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To achieve secure quantum key distribution, all imperfections in the source unit must be incorporated in a security proof and measured in the lab. Here we perform a proof-of-principle demonstration of the experimental techniques for characterising the source phase and intensity fluctuation in commercial quantum key distribution systems. When we apply the measured phase fluctuation intervals to the security proof that takes into account fluctuations in the state preparation, it predicts a key distribution distance of over 100 km of fiber. The measured intensity fluctuation intervals are however so large that the proof predicts zero key, indicating a source improvement may be needed. Our characterisation methods pave the way for a future certification standard., Comment: 14 pages, 12 figures

There is a large gap between theory and practice in quantum key distribution (QKD) because real devices do not satisfy the assumptions required by the security proofs. Here, we close this gap by introducing a simple and practical measurement-device-independent-QKD type of protocol, based on the transmission of coherent light, for which we prove its security against any possible imperfection and/or side channel from the quantum communication part of the QKD devices. Our approach only requires to experimentally characterize an upper bound of one single parameter for each of the pulses sent, which describes the quality of the source. Moreover, unlike device-independent (DI) QKD, it can accommodate information leakage from the users' laboratories, which is essential to guarantee the security of QKD implementations. In this sense, its security goes beyond that provided by DI QKD, yet it delivers a secret key rate that is various orders of magnitude greater than that of DI QKD.

The core of security proofs of quantum key distribution (QKD) is the estimation of a parameter that determines the amount of privacy amplification that the users need to apply in order to distill a secret key. To estimate this parameter using the observed data, one needs to apply concentration inequalities, such as random sampling theory or Azuma's inequality. The latter can be straightforwardly employed in a wider class of QKD protocols, including those that do not rely on mutually unbiased encoding bases, such as the loss-tolerant (LT) protocol. However, when applied to real-life finite-length QKD experiments, Azuma's inequality typically results in substantially lower secret-key rates. Here, we propose an alternative security analysis of the LT protocol against general attacks, for both its prepare-and-measure and measure-device-independent versions, that is based on random sampling theory. Consequently, our security proof provides considerably higher secret-key rates than the previous finite-key analysis based on Azuma's inequality. This work opens up the possibility of using random sampling theory to provide alternative security proofs for other QKD protocols., 24 pages, 5 figures. v2: Corrected a technical issue; bold math was not displayed properly in Appendix B

Measurement-device-independent quantum key distribution (MDI-QKD) can remove all detection side-channels from quantum communication systems. The security proofs require, however, that certain assumptions on the sources are satisfied. This includes, for instance, the requirement that there is no information leakage from the transmitters of the senders, which unfortunately is very difficult to guarantee in practice. In this paper we relax this unrealistic assumption by presenting a general formalism to prove the security of MDI-QKD with leaky sources. With this formalism, we analyze the finite-key security of two prominent MDI-QKD schemes - a symmetric three-intensity decoy-state MDI-QKD protocol and a four-intensity decoy-state MDI-QKD protocol - and determine their robustness against information leakage from both the intensity modulator and the phase modulator of the transmitters. Our work shows that MDI-QKD is feasible within a reasonable time frame of signal transmission given that the sources are sufficiently isolated. Thus, it provides an essential reference for experimentalists to ensure the security of experimental implementations of MDI-QKD in the presence of information leakage., Comment: 46 pages, 11 figures. arXiv admin note: text overlap with arXiv:1803.09508

To guarantee the security of quantum key distribution (QKD), several assumptions on light sources must be satisfied. For example, each random bit information is precisely encoded on an optical pulse and the photon-number probability distribution of the pulse is exactly known. Unfortunately, however, it is hard to check if all the assumptions are really met in practice, and it is preferable that we have minimal number of device assumptions. In this paper, we adopt the differential-phase-shift (DPS) QKD protocol and drastically mitigate the requirements on light sources. Specifically, we only assume the independence among emitted pulses, the independence of the vacuum emission probability from a chosen bit, and upper bounds on the tail distribution function of the total photon number in a single block of pulses for single, two and three photons. Remarkably, no other detailed characterizations, such as the amount of phase modulation, are required. Our security proof significantly relaxes demands for light sources, which paves a route to guarantee implementation security with simple verification of the devices., 10 pages, 2 figures

