Search

It is thought that lymphovenous communications may allow lymph to enter blood before the thoracic duct (TD). Whether this occurs physiologically1 or in response to lymphatic dysfunction2,3 is unclear. These images of a 54-year-old man who initially presented with right-sided, painless, intermittent, pitting lower limb swelling support the existence of such communications. He was initially investigated with lymphoscintigraphy. Five years later, the swelling became bilateral and he underwent further lymphoscintigraphy. On both occasions, 20 MBq of Tc-99m-nanocolloid (General Electric, UK) was injected subcutaneously into the first web spaces of both feet, followed by gamma camera imaging immediately after injection (0 min) and at 45 and 150 minutes post injection. He undertook no strenuous exercise before completion of imaging. Anterior projections (Panels B and D) illustrate very heavy hepatic and splenic activity at 150 minutes in the first and second studies. There was no activity in the liver at 0 or 45 minutes in either study (anterior projections; Panels A and C), excluding intravascular

Peripheral oedema is commonly seen in the yellow nail syndrome (YNS). Contrast lymphangiography has shown abnormal collecting lymphatics in some patients with YNS. In this study, lymphatic function in the upper and lower limbs of 17 patients with YNS, in normal controls, and in patients with established classical lymphoedema, has been assessed using quantitative lymphoscintigraphy. Nine subjects with YNS had swelling of the legs and two had features typical of lymphoedema. The lymphatic drainage was significantly reduced in the legs of patients with YNS but not to the level seen in lymphoedema. Lymphatic function was also reduced in the arms in patients with YNS. Venous insufficiency did not contribute to the leg oedema. These results suggest that the underlying cause of YNS is not primarily a lymphatic abnormality. The lymphatic impairment associated with YNS appears to be secondary, and predominantly functional in nature, rather than due to structural changes.

Lipoedema is a common but infrequently recognized condition causing bilateral enlargement of the legs in women. Although generally considered to be the result of an abnormal deposition of subcutaneous fat with associated oedema, the precise mechanisms responsible for oedema formation have yet to be fully established. In order to evaluate the possible role of lymphatic or venous dysfunction in the pathogenesis of lipoedema, 10 patients were investigated by photoplethysmography (venous function) and quantitative lymphoscintigraphy (lymphatic function). The results were compared with those from patients with primary lymphoedema and those from healthy volunteers. The results demonstrated minor abnormalities of venous function in only two patients. One patient had moderately impaired lymphatic function in both legs and seven patients had a marginal degree of impairment in one or both legs. However, in none of these cases did the impairment attain the low levels seen in true lymphoedema. Lipoedema appears to be a distinct clinical entity best classified as a lipodystrophy rather than a direct consequence of any primary venous or lymphatic insufficiency.

BACKGROUND: Surgical management of lymphedema includes removal of affected tissues (excisional procedures), or operations that create new lymphatic connections (physiologic procedures). The purpose of this study was to determine if suction-assisted lipectomy (an excisional procedure) has physiologic effects and improves lymphatic function.

The goal of reconstructive lymphatic surgery is to restore normal lymphatic function to “cure” permanently the lymphedematous limb in patients with lymphedema. In reality, reconstructive surgery remains an adjunctive treatment at best, with its current indication being refractory lymphedema in patients treated with complex decongestive therapy (CDT) alone. The role of reconstructive lymphatic surgery remains controversial and is far from being accepted as standard independent therapy because of multiple reasons. However, reconstructive surgery appears to be most effective in controlling the progression of lymphedema during the early stages when the paralyzed lymph vessels are still able to function and recover. Our experience in reconstructive surgery has shown that improved long-term results are dependent on prolonged patient compliance with maintenance CDT and the prevention and treatment of infection. To better understand the role of reconstructive surgery in the management of chronic lymphedema, well-constructed clinical trials based on well-organized multicenter studies with similar protocols are mandated. For the future, it remains the only possible treatment method capable of providing a cure.

Lymphedema of the lower limbs is a well-known chronic condition. The cause of lymphedema can be either primary or secondary. Lymphoscintigraphy is a simple and reliable method for evaluation of lymphatic function. We illustrate the different lymph drainage patterns in 4 cases of lower limb edema, with either primary or secondary causes. In all cases, planar images were obtained after bipedal administration of 99mTc antimony sulfur colloid.

