The dispersion-brightness relation for fast radio bursts from a wide-field survey.

Despite considerable efforts over the past decade, only 34 fast radio bursts-intense bursts of radio emission from beyond our Galaxy-have been reported1,2. Attempts to understand the population as a whole have been hindered by the highly heterogeneous nature of the searches, which have been conducted with telescopes of different sensitivities, at a range of radio frequencies, and in environments corrupted by different levels of radio-frequency interference from human activity. Searches have been further complicated by uncertain burst positions and brightnesses-a consequence of the transient nature of the sources and the poor angular resolution of the detecting instruments. The discovery of repeating bursts from one source3, and its subsequent localization4 to a dwarf galaxy at a distance of 3.7 billion light years, confirmed that the population of fast radio bursts is located at cosmological distances. However, the nature of the emission remains elusive. Here we report a well controlled, wide-field radio survey for these bursts. We found 20, none of which repeated during follow-up observations between 185-1,097 hours after the initial detections. The sample includes both the nearest and the most energetic bursts detected so far. The survey demonstrates that there is a relationship between burst dispersion and brightness and that the high-fluence bursts are the nearby analogues of the more distant events found in higher-sensitivity, narrower-field surveys5.

Analysis of pressure-driven membrane preconcentration for point-of-care assays.

Point-of-care diagnostic devices for both physicians and patients themselves are now ubiquitous, but often not sensitive enough for highly dilute analytes (e.g., pre-symptomatic viral detection). Two primary methods to address this challenge include (1) increasing the sensitivity of molecular recognition elements with greater binding affinity to the analyte or (2) increasing the concentration of the analyte being detected in the sample itself (preconcentration). The latter approach, preconcentration, is arguably more attractive if it can be made universally applicable to a wide range of analytes. In this study, pressure-driven membrane preconcentration devices were developed, and their performance was analyzed for detecting target analytes in biofluids in the form of point-of-care lateral-flow assays (LFAs). The demonstrated prototypes utilize negative or positive pressure gradients to move both water and small interferents (salt, pH) through a membrane filter, thereby concentrating the analyte of interest in the remaining sample fluid. Preconcentration up to 33× is demonstrated for influenza A nucleoprotein with a 5 kDa pore polyethersulfone membrane filter. LFA results are obtained within as short as several minutes and device operation is simple (very few user steps), suggesting that membrane preconcentration can be preferable to more complex and slow conventional preconcentration techniques used in laboratory practice.

Open nanofluidic films with rapid transport and no analyte exchange for ultra-low sample volumes.

Moving to ultra-low (<100 nL) sample volumes presents numerous challenges, many of which can be resolved by implementation of open nanofluidic films. These nanofluidic films are fabricated using a hexagonal network of gold-coated open microchannels which capture all of the following innovative advantages: (1) sample volumes of <100 nL cm-2; (2) zero analyte exchange and loss with the film materials; (3) rapid and omni-directional wicking transport of >500 nL min-1 per square of film; (4) ultra-simple roll-to-roll fabrication; (5) stable and bio-compatible super-hydrophilicity for weeks in air by peptide surface modification. Validation includes both detailed in vitro characterization and in vivo validation with sweat transport from the human skin. Sampling times (skin-to-sensor) of <3 min were achieved, setting new benchmarks for the field of wearable sweat sensing. This work addresses significant challenges for sweat biosensing, or for any other nano-liter regime (<100 nL) fluid sampling and sensing application.

Complete validation of a continuous and blood-correlated sweat biosensing device with integrated sweat stimulation.

A wearable sweat biosensing device is demonstrated that stimulates sweat and continuously measures sweat ethanol concentrations at 25 s intervals, which is then correlated with blood ethanol during a >3 hour testing phase. The testing involves a baseline condition (no ethanol) followed by a rapid blood and sweat rise of ethanol (oral bolus), and finally, the physiological response of the body as ethanol concentrations return to baseline (metabolized). Data sets include multiple in vivo validation trials and careful in vitro characterization of the electrochemical enzymatic ethanol sensor against likely interferents. Furthermore, the data is analyzed through known pharmacokinetic models with a strong linear Pearson correlation of 0.9474-0.9996. The continuous nature of the data also allows analysis of blood-to-sweat lag times that range between 2.3 to 11.41 min for ethanol signal onset and 19.32 to 34.44 min for the overall pharmacokinetic curve lag time. This work represents a significant advance that builds upon a continuum of previous work. However, unresolved questions include operation for 24 hours or greater and with analytes beyond those commonly explored for sweat (electrolytes and metabolites). Regardless, this work validates that sweat biosensing can provide continuous and blood-correlated data in an integrated wearable device.

