISA) has been recommended for diagnosis of fasciolosis and associated flukicide efficacy testing as an alternative to fluke egg counts for monitoring parasitism. Recently experimental multi-age infections have suggested that the reliability of efficacy results can be improved by a second cELISA testing at 6 weeks post-treatment (wpt) in addition to the generally accepted 1 wpt. A field study was conducted to determine the suitability of faecal fluke egg counts (FFEC) and cELISA as diagnostic, drug efficacy testing and epidemiological tools on Australian sheep and cattle farms. Faecal samples from sheep and/or cattle on three endemic farms were taken at monthly intervals for 12 months and examined by both methods. Normal farm management was maintained during the study period and opportunistic efficacy testing, in line with each farm's normal flukicide management was undertaken. Additionally, the suitability of the Ollerenshaw Index as a predictive model for fasciolosis under Australian conditions was examined. While both diagnostics demonstrated their value in the farm environment, the current data demonstrate a distinct and significant increase in diagnostic sensitivity for epidemiological studies by using the two tests in parallel. The agreement between the two diagnostics was found to be higher in cattle, despite the poor sensitivity of FFEC in this species. Similar levels of agreement between the two tests were demonstrated at both sheep properties, regardless of the marked difference in the intensity of F. hepatica challenge. Linear regression models demonstrated the results of the two diagnostics utilized in parallel were explained substantially (R2 = 0.91) as were series data (R2 = 0.88) when the respective models were fitted. In contrast, the fitted models for FFEC (R2 = 0.54) and cELISA (R2 = 0.58) were poor explanations for test outcomes. The outcomes of these models support previous findings that suggest that the two diagnostic tests are best utilized together, particularly in parallel. The application of the Ollerenshaw Index to Australian conditions requires further investigation.

Comparative assessment of faecal diagnostics for detection and predictive modelling of endemic Fasciola hepatica infection in sheep and cattle on Australian farms.

The diagnosis, monitoring and flukicide efficacy testing of fasciolosis on-farm is reliant on non-terminal methods. The coproantigen ELISA (cELISA) has been recommended for diagnosis of fasciolosis and associated flukicide efficacy testing as an alternative to fluke egg counts for monitoring parasitism. Recently experimental multi-age infections have suggested that the reliability of efficacy results can be improved by a second cELISA testing at 6 weeks post-treatment (wpt) in addition to the generally accepted 1 wpt. A field study was conducted to determine the suitability of faecal fluke egg counts (FFEC) and cELISA as diagnostic, drug efficacy testing and epidemiological tools on Australian sheep and cattle farms. Faecal samples from sheep and/or cattle on three endemic farms were taken at monthly intervals for 12 months and examined by both methods. Normal farm management was maintained during the study period and opportunistic efficacy testing, in line with each farm's normal flukicide management was undertaken. Additionally, the suitability of the Ollerenshaw Index as a predictive model for fasciolosis under Australian conditions was examined. While both diagnostics demonstrated their value in the farm environment, the current data demonstrate a distinct and significant increase in diagnostic sensitivity for epidemiological studies by using the two tests in parallel. The agreement between the two diagnostics was found to be higher in cattle, despite the poor sensitivity of FFEC in this species. Similar levels of agreement between the two tests were demonstrated at both sheep properties, regardless of the marked difference in the intensity of F. hepatica challenge. Linear regression models demonstrated the results of the two diagnostics utilized in parallel were explained substantially (R2 = 0.91) as were series data (R2 = 0.88) when the respective models were fitted. In contrast, the fitted models for FFEC (R2 = 0.54) and cELISA (R2 = 0.58) were poor explanations for test outcomes. The outcomes of these models support previous findings that suggest that the two diagnostic tests are best utilized together, particularly in parallel. The application of the Ollerenshaw Index to Australian conditions requires further investigation.

Direct modulation of the secretory machinery underlies PKA-dependent synaptic facilitation in hippocampal neurons.

Activation of protein kinase A (PKA) is known to facilitate synaptic transmission. Using synapses established by hippocampal neurons in culture, we show that dialysis of PKA inhibitors in the presynaptic neuron blocks synaptic facilitation produced by the adenylyl cyclase activator forskolin, demonstrating a presynaptic locus of action. Using ruthenium red, a tool that is known to stimulate exocytosis independently of Ca2+ influx, but in a manner sensitive to tetanus toxin, we find that the secretory process is directly up-regulated under conditions where the number of functional terminals remains unchanged, as revealed by imaging of FM1-43, a vital indicator of synaptic vesicle endocytosis. Taken together with our ultrastructural analysis that suggests no enhancement of docking, our data indicate that PKA causes synaptic facilitation by directly elevating the probability of exocytosis of individual vesicles in response to an invariant Ca2+ signal.

The cHS4 chromatin insulator reduces gammaretroviral vector silencing by epigenetic modifications of integrated provirus.