All dietary lipids are transported to venous circulation through the lymphatic system, yet the underlying mechanisms that regulate this process remain unclear. Understanding how the lymphatics functionally respond to changes in lipid load is important in the diagnosis and treatment of lipid and lymphatic related diseases such as obesity, hypercholesterolemia, and lymphedema. Therefore, we sought to develop an in situ imaging system to quantify and correlate lymphatic function as it relates to lipid transport. A custom-built optical set-up provides us with the capability of dual-channel imaging of both high-speed bright-field video and fluorescence simultaneously. This is achieved by dividing the light path into two optical bands. Utilizing high-speed and back-illuminated CCD cameras and post-acquisition image processing algorithms, we have the potential quantify correlations between vessel contraction, lymph flow and lipid concentration of mesenteric lymphatic vessels in situ. Local flow velocity is measured through lymphocyte tracking, vessel contraction through measurements of the vessel walls and lipid uptake through fluorescence intensity tracking of a fluorescent long chain fatty acid analogue, Bodipy FL C16. This system will prove to be an invaluable tool for both scientists studying lymphatic function in health and disease, and those investigating strategies for targeting the lymphatic system with orally delivered drugs.

Lymphedema is the accumulation of interstitial fluid within tissues due to the impairment of lymphatic function. Dysfunction can result from direct obstruction of lymphatic vessels, absence of lymphatic vessels, or inadequate lymphatic function. From congenital forms of lymphedema, such as Milroy disease, to acquired forms of lymphedema, such as filiarisis lymphedema or post-surgical lymphedema, lymphatic dysfunction contributes significantly to the world’s human disease burden.

Extensive attention has been directed to lymphedema involving the extremities. However, there has been relatively limited study of the cutaneous lymphatics of the head and neck. In this review of head and neck lymphatics, we capsulize the history of the lymphatics, the anatomy of the cutaneous lymphatics, lymphatic function and physiology, and imaging modalities used to define this intricate vascular system. To appreciate the clinical challenges associated with head and neck lymphatic dysfunction, we also provide an overview of disease processes of the cutaneous lymphatics and their treatment, theories on the etiology of lymphedema, and future directions to better understand lymphatic function and disease. Knowledge of the cutaneous lymphatics of the head and neck are critical to the clinical evaluation of patients, who present with this debilitating condition and to our understanding of its pathogenesis and appropriate management.

OBJECTIVE The objective of our study was to examine the frequency and significance of visualization of popliteal nodes during lymphoscintigraphy for the investigation of lower extremity swelling. MATERIALS AND METHODS Technetium-99m-labeled nanocolloid was injected subcutaneously in the first web spaces of both feet of 204 consecutive patients (69 males, 135 females; age range, 11-79 years) undergoing routine, clinically indicated lymphoscintigraphy; imaging was performed 5, 45, and 150 minutes after injection. The patients were asked not to undertake any vigorous exercise between the injection and completion of imaging. RESULTS No popliteal nodes were visualized in 29 patients in whom there was no evidence of lymphedema on clinical or lymphoscintigraphic examination (group 1). Unilateral or bilateral popliteal nodes were visualized in 10 of 39 patients (25.6%) with clinical evidence of lymphedema but normal lymphoscintigraphy findings (group 2) (p < 0.005 vs group 1). In 136 patients with clinical evidence of lymphedema and abnormal lymphoscintigraphy findings (group 3), unilateral or bilateral popliteal nodes were visualized in 59 (43.4%) (p < 0.0001 vs group 1). Popliteal nodes were visualized in 40 of 73 limbs with "dermal backflow" (54.8%) and 42 of 335 limbs without dermal backflow (12.5%) (p < 0.0001). CONCLUSION Popliteal node visualization after subcutaneous foot web space injection is an important sign of abnormal lymphatic function in patients with clinical lymphedema of the lower extremities.