Cytotoxic T lymphocyte response to hepatitis C virus-derived peptides containing the HLA A2.1 binding motif.

The HLA class I-restricted cytotoxic T lymphocyte (CTL) response is a major defense mechanism in viral infections. It has been suggested that the CTL response may contribute to viral clearance and liver cell injury during hepatitis C virus (HCV) infection. To test this hypothesis requires an understanding of the characteristics of HCV-specific cytotoxic effector cells and identification of the target antigens to which they respond. To begin this process we stimulated peripheral blood mononuclear cells (PBMC) from a group of HLA-A2 positive patients with chronic hepatitis C with a panel of 130 HCV-derived peptides containing the HLA-A2 binding motif. Effector cells were tested for their capacity to lyse HLA-A2-matched target cells that were either sensitized with peptide or infected with a vaccinia virus construct containing HCV sequences. Using this approach we have identified nine immunogenic peptides in HCV, three of which are derived from the putative core protein, three from the nonstructural (NS) 3 domain, two from NS4 and one from NS5. Selected responses were shown to be HLA-A2 restricted, mediated by CD8+ T cells and to recognize endogenously synthesized viral antigen. Unexpectedly, peptide-specific CTL responses could also be induced in sero-negative individuals, suggesting in vitro activation of naive CTL precursors. The precursor frequency of peptide-specific CTL was 10 to 100-fold higher in infected patients compared to uninfected controls, and the responses were greatly diminished by removal of CD45 RO+ (memory) T cells. Further quantitative studies are clearly required to establish whether a correlation exists between the HCV-specific CTL response and the clinical course of this disease. Definition of the molecular targets of the human CTL response to HCV creates this opportunity, and may also contribute to the development of a T cell-based HCV vaccine.

Evaluating glioma therapies: modeling treatments and predicting outcomes.

BACKGROUND: Intra-arterial chemotherapy with carmustine (BCNU) and interstitial radiation therapy with the use of stereotactically placed 125I sources are aggressive local therapies for malignant glioma. These therapies emerged in the 1980s and both appeared promising in phase II studies but yielded disappointing results in subsequent randomized controlled trials by the Brain Tumor Cooperative Group (BTCG). Florell and colleagues had prepared us for the possibility that brachytherapy would have less impact on survival than anticipated from the phase II experience by demonstrating that patients who were judged eligible for interstitial radiation, but treated conventionally, lived significantly longer than those who were ineligible and had better than average outcomes. PURPOSE: To further examine the impact of patient selection on outcome, we used the database of Florell et al. to assess the survival of patients with malignant glioma who were eligible or ineligible for chemotherapy by three intra-arterial methods, one of which was similar to that employed by the BTCG in its randomized, controlled trial evaluating intra-arterial BCNU. METHODS: The medical records and computed tomography (CT) scans of 102 consecutive patients with malignant glioma receiving standard treatment (i.e., maximum feasible surgical resection, external-beam radiotherapy, and often adjuvant systemic chemotherapy) at a single cancer center in Canada during the calendar years 1988 and 1989 were used for this analysis. Based on CT imaging and blind to outcome, an interventional neuroradiologist decided which patients were eligible or ineligible for intra-arterial chemotherapy via injection of two major arteries, via injection of one major artery, or via selective middle-cerebral artery injection. A Karnofsky performance score of greater than or equal to 60 was required. The percent of eligible patients, the median survival time, and the distribution of prognostic factors were analyzed for each group of eligible and ineligible patients. Median survival times were compared with the use of the generalized Wilcoxon (Breslow) test. All P values were based on two-tailed tests. RESULTS: For two-vessel treatment, 72.5% of the patients (74 of 102) were eligible; the eligible patients on average lived longer than the ineligible patients (14.8 versus 3.5 months; P < .00001). For one-vessel treatment, 48% of the patients (49 of 102) were eligible; again, the eligible patients lived longer than the ineligible patients (18.4 versus 5.1 months; P < .00001). For middle-cerebral artery treatment, 30% of the patients (31 of 102) were eligible, and these eligible patients did live somewhat longer than the ineligible patients, but this result did not reach statistical significance (13.6 versus 9.9 months; P = .1304). Trends were similar for patients with glioblastoma multiforme and anaplastic glioma. The median duration of survival was 11.4 months for all patients. CONCLUSIONS: Patients who were eligible for intra-arterial chemotherapy lived significantly longer or somewhat longer (depending on the selection criteria used) than patients who were ineligible and had better than expected outcomes. Patients who were judged eligible for intra-arterial chemotherapy by the two-vessel method and the control group in the BTCG phase III trial of intra-arterial chemotherapy had similar median survival times (14.8 versus 14.0 months). IMPLICATIONS: Modeling treatments with the use of a comprehensive clinical and imaging database of unselected, conventionally treated patients may help investigators decide if new therapies warrant definitive evaluation in randomized trials by measuring the degree to which patient selection may have enhanced phase II study outcomes.