In theory, quantum key distribution (QKD) offers information-theoretic security. In practice, however, it does not due to the discrepancies between the assumptions used in the security proofs and the behaviour of the real apparatuses. Recent years have witnessed a tremendous effort to fill the gap, but the treatment of correlations among pulses has remained a major elusive problem. Here, we close this gap by introducing a simple yet general method to prove the security of QKD with arbitrarily long-range pulse correlations. Our method is compatible with those security proofs that accommodate all the other typical device imperfections, thus paving the way towards achieving implementation security in QKD with arbitrary flawed devices. Moreover, we introduce a new framework for security proofs, which we call the reference technique. This framework includes existing security proofs as special cases and it can be widely applied to a number of QKD protocols.

Despite the enormous theoretical and experimental progress made so far in quantum key distribution (QKD), the security of most existing QKD implementations is not rigorously established yet. A critical obstacle is that almost all existing security proofs make ideal assumptions on the QKD devices. Problematically, such assumptions are hard to satisfy in the experiments, and therefore it is not obvious how to apply such security proofs to practical QKD systems. Fortunately, any imperfections and security-loopholes in the measurement devices can be perfectly closed by measurement-device-independent QKD (MDI-QKD), and thus we only need to consider how to secure the source devices. Among imperfections in the source devices, correlations between the sending pulses are one of the principal problems. In this paper, we consider a setting-choice-independent correlation (SCIC) framework in which the sending pulses can present arbitrary correlations but they are independent of the previous setting choices such as the bit, the basis and the intensity settings. Within the framework of SCIC, we consider the dominant fluctuations of the sending states, such as the relative phases and the intensities, and provide a self-contained information theoretic security proof for the loss-tolerant QKD protocol in the finite-key regime. We demonstrate the feasibility of secure quantum communication within a reasonable number of pulses sent, and thus we are convinced that our work constitutes a crucial step toward guaranteeing implementation security of QKD., Comment: 27 pages, 5 figures

In theory, quantum key distribution (QKD) allows secure communications between two parties based on physical laws. However, most of the security proofs of QKD today make unrealistic assumptions and neglect many relevant device imperfections. As a result, they cannot guarantee the security of the practical implementations. Recently, the loss-tolerant protocol (K. Tamaki et al., Phys. Rev. A, 90, 052314, 2014) was proposed to make QKD robust against state preparation flaws. This protocol relies on the emission of qubit systems, which, unfortunately, is difficult to achieve in practice. In this work, we remove such qubit assumption and generalise the loss-tolerant protocol to accommodate multiple optical modes in the emitted signals. These multiple optical modes could arise, e.g., from Trojan horse attacks and/or device imperfections. Our security proof determines some dominant device parameter regimes needed for achieving secure communication and, therefore, it can serve as a guideline to characterise QKD transmitters. Furthermore, we compare our approach with that of H.-K. Lo et al. (Quantum Inf. Comput., 7, 431–458, 2007) and identify which method provides the highest secret key generation rate as a function of the device imperfections. Our work constitutes an important step towards the best practical and secure implementation for QKD. Ministerio español de Economía y Competitividad | Ref. TEC2014-54898-R Ministerio español de Economía y Competitividad | Ref. TEC2017-88243-R Government of Japan | Ref. JP18H05237 18H05237 Government of Japan | Ref. JST-CREST JPMJCR 1671

An all-optical network is identified as a promising infrastructure for fast and energy-efficient communication. Recently, it has been shown that its quantum version based on ‘all-photonic quantum repeaters’—inheriting, at least, the same advantages—expands its possibility to the quantum realm, that is, a global quantum internet with applications far beyond the conventional Internet. Here we report a proof-of-principle experiment for a key component for the all-photonic repeaters—called all-photonic time-reversed adaptive (TRA) Bell measurement, with a proposal for the implementation. In particular, our TRA measurement—based only on optical devices without any quantum memories and any quantum error correction—passively but selectively performs the Bell measurement only on single photons that have successfully survived their lossy travel over optical channels. In fact, our experiment shows that only the survived single-photon state is faithfully teleported without the disturbance from the other lost photons, as the theory predicts., Storage-free quantum repeaters represent a viable alternative to quantum-memory-based ones. Here, the authors propose a modified scheme for Bell state measurements which reduces the necessary resources for realising such an all-photonic repeater, and show a proof-of-principle implementation.