There is a lack of available methods to noninvasively quantify lymphatic function in small experimental animals, a necessity for studies on lymphatic system pathophysiology. We present a new method to quantify lymph flow in mice and rats, based on optically monitoring the depot clearance of near-infrared fluorescently labeled albumin and subsequent calculation of removal rate constants ( k). BSA was conjugated with Alexa680 NHS ester and remained stable in protein-rich solutions without free dye dissociation. To assess lymph flow, mice or rats were imaged every 30 or 60 min during a 3- to 6-h period following an intradermal injection of 0.5 or 1 μl Alexa680-albumin. Mice were awake between measurements, whereas rats were anesthetized throughout the experiment. The k, a parameter defined as equivalent to lymph flow, was calculated from the slopes of the resultant log-linear washout curves and averaged −0.40 ± 0.03 and −0.30 ± 0.02%/min for control C57BL/6 and C3H mice, respectively. Local administration of the vasoconstrictor endothelin-1 in mice led to a significant reduction in k, whereas overhydration in rats increased k, reflecting the coupling between capillary filtration and lymph flow. Furthermore, k was 50% of wild type in lymphedema Chy mice where dermal lymphatics are absent. We conclude that lymph flow can be determined as its rate constant k by optical imaging of depot clearance of submicroliter amounts of Alexa680-albumin. The method offers a minimally invasive, reproducible, and simple alternative to assess lymphatic function in mice and rats.

OBJETIVO: Descrever o padrão linfocintilográfico do membro superior em mulheres no pré-operatório de câncer de mama. MÉTODOS: Foram estudadas 37 pacientes que realizaram a linfocintilografia até 30 dias antes da cirurgia, sendo 37 estudos linfocintilográficos de membros superiores ipsilaterais à cirurgia e 32 contralaterais. O protocolo de exame consistiu na realização de imagens estáticas do membro superior em semiflexão após 10 minutos, 1 e 2 horas da injeção subcutânea de 1 mCi (37 MBq) de dextran-99mTc no dorso da mão. Foram feitas análises da velocidade de aparecimento dos linfonodos axilares (I, visíveis aos 10 minutos; II, 1 hora; III, 2 horas e IV, não visíveis) e do grau (intensidade) de captação dos mesmos (a, acentuada; b, moderada; c , discreta e d, ausente). RESULTADOS: Quatro (11%) pacientes apresentaram o padrão de estado da funcionalidade linfática considerado ideal (Ia) no membro superior ipsilateral, enquanto seis (19%) apresentaram no contralateral. Três (8%) apresentaram a pior classificação (IVd) no membro superior ipsilateral e duas (6%) no contralateral. As demais pacientes apresentaram estados intermediários de velocidade e intensidade de captação. CONCLUSÃO: Este estudo encontrou relevantes alterações na linfocintilografia pré-operatória, demonstrando a preexistência de diferenças funcionais do sistema linfático. OBJECTIVE: To describe the preoperative upper limb lymphoscintigraphic pattern in women with breast cancer. METHODS: Thirty-seven patients undergoing lymphoscintigraphy within 30 days of surgery were investigated. Lymphoscintigraphic studies of 37 upper limbs ipsilateral to surgery and 32 contralateral upper limbs were performed. The examination protocol consisted in obtaining static images of the upper limb in semi-flexion after 10 minutes, and 1 and 2 hours after subcutaneous injection of 1 mCi (37 MBq) of Tc-99m-dextran in the dorsum of the hand. The velocity of axillary lymph node visualization (I, visible at 10 minutes; II, 1 hour; III, 2 hours; and IV, invisible) and degree (intensity) of nodal uptake (a, marked; b, moderate; c,mild; and d, absent) were analyzed. RESULTS: Optimal lymphatic functional pattern (Ia) was observed in four (11%) patients, in the ipsilateral upper limb, and six (19%), in the contralateral upper limb. Worse condition was observed in three (8%) patients (IVd) in the ipsilateral upper limb and two (6%) patients in the contralateral upper limb. The remaining patients showed intermediate states of velocity and uptake intensity. CONCLUSION: This study found relevant changes in preoperative lymphoscintigraphy, demonstrating preexisting functional differences in the lymphatic system.

