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Host-derived succinate accumulates in the airways during bacterial infection. Here, we show that luminal succinate activates murine tracheal brush (tuft) cells through a signaling cascade involving the succinate receptor 1 (SUCNR1), phospholipase Cβ2, and the cation channel transient receptor potential channel subfamily M member 5 (TRPM5). Stimulated brush cells then trigger a long-range Ca 2+ wave spreading radially over the tracheal epithelium through a sequential signaling process. First, brush cells release acetylcholine, which excites nearby cells via muscarinic acetylcholine receptors. From there, the Ca 2+ wave propagates through gap junction signaling, reaching also distant ciliated and secretory cells. These effector cells translate activation into enhanced ciliary activity and Cl - secretion, which are synergistic in boosting mucociliary clearance, the major innate defense mechanism of the airways. Our data establish tracheal brush cells as a central hub in triggering a global epithelial defense program in response to a danger-associated metabolite.

The gallbladder stores bile between meals and empties into the duodenum upon demand and is thereby exposed to the intestinal microbiome. This exposure raises the need for antimicrobial factors, among them, mucins produced by cholangiocytes, the dominant epithelial cell type in the gallbladder. The role of the much less frequent biliary tuft cells is still unknown. We here show that propionate, a major metabolite of intestinal bacteria, activates tuft cells via the short-chain free fatty acid receptor 2 and downstream signaling involving the cation channel transient receptor potential cation channel subfamily M member 5. This results in corelease of acetylcholine and cysteinyl leukotrienes from tuft cells and evokes synergistic paracrine effects upon the epithelium and the gallbladder smooth muscle, respectively. Acetylcholine triggers mucin release from cholangiocytes, an epithelial defense mechanism, through the muscarinic acetylcholine receptor M3. Cysteinyl leukotrienes cause gallbladder contraction through their cognate receptor CysLTR1, prompting emptying and closing. Our results establish gallbladder tuft cells as sensors of the microbial metabolite propionate, initiating dichotomous innate defense mechanisms through simultaneous release of acetylcholine and cysteinyl leukotrienes.

Cholinergic chemosensory cells (CCC) are infrequent epithelial cells with immunosensor function, positioned in mucosal epithelia preferentially near body entry sites in mammals including man. Given their adaptive capacity in response to infection and their role in combatting pathogens, we here addressed the time points of their initial emergence as well as their postnatal development from first exposure to environmental microbiota (i.e., birth) to adulthood in urethra and trachea, utilizing choline acetyltransferase (ChAT)-eGFP reporter mice, mice with genetic deletion of MyD88, toll-like receptor-2 (TLR2), TLR4, TLR2/TLR4, and germ-free mice. Appearance of CCC differs between the investigated organs. CCC of the trachea emerge during embryonic development at E18 and expand further after birth. Urethral CCC show gender diversity and appear first at P6-P10 in male and at P11-P20 in female mice. Urethrae and tracheae of MyD88- and TLR-deficient mice showed significantly fewer CCC in all four investigated deficient strains, with the effect being most prominent in the urethra. In germ-free mice, however, CCC numbers were not reduced, indicating that TLR2/4-MyD88 signaling, but not vita-PAMPs, governs CCC development. Collectively, our data show a marked postnatal expansion of CCC populations with distinct organ-specific features, including the relative impact of TLR2/4-MyD88 signaling. Strong dependency on this pathway (urethra) correlates with absence of CCC at birth and gender-specific initial development and expansion dynamics, whereas moderate dependency (trachea) coincides with presence of first CCC at E18 and sex-independent further development., (© 2021. The Author(s).)

Background: Many discretionary foods ("snacks") contribute both to individual health risks and to global issues, in particular through high carbon footprints and water scarcity. Snacking is influenced by the presence of snacking cues such as food availability, observing others eating, and negative affect. However, less is known about the mechanisms underlying the effects of negative affect. This study examines whether the individual odds of consuming high-calorie snacks as a consequence to being exposed to known snacking cues were moderated by experiencing (i) higher or lower total negative affect per day or (ii) higher or lower negative affect variability per day., Methods: Secondary analysis of an ecological momentary assessment study of 60 participants over 14 days with food logs and randomly timed assessments of known snacking cues. High total daily negative affect levels (daily within-participant means) and negative affect variability (daily within-participant SDs) were examined as moderators to predict high-calorie snacking in three-level hierarchical random effects logistic regressions., Results: Consistent with previous studies, the odds of snacking increased when food was available (OR = 5.05, 95% CI 3.32, 7.66), when others were eating (OR = 5.11, 95% CI = 3.73, 6.99), and when participants experienced more negative affect (OR = 1.02, 95% CI = 1.01, 1.03). Associations for food availability (OR = 0.92, 95% CI 0.86, 0.99) and others eating (OR = 0.95, 95% CI 0.91, 0.99) were significantly moderated by negative affect variability such that associations between cues and high-calorie snacking were weaker on days with higher negative affect variability, but not negative affect levels., Conclusion: The relationship between cues to high-calorie snacking and snacking behavior varies with variability in negative affect, suggesting a complex relationship between affect and high-calorie snacking. Clearer conceptualizations on the relation between affect and eating are needed., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Papadakis, Ferguson and Schüz.)