In recent years, there has been a great effort to prove the security of quantum key distribution (QKD) with a minimum number of assumptions. Besides its intrinsic theoretical interest, this would allow for larger tolerance against device imperfections in the actual implementations. However, even in this device-independent scenario, one assumption seems unavoidable, that is, the presence of a protected space devoid of any unwanted information leakage in which the legitimate parties can privately generate, process and store their classical data. In this paper we relax this unrealistic and hardly feasible assumption and introduce a general formalism to tackle the information leakage problem in most of existing QKD systems. More specifically, we prove the security of optical QKD systems using phase and intensity modulators in their transmitters, which leak the setting information in an arbitrary manner. We apply our security proof to cases of practical interest and show key rates similar to those obtained in a perfectly shielded environment. Our work constitutes a fundamental step forward in guaranteeing implementation security of quantum communication systems., 37 pages, 5 figures

Most quantum communication tasks need to rely on the transmission of quantum signals over long distances. Unfortunately, transmission of such signals is most often limited by losses in the channel, the same issue that affects classical communication. Simple signal amplification provides an elegant solution for the classical world, but this is not possible in the quantum world, as the no-cloning theorem forbids such an operation and, thus, an alternative approach, a quantum repeater, is needed. Quantum repeaters enable one to create a known maximally entangled state between the end points of the network by first segmenting the network into pieces, creating entanglement between the segments, and then, connecting those entanglement to create the required long range entanglement. Quantum teleportation then allows an unknown quantum message to be transmitted between them using the long-range entangled state. This form of quantum communication will be at the heart of the future quantum Internet. In this review, we will detail various approaches to quantum repeaters, and discuss their expected performance and limitations.

Quantum key distribution (QKD) can achieve information-theoretic security, which is a provable security against any eavesdropping, given that all the devices the sender and the receiver employ operate exactly as the theory of security requires. Unfortunately, however, it is difficult for practical devices to meet all such requirements, and therefore more works have to be done toward guaranteeing information-theoretic security in practice, i.e., implementation security. In this paper, we review our recent efforts to enhance implementation security. We also have a brief look at a flaw in security proofs and present how to fix it.

Secure communication plays a crucial role in the Internet Age. Quantum mechanics may revolutionise cryptography as we know it today. In this Review Article, we introduce the motivation and the current state of the art of research in quantum cryptography. In particular, we discuss the present security model together with its assumptions, strengths and weaknesses. After a brief introduction to recent experimental progress and challenges, we survey the latest developments in quantum hacking and counter-measures against it., Comment: 13 pages, 5 figures

This paper reports experimental results for a long-term field trial of 1-GHz clock differential phase shift quantum key distribution that was incorporated in the test-bed optical fiber network installed in the Tokyo metropolitan area. A photon transmitter and a photon receiver were connected to a 90-km loop-back optical link with a 30-dB loss. Superconducting single photon detectors were employed to detect photons with a low dark count rate. Stable maintenance-free operation was achieved for 25 days, where the average sifted key generation rate and the quantum bit error rate were 11 kb/s and 2.6%, respectively. The average generation rate of a secure key after error correction and privacy amplification was 1.1 kb/s with a fluctuation of ± 0.5 kb/s. The achieved performance was examined using detailed bit error analysis. A comparison with meteorological data revealed the way in which the field environment influenced the key distribution performance.