Chronic lymphedema continues to be a challenge in both diagnosis and management. The diagnostic dilemma remains about how to best define detailed anatomy and lymphatic function, Whereas the problem with treatment remains our inability to cure chronic lymphedema. Still, both evaluation and treatment have greatly improved in recent years. Progress in genetics, imaging studies, physical therapy, and microsurgical techniques have sparked interest in chronic lymphedema, a disease long considered to be the stepchild of medicine. This textbook is testimony to the increasing interest in the investigation and treatment of lymphatic disorders.

While the lymphatic system is increasingly associated with diseases of prevalence, study of these diseases is difficult owing to the paucity of imaging techniques with the sensitivity and temporal resolution to discriminate lymphatic function. Herein, we review the known, pertinent features of the human lymphatic system in health and disease and set the context for a number of emerging studies that use near-infrared fluorescence imaging to non-invasively assess tumor draining lymphatic basins in cancer patients, intraoperatively guide resection of first draining lymph nodes, and to interrogate the difference between normal and aberrant lymphatic structure and function.

In this review, we provide a comprehensive summary of noninvasive imaging modalities used clinically for the diagnosis of lymphatic diseases, new imaging agents for assessing lymphatic architecture and cancer status of lymph nodes, and emerging near-infrared (NIR) fluorescent optical imaging technologies and agents for functional lymphatic imaging. Given the promise of NIR optical imaging, we provide example results of functional lymphatic imaging in mice, swine, and humans, showing the ability of this technology to quantify lymph velocity and frequencies of propulsion resulting from the contractility of lymphatic structures.

Background: Our objective was to develop an animal model of postsurgical lymphedema that would permit quantitation of edema and lymphatic function after the removal of a single popliteal lymph node in sheep. Methods: As a measure of lymph transport, 125I-human serum albumin was injected into prenodal vessels at 8, 12 and 16 weeks after nodal excision, and plasma levels of the protein tracer were used to calculate the transport rate of the tracer to blood (percent injected per hour). Edema was quantified from the circumferential measurement of the hind limbs. Results and Conclusions: Following nodal excision, the limbs became progressively more edematous up to 3 days after nodectomy. After this, the swelling decreased but had not resolved even at 16 weeks after surgery. Compared with control limbs (17.2 ± 0.6; n = 7), lymphatic function was depressed at 8 weeks after surgery (10.6 ± 1.5; n = 7). At 12 (14.4 ± 1.0; n = 7) and 16 weeks (13.9 ± 1.0; n = 6), regeneration of lymphatic vessels at the excision site helped to restore about 80% of lymphatic capacity. These techniques may be helpful in understanding the pathophysiology associated with cancer-related postsurgical lymphedema and may facilitate the development of new strategies to treat or prevent this condition.

Chronic physical activity results in adaptations in many aspects of human physiology, while specific training can directly influence structural changes. It remains unknown if habitual exercise influences upper extremity lymphatic function in females; thus, the purpose of this cross-sectional study was to compare different exercise stresses on lymphatic function in ten upper body trained females with ten untrained females.Participants underwent a maximal upper body aerobic test on an arm crank ergometer before undergoing three randomly assigned lymphatic stress tests. Lymphoscintigraphy was used to quantify lymphatic function. (99m)Tc-antimony colloid was injected into the third web space of each hand, followed by 1 min spot views taken with a gamma-radiation camera. The maximal stress test required individuals to repeat their initial maximal exercise test. The subjects were then imaged every 10 min until 60 min were reached. The submaximal stress test involved arm cranking for 2.5 min at 0.6 W x kg(-1), followed by 2.5 min of rest, repeated for 60 min. The final stress test was a 60 min seated resting session. The clearance rate (CR) and axillary uptake (AX) were determined. Only AX post maximal exercise was significantly different between trained and untrained, p=0.009. All other measures of lymphatic function between groups were similar.This study demonstrates no significant difference in lymphatic function between upper body trained and untrained females.