Preradiation intracarotid cisplatin treatment of newly diagnosed anaplastic gliomas. The CNS Cancer Consortium.

PURPOSE: This phase II study was performed to assess the response of patients with newly diagnosed, untreated malignant gliomas (anaplastic astrocytoma [AA] and glioblastoma multiforme [GBM]) to intracarotid (IC) cisplatin. PATIENTS AND METHODS: Eligibility criteria included surgical intervention limited to biopsy only, measurable contrast-enhancing tumor, and unilateral tumor location within the vascular territory of one internal carotid artery. Patients were scheduled to receive four infusions of IC cisplatin (75 mg/m2 every 4 weeks) before beginning standard radiotherapy. Twenty-six patients were treated, and 22 were assessable for response. RESULTS: Ten patients (45%) showed a greater than 25% decrease in the enhancing tumor area before radiotherapy with stabilization or improvement of neurologic deficits, and three patients (14%) had a greater than 70% decrease in tumor area. The likelihood of response to IC cisplatin was not clearly linked to patient age, tumor histology, or pretreatment tumor size. Myelosuppression, nephrotoxicity, and ototoxicity were mild. Optic neuropathy occurred in one patient, seizures in two, and fatal postinfusion cerebral edema in one. CONCLUSION: This study design, which permits assessment of the drug sensitivity of the untreated glioma, has shown definite antitumor activity of IC cisplatin in newly diagnosed malignant glioma patients.

Randomized, controlled trial of diabetic patient education: improved knowledge without improved metabolic status.

We randomized 749 insulin-treated patients on the rolls of the Mount Sinai Medical Center Diabetes Clinic in a controlled trial of diabetic patient education; 345 agreed to participate, of whom 165 were assigned to the education group and 180 to the control group. Cognitive scores increased from 5.3 +/- 1.6 to 5.8 +/- 1.6 in the education group, but there was no change in the control group, whose score was 5.3 +/- 1.7 before and after the intervention (P = .0073). HbA1c fell from 6.8 +/- 2.1 to 6.1 +/- 2.0% in the education group and from 6.6 +/- 2.0 to 6.3 +/- 2.0% in the control group, an insignificant difference (P = .1995). The fasting blood glucose decreased from 223 +/- 94 to 179 +/- 73 mg/dl in the education group and from 199 +/- 81 to 185 +/- 76 mg/dl in the controls (P = .1983). Triglycerides, high- and low-density lipoprotein cholesterol, and insulin dosage also failed to show significant variation among groups. The foot-lesion score showed similar progression in the education and control groups. Neither diastolic nor systolic blood pressure showed significantly greater change in the education or the control group, with falls noted, particularly in diastolic pressures, in both patient groups. Differences between the groups were not significant for sick days, hospitalizations, emergency room visits, or outpatient visits. The sample sizes of the study and control populations were sufficiently large to detect a difference in means between the education and control groups in the HbA1c, the primary outcome variable, of greater than 1.0%, with alpha = .05 and a power of .95. Thus, our study suggests that patient education may not be an efficacious therapeutic intervention in most adults with insulin-treated diabetes mellitus.

Infection and diabetes: the case for glucose control.

This review summarizes data concerning the host resistance to infection in diabetes and the influence of an acute infection upon the endocrinologic-metabolite status of the diabetic patient. While it is well known that acute infections lead to difficulty in controlling blood sugar levels and the infection is the most frequently documented cause of ketoacidosis, controversy persists as to whether or not patients with diabetes mellitus are more susceptible to infection than age- and sex-matched nondiabetic control subjects. Our data obtained from the charts of 241 diabetic patients who were being followed as outpatients show a striking direct correlation between the overall prevalence of infection (p less than 0.001) and the mean plasma glucose levels (representing three or more fasting glucose determinations taken at times when no evidence of infection existed). There is a significant diminution in intracellular bactericidal activity of leukocytes with Staphylococcus aureus and Escherichia coli in subjects with poorly controlled diabetes in comparison with the control group. Serum opsonic activity for both Staph. Aureus and E. coli were significantly lower than in the control subjects. Taken together, the results from published reports as well as our data suggest to us that good control of blood sugar in diabetic patients is a desirable goal in the prevention of certain infections (Candida vaginitis, for example) and to ensure maintenance of normal host defense mechanisms that determine resistance and response to infection.