It has long been known that quantum networks will enable a whole new range of communication tasks to be undertaken. The simplest is quantum key distribution (QKD) and are commercially available but currently only operate securely over distances around 100 km. A significant advance has been the development of mdiQKD, a scheme where Alice and Bob send one photon at a time to an intermediate node where a Bell measurement is performed. This Bell measurement can only succeed when both Alice and Bob photons arrive at the same time and so the key rate is limited by the exponential losses in both fibres. It limits the practical distance keys can be generated to less than 400km. Spatial or temporal multiplexing is a natural solution to this where one stores the photons that independently arrive from Alice and Bob. Only when the immediate node has both does it perform the Bell measurement. This means we are effectively only limited by fibres losses in one half of the channel. It however means one requires quantum memories at this immediate node, a technically challenging feat and one that changes the general resources used in QKD schemes. In our spatial multiplexed approach, we propose the use of an “all photonic non-destructive measurement (QND)” to herald whether the photon has arrived successfully from either Alice or Bob. Optical switches can them be used to route these photons to the Bell measurement, meaning that we are only limited by the channel loss between either Alice and the immediate node or Bob and the intermediate node, but not both. Further this can achieved without the use of quantum memories at all. Only optical switches, single-photon sources, photon detectors, and passive feed-forward techniques are required. Our approach can be applied naturally to entanglement distribution and so has applications beyond QKD.

The security of electronic communications is a topic that has gained noteworthy public interest in recent years. As a result, there is an increasing public recognition of the existence and importance of mathematically based approaches to digital security. Many of these implement digital signatures to ensure that a malicious party has not tampered with the message in transit, that a legitimate receiver can validate the identity of the signer and that messages are transferable. The security of most digital signature schemes relies on the assumed computational difficulty of solving certain mathematical problems. However, reports in the media have shown that certain implementations of such signature schemes are vulnerable to algorithmic breakthroughs and emerging quantum processing technologies. Indeed, even without quantum processors, the possibility remains that classical algorithmic breakthroughs will render these schemes insecure. There is ongoing research into information-theoretically secure signature schemes, where the security is guaranteed against an attacker with arbitrary computational resources. One such approach is quantum digital signatures. Quantum signature schemes can be made information-theoretically secure based on the laws of quantum mechanics while comparable classical protocols require additional resources such as anonymous broadcast and/or a trusted authority. Previously, most early demonstrations of quantum digital signatures required dedicated single-purpose hardware and operated over restricted ranges in a laboratory environment. Here, for the first time, we present a demonstration of quantum digital signatures conducted over several kilometers of installed optical fiber. The system reported here operates at a higher signature generation rate than previous fiber systems.

Although quantum key distribution (QKD) is theoretically secure, there is a gap between the theory and practice. In fact, real-life QKD may not be secure because component devices in QKD systems may deviate from the theoretical models assumed in security proofs. To solve this problem, it is necessary to construct the security proof under realistic assumptions on the source and measurement unit. In this paper, we prove the security of a QKD protocol under practical assumptions on the source that accommodate fluctuation of the phase and intensity modulations. As long as our assumptions hold, it does not matter at all how the phase and intensity distribute or whether or not their distributions over different pulses are independently and identically distributed. Our work shows that practical sources can be safely employed in QKD experiments.

We prove the unconditional security of the six-state protocol with threshold detectors and one-way classical communication. Unlike the four-state protocol (BB84), it has been proven that the squash operator for the six-state does not exist, i.e., the statistics of the measurements cannot be obtained via measurement on qubits. We propose a technique to determine which photon number states are important, and we consider a fictitious measurement on a qubit, which is defined through the squash operator of BB84, for the better estimation of Eve's information. As a result, we prove that the bit error rate threshold for the six-state protocol (12.611%) remains almost the same as the one of the qubit-based six-state protocol (12.619%). This clearly demonstrates the robustness of the six-state protocol against the use of the practical devices., Comment: 4 pages, 2 figures

Recent field demonstrations of quantum key distribution (QKD) networks hold promise for unconditionally secure communication. However, owing to loss in optical fibres, the length of point-to-point links is limited to a hundred kilometers, restricting the QKD networks to intracity. A natural way to expand the QKD network in a secure manner is to connect it to another one in a different city with quantum repeaters. But, this solution is overengineered unless such a backbone connection is intercontinental. Here we present a QKD protocol that could supersede even quantum repeaters for connecting QKD networks in different cities below 800 km distant. Nonetheless, in contrast to quantum repeaters, this protocol uses only a single intermediate node with optical devices, requiring neither quantum memories nor quantum error correction. Our all-photonic ‘intercity' QKD protocol bridges large gaps between the conventional intracity QKD networks and the future intercontinental quantum repeaters, conceptually and technologically., Quantum key distribution (QKD) holds promise for unconditionally secure communication, but due to fibre losses distances are so far restricted to intracity. Here, the authors present an all optical QKD protocol that can connect distant cities without the need of quantum repeaters or quantum error correction.