Publisher Summary This chapter attempts to provide an overview of the current understanding of the lymphatic microcirculation, focusing on the prenodal microlymphatics vessels. It is written from the context of the lymphatic transport system. While the understanding of lymphatic microcirculation lags significantly behind that of the blood microcirculation, the progression of lymphatic biology has entered a phase of renewed interest. Considering the importance of lymphatic muscle to function, that is, the lymphatic system requires phasic and tonic lymphatic contractions to generate and regulate lymph flow, understanding lymphatic muscle is crucial to our overall understanding of lymphatic biology. The precise point in the collecting lymphatic architecture at which muscle cells appear is dependent on the tissue and species. Lymphatic muscle is variably innervated in different tissues and species and neural activation can have different effects on lymphatic muscle contraction depending upon the nerve type. In order to better understand microlymphatic function, an integrated understanding of all of the cells present in the lymphatic vessels needs to be developed. It is hoped that this renewed interest will help further define the regulation of microlymphatic function, including the cellular/molecular mechanisms as well as an integration of these cellular/molecular mechanisms back into overall lymphatic function.

Substantial advances have accrued over the last decade in the identification of the processes that contribute to lymphatic vascular development in health and disease. Identification of distinct regulatory milestones, from a variety of genetic models, has led to a stepwise chronology of lymphatic development. Several molecular species have been identified as important tissue biomarkers of lymphatic development and function. At present, vascular endothelial growth-factor receptor (VEGFR)-3/VEGF-C/VEGF-D signaling has proven useful in the identification of clinical lymphatic metastatic potential and the assessment of cancer prognosis. Similar biomarkers, to be utilized as surrogates for the assessment of inherited and acquired diseases of the lymphatic circulation, are actively sought, and will represent a signal advance in biomedical investigation.

Because of the role that lymphatics have in fluid and macromolecular exchange, lymphatic function has been tightly tied to the study of the microcirculation for decades. Despite this, our understanding of many basic tenets of lymphatic function is far behind that of the blood vascular system. This is in part due to the difficulty inherent in working in small, thin-walled, clear lymphatic vessels and the relative lack of lymphatic specific molecular/cellular markers. The application of cellular and molecular tools to the field of lymphatic biology has recently produced some significant developments in lymphatic endothelial cell biology. These have propelled our understanding of lymphangiogenesis and related fields forward. Whereas the use of some of these techniques in lymphatic muscle biology has somewhat lagged behind those in the endothelium, recent developments in lymphatic muscle contractile and electrical physiology have also led to advances in our understanding of lymphatic transport function, particularly in the regulation of the intrinsic lymph pump. However, much work remains to be done. This paper reviews significant developments in lymphatic biology and discusses areas where further development of lymphatic biology via classical, cellular, and molecular approaches is needed to significantly advance our understanding of lymphatic physiology.

Currently, there is not a standardized protocol to evaluate lymphatic function in women. Therefore, the purpose of this study was to evaluate the effects of arm crank ergometry (AC) and handgrip contractions (HG) on radiopharmaceutical clearance from the hands of six healthy females.On separate days, subjects performed AC (six repeated bouts of arm cranking for 5 min at 0.6 Watts.kilogram(-1) (W.kg(-1)) followed by 5 min rest) or HG (twelve repeated bouts of 75 contractions in 2.5 min at 50% MVC followed by 2.5 min of rest). HG was done with the right hand only while the left hand served as a control (CON). Prior to the start of exercise, (99m)Tc-antimony colloid was injected into the first and fourth finger-web of each hand, and 1 min spot views were taken immediately after the injection and then again every 10 min over 60 min. Clearance from the injection sites was linear and expressed as a slope (% administered activity.min(-1)). Significantly faster clearance was observed with AC (rt = -0.27 +/- 0.03 %.min(-1); left = -0.29 +/- 0.06 %.min(-1)) compared to both HG (-0.18 +/- 0.03 %.min(-1)) and CON (-0.14 +/- 0.05 %.min(-1); p = 0.000).The results indicate that AC may be more effective in promoting lymphatic clearance from the hand and may be a useful protocol to challenge the lymphatic system in breast cancer survivors.