The cHS4 chromatin insulator has been shown to improve the expression of integrating gene transfer vectors by reducing the impact of silencing chromosomal position effects. To better understand the underlying mechanisms of this protection, we investigated the influence of this element on the epigenetic modifications of a gammaretroviral reporter vector. In HT1080 cells, we found that a fourfold increase in the level of green fluorescent protein (GFP) reporter expression from the cHS4-insulated vector was correlated with a twofold increase in acetylation at lysines 9 and 14 of histone H3, but not with CpG methylation. In a mouse bone marrow transduction and transplantation model, we found that a 10-fold increase in the likelihood of GFP expression from the cHS4-insulated vector was correlated with an eightfold increase in histone H3 acetylation, as well as a fourfold decrease in CpG methylation. Histone hyperacetylation peaked at the cHS4 core, and in vivo diminished nearly threefold through the central portion of the vector. Taken together, these studies demonstrate that the cHS4 chromatin insulator reduces gammaretroviral vector silencing by modulating epigenetic modifications of integrated provirus, and identify a specific topological distribution of these modifications that may prove informative for future vector designs.

Haemonchus contortus: development of a two-step, differential-display PCR to detect differential gene expression in nematodes from immune and naïve sheep.

Haemonchus contortus is a blood-feeding nematode which parasitizes the abomasum of sheep and represents a serious constraint to sheep production. Anthelmintics are currently the most common method of worm control but the worldwide development of multiple-drug resistance and issues of residues in the food chain make alternatives to anthelmintics a priority. Biotechnology-driven solutions to parasitism include vaccines and silencing of genes regulating nematode development. To pursue gene targets that may be suitable for parasite control, a two stage differential-display PCR (dd-PCR) approach was developed to observe differential gene expression between Haemonchus from immune and control sheep. Twenty-four reproducible differentially-expressed bands were identified in 60 pairs of dd-PCR comparisons. The first of these cloned and sequenced corresponded to the H. contortus 60S ribosomal protein L35A. The remaining bands are being cloned and validated and may provide new targets for parasite control.

Genomic analyses of Haemonchus contortus infection in sheep: abomasal fistulation and two Haemonchus strains do not substantially confound host gene expression in microarrays.

To determine whether fistulation and differing strains of Haemonchus contortus complicate genome analysis of the host response to infection, two pilot experiments examined parasite development and gene expression in the abomasal mucosa of parasitised sheep. No significant differentially-expressed genes were detected in a comparison between ivermectin-susceptible McMaster and ivermectin-resistant CAVR strains of H. contortus. This demonstrated that the sheep response was not significantly altered by the ivermectin-resistance status of the parasite. However, sheep infected with McMaster strain had a significantly lower proportion of larvae and a higher mean FEC at post-mortem than sheep infected with CAVR, suggesting that McMaster larvae advance to patency faster than CAVR larvae. Abomasal fistulation resulted in significant upregulation of three genes and significant downregulation of two genes. Fistulated sheep had significantly lower FEC than the other groups but the proportion of larvae at post-mortem was not significantly different to other groups infected with the same strain (CAVR). Hence fistulation does not alter establishment of the CAVR isolate, but may slow its progression to patency. The observation that different H. contortus strains and abomasal fistulation induced minimal changes in mucosal gene expression validated the design of a subsequent experiment (manuscript in preparation) where sequential biopsies taken during infection were analysed by microarray to describe the molecular responses which inhibit larval establishment.

Hematocrit Measurement with R2* and Quantitative Susceptibility Mapping in Postmortem Brain.

BACKGROUND AND PURPOSE: Noninvasive venous oxygenation quantification with MR imaging will improve the neurophysiologic investigation and the understanding of the pathophysiology in neurologic diseases. Available MR imaging methods are limited by sensitivity to flow and often require assumptions of the hematocrit level. In situ postmortem imaging enables evaluation of methods in a fully deoxygenated environment without flow artifacts, allowing direct calculation of hematocrit. This study compares 2 venous oxygenation quantification methods in in situ postmortem subjects. MATERIALS AND METHODS: Transverse relaxation (R2*) mapping and quantitative susceptibility mapping were performed on a whole-body 4.7T MR imaging system. Intravenous measurements in major draining intracranial veins were compared between the 2 methods in 3 postmortem subjects. The quantitative susceptibility mapping technique was also applied in 10 healthy control subjects and compared with reference venous oxygenation values. RESULTS: In 2 early postmortem subjects, R2* mapping and quantitative susceptibility mapping measurements within intracranial veins had a significant and strong correlation (R2 = 0.805, P = .004 and R2 = 0.836, P = .02). Higher R2* and susceptibility values were consistently demonstrated within gravitationally dependent venous segments during the early postmortem period. Hematocrit ranged from 0.102 to 0.580 in postmortem subjects, with R2* and susceptibility as large as 291 seconds-1 and 1.75 ppm, respectively. CONCLUSIONS: Measurements of R2* and quantitative susceptibility mapping within large intracranial draining veins have a high correlation in early postmortem subjects. This study supports the use of quantitative susceptibility mapping for evaluation of in vivo venous oxygenation and postmortem hematocrit concentrations.

Tolerance to solid organ transplants through transfer of MHC class II genes.

Donor/recipient MHC class II matching permits survival of experimental allografts without permanent immunosuppression, but is not clinically applicable due to the extensive polymorphism of this locus. As an alternative, we have tested a gene therapy approach in a preclinical animal model to determine whether expression of allogeneic class II transgenes (Tg's) in recipient bone marrow cells would allow survival of subsequent Tg-matched renal allografts. Somatic matching between donor kidney class II and the recipient Tg's, in combination with a short treatment of cyclosporine A, prolonged graft survival with DR and promoted tolerance with DQ. Class II Tg expression in the lymphoid lineage and the graft itself were sequentially implicated in this tolerance induction. These results demonstrate the potential of MHC class II gene transfer to permit tolerance to solid organ allografts.