Quantum key distribution (QKD) is a way to securely expand the secret key to be used in One-time pad, and it is attracting great interest from not only theorists but also experimentalists or engineers who are aiming for the actual implementations. In this paper, we review the theoretical aspect of QKD, especially we focus on its security proof, and we briefly mention the possible problems and future directions.

Quantum key distribution (QKD) offers an unconditionally secure means of communication based on the laws of quantum mechanics. Currently, a major challenge is to achieve a QKD system with a 40 dB channel loss, which is required if we are to realize global scale QKD networks using communication satellites. Here we report the first QKD experiment in which secure keys were distributed over 42 dB channel loss and 200 km of optical fibre. We employed the differential phase shift quantum key distribution (DPS-QKD) protocol implemented with a 10-GHz clock frequency, and superconducting single photon detectors (SSPD) based on NbN nanowire. The SSPD offers a very low dark count rate (a few Hz) and small timing jitter (60 ps full width at half maximum). These characteristics allowed us to construct a 10-GHz clock QKD system and thus distribute secure keys over channel loss of 42 dB. In addition, we achieved a 17 kbit/s secure key rate over 105 km of optical fibre, which is two orders of magnitude higher than the previous record, and a 12.1 bit/s secure key rate over 200 km of optical fibre, which is the longest terrestrial QKD yet demonstrated. The keys generated in our experiment are secure against both general collective attacks on individual photons and a specific collective attack on multi-photons, known as a sequential unambiguous state discrimination (USD) attack., 15 pages, 5 figures. Original version

We report a case of tubulointerstitial nephritis and uveitis (TINU syndrome) with full type Fanconi syndrome. A 32-year-old woman presented with fatigue, anorexia and weight loss. Laboratory findings showed anemia, polyclonal hypergammaglobulinemia and moderate renal dysfunction. Tubular function abnormalities were normoglycemic glucosuria, panaminoaciduria, phosphaturia and kaliuresis leading to hypokalemia. Renal tubular acidosis and hypouricemia were also evident. Serum antistreptolysin O titer was high. Ocular symptoms (bilateral anterior uveitis) emerged soon after admission. Renal biopsy showed diffuse tubulointerstitial infiltration by lymphocytes and plasma cells without granuloma. Treatment with systemic steroids was given and renal function, and ocular symptom returned to normal with 3 months. Although tubular abnormalities involving TINU syndrome has already been reported, the disease associated with full type Fanconi syndrome has rarely been seen, and systemic steroid may be beneficial in reducing the development of tubulointerstitial injury.

Since the invention of Bennett-Brassard 1984 (BB84) protocol, many quantum key distribution (QKD) protocols have been proposed and some protocols are operated even in field environments. One of the striking features of QKD is that QKD protocols are provably secure unlike cryptography based on computational complexity assumptions. It has been believed that, to guarantee the security of QKD, Alice and Bob have to monitor the statistics of the measurement outcomes which are used to determine the amount of the privacy amplification to generate a key. Recently a new type of QKD protocol, called round robin differential phase shift (RRDPS) protocol, was proposed, and remarkably this protocol can generate a key without monitoring any statistics of the measurement outcomes. Here we report an experimental realization of the RRDPS protocol. We used a setup in which Bob randomly chooses one from four interferometers with different pulse delays so that he could implement phase difference measurements for all possible combinations with five-pulse time-bin states. Using the setup, we successfully distributed keys over 30 km of fiber, making this the first QKD experiment that does not rely on signal disturbance monitoring., 8 pages, 4 figures