Intracranial angioplasty for treatment of vasospasm after subarachnoid hemorrhage: technique and modifications to improve branch access.

Angioplasty of the proximal portions of major cerebral arteries at the base of the brain has shown promise as a therapy for symptomatic vasospasm after subarachnoid hemorrhage. The blind-ended, single-lumen balloon-dilatation catheter most widely used to date lacks steerability, limiting its application to unbranched stems and single branches at bi- or trifurcation points. To extend the capabilities of cerebral angioplasty, we describe two modifications of the basic technique that have allowed increased selectivity and successful angioplasty of multiple branches, both proximal and distal, involved by vasospasm. Of four patients treated, three showed early improvement in their clinical condition, likely attributable to the angioplasty procedure. Our modifications to the basic angioplasty technique enhanced its success. Further refinement of this technique in the treatment of vasospasm will make it safer in treating this serious and widespread disorder.

n-Butyl 2-cyanoacrylate--substitute for IBCA in interventional neuroradiology: histopathologic and polymerization time studies.

Despite the development of new alternative embolic agents, the endovascular treatment of brain arteriovenous malformations continues to frequently require the use of cyanoacrylic glue, especially in situations where particulate or sclerosing agents are ineffective, such as when flow is very rapid or fistulous. Because isobutyl 2-cyanoacrylate (IBCA), the most commonly used embolic glue, is no longer available or manufactured, a real need exists for an alternative fast polymerizing agent. In vivo and in vitro studies were performed to compare IBCA with n-butyl 2-cyanoacrylate (NBCA, supplied as Histoacryl Blue), a tissue adhesive approved for surgical use in some countries. Polymerization times in static plasma were compared, and the effect of the addition of iophendylate oil or glacial acetic acid on polymerization was assessed. Polymerization times in vivo were compared after intraarterial injection into the internal carotid artery in pigs using a standardized technique. The histopathologic reactions to each glue in the embolized pig rete were assessed and compared over a period of 0-60 days after embolization. Our results show that while NBCA polymerization is demonstrably faster than IBCA in vitro, intraarterial injections of each glue show no significant difference in polymerization times. Like IBCA, NBCA polymerization can be predictably prolonged by the addition of oil or glacial acetic acid, though the effect is less for NBCA. Histopathologic reactions were similar, with acute vasculitis observed, becoming chronic and granulomatous after about 1 month. Both glues showed frequent foci of extravascular extrusion through the embolized rete and recanalization of previously occluded embolized vessels. We conclude that NBCA has clinical and biologic behaviors similar to IBCA, and therefore should be an acceptable alternative to IBCA for intravascular use.

MR imaging after surgery for vertebrobasilar aneurysm.

We examined the safety and utility of high-field MR in patients who had surgery for cerebral aneurysms of the vertebrobasilar system. Eighteen posterior (and three coincidental anterior) circulation aneurysms were treated. Twenty-one MR scans were obtained at a mean postoperative interval of 7.2 days. The mean size of the preoperative vertebrobasilar aneurysm was 2.2 cm; six were giant (greater than 2.5 cm) and eight were large (greater than 1.5, less than or equal to 2.5 cm). In 17 patients, Sugita nonmagnetic clips were used. In one other, a Drake tourniquet was used. No ill effects occurred from scanning with a high-field imaging unit at 1.5 T. The MR clip artifact was much less obtrusive than that on CT. In 11 cases, the aneurysm could be partially imaged postoperatively, mainly in very large aneurysms or in those treated by clipping the parent vessel. Of these, two revealed residual lumina on MR and nine looked completely thrombosed. Postoperative angiography showed that in four of the thrombosed-appearing aneurysms a residual lumen with a mean diameter of 1.0 cm had been missed. In the patient imaged after application of a Drake tourniquet, no artifact was seen, and a good assessment of progressive partial thrombosis was obtained. Evolution of the signal intensity of new aneurysm thrombus, in those minimally or not obscured by artifact, coincides with patterns previously described for hemoglobin in intracerebral hematomas. The earliest hyperintensity could be seen in either the periphery or the center of the new thrombus. All 15 patients examined with new postoperative deficits showed appropriate lesions, mainly small brainstem ischemic foci. Postoperative CT (performed in all but four of these patients) missed over 80% of these lesions, mainly owing to artifact from clip or bone. We conclude that MR is better than CT in the postoperative assessment of aneurysm patients, particularly in demonstrating small zones of ischemia. High-field MR scanning is safe if nonmagnetic surgical clips are used. MR is not accurate in assessing residual lumina.