Lymphedema is the term commonly employed to describe the spectrum of pathological states that arise as a consequence of functional lymphatic insufficiency. These human disease entities currently lack an effective cure. Satisfactory therapeutic strategies for both primary and secondary lymphedema will require additional insight into the complex cellular mechanisms and responses that comprise both normal lymphatic function and its regional derangement in states of pathologic dysfunction. Such insights must, initially, be derived from suitable animal models of the chronic human disease process. Historically, efforts to replicate the untreated disease of human lymphedema in animals, through surgery, irradiation, and toxicology, have been fraught with difficulty. The major impediments to the creation of satisfactory animal models have included an inability to reproduce the chronic disease in a stable, reproducible format. Recently, with the promise of potentially successful growth factor-mediated therapeutic lymphangiogenesis, and with the enhanced availability of investigative tools to assess therapeutic responses to molecular therapies, there has been a resurgence of interest in the development of viable animal models of lymphatic insufficiency. Current research has led to the development of genetic and postsurgical models of lymphedema that closely simulate the human conditions of primary and secondary lymphatic insufficiency, respectively. Such models will help to refine the assessment of various therapeutic approaches and their potential applicability to human disease interventions.

Variation in lymphatic function may predispose to development of breast cancer-related lymphoedema. Aims. Breast cancer-related lymphoedema (BCRL) remains a common complication of breast cancer treatment. Many features of this condition remain poorly understood, such as why only approximately 25% of women are affected after similar treatment, and the phenomenon of 'sparing', in which regions of an otherwise swollen arm, most commonly the hand, remain unaffected. This study uses dual-isotope lymphoscintigraphy, involving measurement of rate of clearance of radio-labelled protein from a subcutaneous depot and subsequent appearance in blood, to quantify alterations in lymphatic function in women with BCRL, and to further investigate differences between those in whom the hand is involved with swelling and those in whom it is spared. Methods. Participants received a depot injection of human immunoglobulin G in the dorsum of both hands, labeled with technetium-99m on one side and indium-111 on the other. Rates of clearance from the depot and appearance in venous blood were measured at regular intervals over a 3 h period. Results. A total of 18 women with a history of BCRL were studied. Significant reductions in both depot clearance and venous appearance were observed in the affected arm compared with the unaffected contralateral. control. On sub-group analysis, significant differences were also observed between swollen and spared hand groups, both for the affected and unaffected contralateral arm. Discussion. This study, as well as confirming impaired lymphatic function in arms affected by BCRL, also shows underlying variation in lymphatic function in the unaffected contralateral arm, between those with and without hand sparing. This raises the possibility that the risk of developing BCRL may be, in part, pre-determined. (C) 2004 Elsevier Ltd. All rights reserved.

Quantitative lymphoscintigraphy can be used for investigation of unilateral lymphatic disease of the limbs, such as breast cancer-related lymphoedema (BCRL). Previous studies have compared lymphatic function in the affected limb with that in the unaffected contralateral limb. This study aims to confirm that the assumption of pre-morbid symmetry, never previously demonstrated, is valid. A dual-isotope technique, with bilateral subcutaneous hand injection of polyclonal human immunoglobulin G (HIgG) labelled with either technetium-99m or indium-111, was performed on a total of 37 subjects. The use of two different labels, one for each limb, enabled comparison not only of the rate of clearance from the injection depot, but also of the rate of appearance in venous blood. Results demonstrate clear symmetry between the two arms with respect to both depot clearance and blood appearance rates, as well as the coupling between these two variables. In unilateral lymphatic disease, results of quantitative lymphoscintigraphy should be expressed in relation to the normal arm rather than to an independent control population.

I have been working within tissue viability for nearly 20 years and you cannot work in that field without caring for patients with venous leg ulceration that is associated with chronic oedema. Twenty years ago, we did not have the understanding of chronic oedema and its dangers that we have today. We now realize that chronic oedema in the lower limb can have a tipping point that takes it from simple oedema to a much more serious problem of lymphoedema. Although chronic oedema is not strictly lymphoedema in physiological terms, it is a mixed form of the condition and will lead to deterioration of lymphatic function and will become lymphoedema in time.