Quantum communication holds promise for unconditionally secure transmission of secret messages and faithful transfer of unknown quantum states. Photons appear to be the medium of choice for quantum communication. Owing to photon losses, robust quantum communication over long lossy channels requires quantum repeaters. It is widely believed that a necessary and highly demanding requirement for quantum repeaters is the existence of matter quantum memories at the repeater nodes. Here we show that such a requirement is, in fact, unnecessary by introducing the concept of all photonic quantum repeaters based on flying qubits. As an example of the realization of this concept, we present a protocol based on photonic cluster state machine guns and a loss-tolerant measurement equipped with local high-speed active feedforwards. We show that, with such an all photonic quantum repeater, the communication efficiency still scales polynomially with the channel distance. Our result paves a new route toward quantum repeaters with efficient single-photon sources rather than matter quantum memories., 16 pages, 7 figures

Recently, a new type of quantum key distribution, called the round-robin differential phase-shift (RRDPS) protocol [Nature 509, 475 (2014)], was proposed, where the security can be guaranteed without monitoring any statistics. In this Letter, we investigate source imperfections and side-channel attacks on the source of this protocol. We show that only three assumptions are needed for the security, and no detailed characterizations of the source or the side-channel attacks are needed. This high robustness is another striking advantage of the RRDPS protocol over other protocols., Comment: The new version can deal with sending pulses that are classically correlated with each other in an arbitrary manner

We show the information-theoretic security proof of the differential-phase-shift (DPS) quantum key distribution (QKD) protocol based on the complementarity approach [arXiv:0704.3661 (2007)]. Our security proof provides a slightly better key generation rate compared to the one derived in the previous security proof in [arXiv:1208.1995 (2012)] that is based on the Shor-Preskill approach [Phys. Rev. Lett. ${\bf 85}$, 441 (2000)]. This improvement is obtained because the complementarity approach can employ more detailed information on Alice's sending state in estimating the leaked information to an eavesdropper. Moreover, we remove the necessity of the numerical calculation that was needed in the previous analysis to estimate the leaked information. This leads to an advantage that our security proof enables us to evaluate the security of the DPS protocol with any block size. This paper highlights one of the fundamental differences between the Shor-Preskill and the complementarity approaches., 15 pages, 5 figures

The measurement-device-independent quantum key distribution (MDI QKD) was proposed to make BB84 completely free from any side-channel in detectors. Like in prepare & measure QKD, the use of other protocols in MDI setting would be advantageous in some practical situations. In this paper, we consider SARG04 protocol in MDI setting. The prepare & measure SARG04 is proven to be able to generate a key up to two-photon emission events. In MDI setting we show that the key generation is possible from the event with single or two-photon emission by a party and single-photon emission by the other party, but the two-photon emission event by both parties cannot contribute to the key generation. On the contrary to prepare & measure SARG04 protocol where the experimental setup is exactly the same as BB84, the measurement setup for SARG04 in MDI setting cannot be the same as that for BB84 since the measurement setup for BB84 in MDI setting induces too many bit errors. To overcome this problem, we propose two alternative experimental setups, and we simulate the resulting key rate. Our study highlights the requirements that MDI QKD poses on us regarding with the implementation of a variety of QKD protocols.

Quantum key distribution promises unconditionally secure communications. However, as practical devices tend to deviate from their specifications, the security of some practical systems is no longer valid. In particular, an adversary can exploit imperfect detectors to learn a large part of the secret key, even though the security proof claims otherwise. Recently, a practical approach---measurement-device-independent quantum key distribution---has been proposed to solve this problem. However, so far its security has only been fully proven under the assumption that the legitimate users of the system have unlimited resources. Here we fill this gap and provide a rigorous security proof against general attacks in the finite-key regime. This is obtained by applying large deviation theory, specifically the Chernoff bound, to perform parameter estimation. For the first time we demonstrate the feasibility of long-distance implementations of measurement-device-independent quantum key distribution within a reasonable time-frame of signal transmission., 21 pages, 4 figures