Pituitary apoplexy associated with a triple bolus test. Case report.

The authors report a case of pituitary apoplexy resulting in bilateral internal carotid artery occlusion, with marked depression of consciousness and hemiplegia. After transsphenoidal tumor decompression, restoration of flow in both carotid arteries was documented angiographically and the patient made an excellent clinical recovery. The unique aspect of this case is that the pituitary apoplexy was apparently precipitated by neuroendocrine manipulation, performed as a preoperative test of pituitary function.

A C9 related channel forming protein in the cytoplasmic granules of human large granular lymphocytes.

Large granular lymphocytes (LGL) from human blood maintained in culture for 2 to 6 weeks with IL-2 were found positive in the K562 cell killing assay. The cytoplasmic granules of the LGL were isolated, lysed and the soluble proteins were passed over a Sepharose-anti-C9 column. The retained protein was eluted with NaCl and found to consist by SDS polyacrylamide gel electrophoresis of essentially one component with a molecular weight of approximately 70 000. The protein did not give a positive precipitation test with anti-human C9 by Ouchterlony analysis, but it reacted reproducibly with anti-human C9 by Western blot analysis. By ELISA the cross reaction with human C9 was less than 1%. The C9 related lymphocyte protein lacked C9 hemolytic activity, but it formed functional pores in liposomes in presence of Ca++. These results suggest that the cytoplasmic granules of human LGL that are capable of killing NK target cells contain C9 related protein which is involved in the cellular cytotoxicity reaction.

In vitro resistance study of rupintrivir, a novel inhibitor of human rhinovirus 3C protease.

Rupintrivir (formerly AG7088) is an irreversible inhibitor of the human rhinovirus (HRV) 3C protease that has been demonstrated to have in vitro activity against all HRVs tested, consistent with its interaction with a strictly conserved subset of amino acids in the 3C protease. The potential for resistance was studied following in vitro serial passage of HRV serotypes 14, 2, 39, and Hanks in the presence of increasing rupintrivir concentrations. HRV variants with reduced susceptibilities to rupintrivir (sevenfold for HRV 14) or with no significant reductions in susceptibility but genotypic changes (HRV 2, 39, and Hanks) were initially isolated following 14 to 40 cumulative days in culture (three to six passages). Sequence analysis of the 3C protease identified one to three substitutions in diverse patterns but with common features (T129T/A, T131T/A, and T143P/S in HRV 14; N165T in HRV 2; N130N/K and L136L/F in HRV 39; T130A in HRV Hanks). Notably, three of the four HRV variants contained a substitution at residue 130 (residue 129 in HRV 14). Continued selection in the presence of escalating concentrations of rupintrivir (40 to 72 days) resulted in the accumulation of additional mutations (A121A/V and Y139Y/H in HRV 14, E3E/G and A103A/V in HRV 2, S105T in HRV 39), with only minimal further reductions in susceptibility (up to fivefold). The ability of specific substitutions to confer resistance was examined by susceptibility testing of HRV 14 variants constructed to contain 3C protease mutations. In summary, the slow accumulation of multiple amino acid substitutions with only minimal to moderate reductions in susceptibility highlight the advantages of 3C protease as an antiviral target.

Conservation of amino acids in human rhinovirus 3C protease correlates with broad-spectrum antiviral activity of rupintrivir, a novel human rhinovirus 3C protease inhibitor.