Neonatal mice lacking lymphatic vessels due to loss of lymphangiogenic factor CCBE1 or VEGFR3 function fail to inflate their lungs, suggestive of respiratory failure in infants with congenital pulmonary lymphangiectasia., Mammals must inflate their lungs and breathe within minutes of birth to survive. A key regulator of neonatal lung inflation is pulmonary surfactant, a lipoprotein complex which increases lung compliance by reducing alveolar surface tension (Morgan, 1971). Whether other developmental processes also alter lung mechanics in preparation for birth is unknown. We identify prenatal lymphatic function as an unexpected requirement for neonatal lung inflation and respiration. Mice lacking lymphatic vessels, due either to loss of the lymphangiogenic factor CCBE1 or VEGFR3 function, appear cyanotic and die shortly after birth due to failure of lung inflation. Failure of lung inflation is not due to reduced surfactant levels or altered development of the lung but is associated with an elevated wet/dry ratio consistent with edema. Embryonic studies reveal active lymphatic function in the late gestation lung, and significantly reduced total lung compliance in late gestation embryos that lack lymphatics. These findings reveal that lymphatic vascular function plays a previously unrecognized mechanical role in the developing lung that prepares it for inflation at birth. They explain respiratory failure in infants with congenital pulmonary lymphangiectasia, and suggest that inadequate late gestation lymphatic function may also contribute to respiratory failure in premature infants.

The National Institute of Allergy and Infectious Diseases (NIAID) is the primary institute within the National Institutes of Health (NIH) that conducts and supports basic and applied research to better understand, treat, and ultimately prevent infectious, immunologic, and allergic diseases. For more than 60 years, NIAID research has led to new therapies, vaccines, diagnostic tests, and other technologies that have improved the health of millions of people in the United States and around the world.

On November 12, 2012, a group of investigator-scientists was convened to the campus of the National Institutes of Health by the National Institute of Allergy and Infectious Disease (NIAID). In many cases, these individuals were making an acquaintance for the first time. Of great forward-reaching potential, this workshop was devoted to the topic of Lymphatic Function and the Immune Response to Microbial or Viral Infection. The one-day, interactive series of presentations and discussions was the stimulus for lively discussion and the promotion of new investigative ideas. The presentations were far-reaching and varied, encompassing such topics as the influenza virus, viral-endothelial interaction, HIV, lymphatic contractility in the context of immune function, direct chemical analysis of human lymph, lymphatic filariasis, dendritic-endothelial interactions, lymphatic influences on the natural history of pneumonia, and explorations of lymphatic function in mouse models of head and neck inflammation. The general discussions were spirited, embracing such topics as a definition of the knowledge gaps in this topic area, identification of needed research support, and suggestions for an investigative agenda in moving the field forward. The lymphatic system has historically been mistaken as a simple fluid conduit. In the pages of this journal, and elsewhere,1 we have long advocated the concept that the immune functions of the lymphatic system are at least as important as those that contribute to fluid homeostasis. The subject matter of the NIAID-sponsored symposium has, in large measure been embraced by Lymphatic Research and Biology.2–10 Our lymphatic research community is indebted to NIAID for taking a bold and innovative step in organizing the workshop whose proceedings are published in the pages of this issue. Lymphatic Research and Biology is honored to have the opportunity to disseminate this information, especially in light of the stimulus that it is likely to provide for further investigation of immune mechanisms as they relate to the lymphatic circulation.

Despite the common association of filarial infection with elephantiasis, the great majority of those infected are in fact clinically asymptomatic microfilariae carriers. The assumption has been that infection but not disease exists in these presymptomatic persons. In an area Brazil where Wuchereria bancrofti is endemic, flow studies done with dynamic radionuclide lymphoscintigraphy were used to compare 30 limbs from asymptomatic microfilaremic subjects with 16 control limbs. Geometric mean values for T1/2 (19.8 vs. 37.7 min; P < .001), appearance time (7.9 vs. 27.9 min; P < .001), percent uptake at the region of interest (0.67% vs. 0.14%; P < .001), and peak activity (62.6 vs. 2.6 cps; P < .001) each indicated an enhanced pattern of rapid, increased lymph flow in asymptomatic microfilaremic subjects. The abnormal lymphatic function in these subjects indicates that current passive intervention strategies may need to change if the debilitating sequelae of this parasitic infection are to be avoided.