The measurement-device-independent quantum key distribution (MDI QKD) was proposed to make BB84 completely free from any side-channel in detectors. Like in prepare & measure QKD, the use of other protocols in MDI setting would be advantageous in some practical situations. In this paper, we consider SARG04 protocol in MDI setting. The prepare & measure SARG04 is proven to be able to generate a key up to two-photon emission events. In MDI setting we show that the key generation is possible from the event with single or two-photon emission by a party and single-photon emission by the other party, but the two-photon emission event by both parties cannot contribute to the key generation. On the contrary to prepare & measure SARG04 protocol where the experimental setup is exactly the same as BB84, the measurement setup for SARG04 in MDI setting cannot be the same as that for BB84 since the measurement setup for BB84 in MDI setting induces too many bit errors. To overcome this problem, we propose two alternative experimental setups, and we simulate the resulting key rate. Our study highlights the requirements that MDI QKD poses on us regarding with the implementation of a variety of QKD protocols., 15 pages, 10 figures

In this study, we propose a method for generating cluster states of atoms in an optical lattice. By utilizing the quantum properties of Wannier orbitals, we create an tunable Ising interaction between atoms without inducing the spin-exchange interactions. We investigate the cause of errors that occur during entanglement generations, and then we propose an error-management scheme, which allows us to create high-fidelity cluster states in a short time.

Transforming growth factor-β1 (TGF-β1) has an important role in the pathogenesis of glomerular damage by influencing matrix metabolism. An association of TGF-β1 with glomerulosclerosis and interstitial fibrosis has been shown in various renal diseases, suggesting that TGF-β1 may serve as a diagnostic marker of glomerular diseases. The aim of this study is to determine the usefulness of urinary TGF-β1 values to monitor therapeutic effects of steroids in patients with immunoglobulin A (IgA) nephropathy. Concentrations and activation rates of TGF-β1 (mature/total) were determined in urine of patients with renal diseases by means of a double-antibody enzyme immunoassay. The urinary TGF-β1 level before steroid therapy was compared with renal histological characteristics, creatinine clearance, and proteinuria in patients with a variety of renal diseases. Urinary excretion of total and mature TGF-β1 was significantly greater in patients with crescentic glomerulonephritis and IgA nephropathy than in healthy controls, whereas the activation rate of urinary TGF-β1 was similar among patients with other renal diseases. Urinary TGF-β1 excretion at the time of renal biopsy significantly correlated with the degree of crescent formation in patients with IgA nephropathy, but not in those with glomerular sclerosis or tubulointerstitial fibrosis. Urinary excretion of total and mature TGF-β1 was reduced in patients with IgA nephropathy after treatment with prednisolone (0.8 mg/kg/d) for 1 month. The activation rate of urinary TGF-β1 also decreased significantly after steroid therapy. Urinary TGF-β1 values therefore may be useful to assess disease activity or the effects of steroid therapy in patients with IgA nephropathy. © 2001 by the National Kidney Foundation, Inc.

SUMMARY: The effects of a high salt diet on renal destruction and the therapeutic effects of amiloride (Na+/H+ exchanger inhibitor) and furosemide (Na+K+/2Cl− exchanger inhibitor) were examined in 5/6-nephrectomized rats fed a high salt diet. A simultaneous analysis of the effects of a high salt intake on the renal expression of Na+/H+ exchanger-1 (NHE-1), transforming growth factor-β1 (TGF-β1) or platelet-derived growth factor-B (PDGF-B) mRNA was performed in this model. the 5/6-nephrectomized Sprague-Dawley rats were given a diet containing 8 or 1% sodium chloride for 5 weeks. This high salt diet accelerated the elevation of blood pressure and aggravated both glomerulosclerosis and interstitial fibrosis in 5/6-nephrectomized rats. the daily administration of amiloride was found to be protective against the elevation of blood pressure, glomerular hypertrophy and the aggravation of renal histology which were induced by a high salt diet. the expression of TGF-β1 and PDGF-B mRNA was up-regulated by a high salt diet, but the expression of NHE-1 mRNA was not. the overexpression of TGF-β1 and PDGF-B mRNA was reduced by the daily administration of amiloride but not by furosemide. In conclusion, the destructive effects of a high salt diet on the kidneys may be mediated through hypertension, glomerular hypertrophy and the overexpression of the growth factors. Amiloride may thus be more protective for high salt induced renal aggravation than furosemide, although the expression of NHE-1 mRNA did not show any substantial increase due to a high salt diet.