The picornavirus 3C protease is required for the majority of proteolytic cleavages that occur during the viral life cycle. Comparisons of published amino acid sequences from 6 human rhinoviruses (HRV) and 20 human enteroviruses (HEV) show considerable variability in the 3C protease-coding region but strict conservation of the catalytic triad residues. Rupintrivir (formerly AG7088) is an irreversible inhibitor of HRV 3C protease with potent in vitro activity against all HRV serotypes (48 of 48), HEV strains (4 of 4), and untyped HRV field isolates (46 of 46) tested. To better understand the relationship between in vitro antiviral activity and 3C protease-rupintrivir binding interactions, we performed nucleotide sequence analyses on an additional 21 HRV serotypes and 11 HRV clinical isolates. Antiviral activity was also determined for 23 HRV clinical isolates and four additional HEV strains. Sequence comparison of 3C proteases (n = 58) show that 13 and 11 of the 14 amino acids that are involved in side chain interactions with rupintrivir are strictly conserved among HRV and HEV, respectively. These sequence analyses are consistent with the comparable in vitro antiviral potencies of rupintrivir against all HRV serotypes, HRV isolates, and HEV strains tested (50% effective concentration range, 3 to 183 nM; n = 125). In summary, the conservation of critical amino acid residues in 3C protease and the observation of potent, broad-spectrum antipicornavirus activity of rupintrivir highlight the advantages of 3C protease as an antiviral target.

Inhibition of cytolytic lymphocytes by homologous restriction factor. Lack of species restriction.

Homologous restriction factor (HRF) has been shown to inhibit complement-mediated lysis in a species-restrictive manner. Human HRF is able to block lysis by human complement but not by complement from other species. HRF has also been found in the membrane of lymphokine-activated killer (LAK) cells. When this HRF is inserted into sheep erythrocyte membranes, it is able to protect the erythrocyte from LAK cell lysis. In this report, we show that while HRF can inhibit human complement but not rat complement-mediated hemolysis, it is able to inhibit LAK cell lysis by both human and rat LAK cells. HRF is therefore a more general protective protein than has been previously thought.

Self-protection of cytotoxic lymphocytes: a soluble form of homologous restriction factor in cytoplasmic granules.

A soluble form of homologous restriction factor (HRF) has been isolated from the cytoplasmic granules of human large granular lymphocytes that were cultured in the presence of recombinant interleukin 2 for 2-3 weeks. The granule-derived protein (approximately 65 kDa) is soluble in detergent-free solution and reacts with antibody produced to membrane HRF. HRF was first described as a 65-kDa membrane protein of human erythrocytes capable of inhibiting the formation of transmembrane channels by the membrane attack complex of complement. It has also been isolated from activated human lymphocytes and shown to confer upon these cells relative resistance to lysis by the membrane attack complex and by the complement component C9-related protein of human cytotoxic lymphocytes. The soluble HRF of lymphocyte granules inhibits reactive lysis of erythrocytes by the membrane attack complex of human complement. It was also found to be a potent inhibitor of (i) the cytolytic activity of the C9-related protein of human cytotoxic lymphocytes, (ii) human large granular lymphocyte cytotoxicity, and (iii) the cytotoxic activity of human CD8+ lymphocytes obtained by cell sorting from recombinant interleukin 2-activated peripheral blood mononuclear cells. It is proposed that granule-derived soluble HRF and cell surface-membrane-bound HRF are involved in the mechanism of self-protection of killer lymphocytes.

Mechanism of cytotoxicity of human large granular lymphocytes: relationship of the cytotoxic lymphocyte protein to the ninth component (C9) of human complement.

A Mr 70,000 protein was isolated from cytotoxic human large granular lymphocytes and shown to have cytotoxic activity. The protein was demonstrated to be immunochemically related to the ninth component (C9) of complement and was therefore designated C9-related protein (C9RP). This finding suggests that C9RP and C9 share homology in primary structure and have a common evolutionary ancestry. C9RP was isolated, by affinity chromatography employing anti-human C9-Sepharose, from either purified cytoplasmic granules or whole-cell lysates of cultured human large granular lymphocytes. The cells were isolated from healthy blood donors and maintained in interleukin-2-dependent cultures. The immunochemical crossreactivity of C9 with C9RP was 3-4%, using a murine anti-C9RP antiserum. Certain murine monoclonal antibodies to C9RP and to C9 inhibited killing of K562 cells by human large granular lymphocytes. Killed target cells, identified by propidium iodide staining and isolated by fluorescence-activated cell-sorting, exhibited clusters of circular membrane lesions that resembled poly(C9) in appearance. Polymerization of isolated C9RP in the presence of Ca2+ resulted in the formation of two different circular structures, one having an inner diameter of approximately equal to 60 A, and the other, of 125 A. Polymerized C9RP could be incorporated into liposomes and, as such, gave rise to channels of two different sizes. The smaller channel had a functional diameter of 50-90 A, and the bigger channel, a diameter greater than 102 A.