ALFIA (Automated Lymphatic Function Imaging Analysis), an algorithm providing quantitative analysis of investigational near-infrared fluorescence lymphatic images, is described. Images from nine human subjects were analyzed for apparent lymphatic propagation velocities and propulsion periods using manual analysis and ALFIA. While lymphatic propulsion was more easily detected using ALFIA than with manual analysis, statistical analyses indicate no significant difference in the apparent lymphatic velocities although ALFIA tended to calculate longer propulsion periods. With the base ALFIA algorithms validated, further automation can now proceed to provide a clinically relevant analytic tool for quantitatively assessing lymphatic function in humans.

Lymphoscintigraphy using a test involving standing from a supine position and performed following an intradermal injection of 99Tcm-human serum albumin (HSA) was developed to evaluate the function of the lymphatic system in the lower extremities of patients who developed lymphoedema following arterial reconstructive surgery. In normal subjects, the load produced by standing tended to increase lymphatic function as indicated by the frequent appearance of a large spiking wave and a rapid stepwise increase in tracer activity and, less often, a phase of decreasing tracer activity. However, there was either no or less activation of lymph flow following standing in the group which developed leg oedema postoperatively. These findings indicate that lymphatic disruption is responsible for the leg oedema seen in these patients. Performance of this test following an intradermal injection of 99Tcm-HSA is technically simple, requires no special apparatus, and can be completed in 30 min. Lymphoscintigraphy using our new method can provide useful information on abnormalities in lymphatic function.

Red blood cells and lysate products (erythrolysate) are observed consistently in lymph draining acute and chronic inflammatory reactions and from tissues subjected to trauma or surgical procedures. Using hemoglobin as a marker for erythrolysate, we have measured hemoglobin in lymph up to the 10(-6) M range in a number of pathophysiological states. Data demonstrate that erythrolysate alters the pumping characteristics of lymphatic vessels. To test the effects of erythrolysate on lymphatic pumping, bovine lymphatics were suspended in an organ bath preparation with the vessels cannulated at both inflow and outflow ends. By raising the heights of the Krebs reservoir and the outflow catheters appropriately, a transmural pressure that stimulated pumping activity could be applied to the vessels. With a fixed transmural pressure of 6 cm H2O applied to the ducts, sheep erythrolysate depressed pumping activity between 40% and 100%, with dilutions containing between 10(-8) and 10(-5) M hemoglobin. Although the active principle in the red blood cells has not been characterized, evidence from precipitation purification experiments suggests that hemoglobin is an important component. Once suppressed, pumping could be restored in many but not all vessels (often to control levels) by elevating the distending pressure above 6 cm H2O. The relation between transmural pressure and fluid pumping is expressed as a bell-shaped curve, with pumping increasing up to a peak pressure (usually 8 cm H2O) and declining at pressures above this level. By comparing pressure/flow curves, we were able to ascertain that hemoglobin shifted the lymphatic function curve to the right and, on average, reduced the maximum pumping capability of the vessels. We speculate that the presence of erythrolysate/hemoglobin in lymph may modulate the ability of lymphatic vessels to drain liquid and protein from the tissue spaces.

Purpose Lymphatic vessels are critical in interstitial fluid balance, and congenital or acquired derangements lead to accumulation of lymph fluid (lymphedema). Further, when induced by pro-lymphatic growth factors in tumors, they facilitate lymph node metastasis(1). While histological vessel density is counted on tissue sections, there is no method for quantifying lymphatic morphology and patterning in 3-D; key elements in fluid dynamics and cellular interactions that underlie lymphatic function and diseases resulting from alterations to them. We have developed a method to quantify important biological and functional parameters in lymphatics, to help distinguish subtle phenotypic differences and patterning defects. Methods Apical images were taken of whole-mounted mouse ears that were immunofluorescently stained for the lymphatic marker LYVE-1. Key lymphatic parameters were quantified using a computer program we developed. Results Mice with gross lymphedema were found to have significant derangements of many of the key morphological and patterning characteristics assessed. Subtle yet statistically significant lymphatic abnormalities were also identified in less obviously lymphedematous animals. We were also able to assess loco-systemic effects of the pro-lymphatic growth factors. Conclusions Increasing emphasis on lymphatics in disease demands quantification methods that assess key biological and functional parameters. Our method allows comparison and identification of abnormal lymphatic phenotypes and allows assessment of the effects induced by pro-lymphatic growth factors.