Mucociliary clearance, the continuous removal of mucus-trapped particles by cilia-driven directed transport of the airway lining fluid, is the primary innate defense mechanism of the airways. It is potently activated by acetylcholine (ACh) addressing muscarinic receptors with a currently less defined role of nicotinic ACh receptors (nAChR). We here set out to determine their contribution in driving ciliary activity in an explanted mouse trachea preparation utilizing selected agonists and antagonists and nAChR-subunit deficient mice. Nicotine (100 µM) induced an increase in ciliary beat frequency, accompanied by a sharp, but not long lasting increase in particle transport speed (PTS) on the mucosal surface showing marked desensitization within the next 30 min. Nicotine-induced PTS acceleration was sensitive to the general nAChR inhibitors mecamylamine and d-tubocurarine as well as to the α3β4-nAChR antagonist α-conotoxin AulB, but not to other antagonists primarily addressing α3β2-nAChR or α4-, α7- and α9-containing nAChR. Agonists at α3β*-nAChR (epibatidine, cytisine), but not cotinine mimicked the effect. Tracheas from mice with genetic deletion of nAChR subunits α5, α7, α9, α10, α9/10, and β2 retained full PTS response to nicotine, whereas this was entirely lost in tracheas from mice lacking the β4-subunit. Collectively, our data show that nicotinic stimulation of α3β4-nAChR acutely increases PTS to the same extent as the established strong activator ATP. In view of the marked desensitization observed in the present setting, the physiological relevance of these receptors in adapting mucociliary clearance to rapidly changing endogenous or environmental stimuli remains open., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Objective: Social factors are among the most powerful and pervasive influences on eating behavior, snacking in particular. Previous research has shown that being in the presence of people who are eating significantly increases the likelihood of eating and affects the types as well as the amount of food consumed. Much less is known about the processes underlying social influence, but previous research has suggested social norms as mediators. In this study, we extended this perspective to everyday settings and examined whether the presence of other people eating leads to a change in perceived momentary norms, and whether this change predicts snack consumption in real life., Method: We applied ecological momentary assessment to study 61 individuals in the normal-obese weight range (M BMI = 24.97 kg/m²; SD = 4.07) over a 14-day monitoring period. We used a combination of event-based snacking reports and randomly timed assessments. The presence of others eating and momentary perceptions of injunctive norms (facets of perceived appropriateness and encouragement) were measured for both assessment types., Results: Mediated, multilevel logistic regression showed that social cues predict snacking (OR = 3.06), and that momentary perceptions of appropriateness (a*b = 0.14) and encouragement (a*b = 0.18) partially mediated these effects., Conclusion: Perceptions of momentary norms mediated the effects of social influence on everyday snacking, which highlights the importance of the social environment for understanding eating behavior. (PsycINFO Database Record, ((c) 2018 APA, all rights reserved).)

Heart valves are highly organized structures determining the direction of blood flow through the heart. Smooth muscle cells within the valve are thought to play an active role during the heart cycle, rather than being just passive flaps. The mature heart valve is composed of extracellular matrix (ECM), various differentiations of valvular interstitial cells (VIC), smooth muscle cells and overlying endothelium. VIC are important for maintaining the structural integrity of the valve, thereby affecting valve function and ECM remodelling. Accumulating evidence suggests an important role of calcitonin receptor-like receptor (CRL) signalling in preventing heart damage under several pathological conditions. Thus we investigate the existence of a putative CRL signalling system in mouse and human heart valves by real-time RT-PCR, laser-assisted microdissection, immunofluorescence and NADPH-diaphorase histochemistry. Mouse and human heart valves expressed mRNAs for the CRL ligands adrenomedullin (AM), adrenomedullin-2 (AM-2) and calcitonin gene-related peptide (CGRP) and for their receptor components, i.e., CRL and receptor-activity-modifying proteins 1-3. Immunofluorescence analysis revealed AM-, AM-2- and CRL-immunolabelling in endothelial cells and VIC, whereas CGRP immunoreactivity was restricted to nerve fibres and some endothelial cells. Nitric oxide synthase activity, as demonstrated by NADPH-diaphorase histochemistry, was shown mainly in valvular endothelial cells in mice, whereas in human aortic valves, VIC and smooth muscle cells were positive. Our results showed the presence of an intrinsic AM/AM-2/CGRP signalling system in murine and human heart valves with distinct cellular localization, suggesting its involvement in the regulation of valve stiffness and ECM production and turnover.

We recently identified a specialized cholinergic cell type in tracheal and urethral epithelium that utilizes molecules of the canonical taste transduction signaling cascade to sense potentially harmful substances in the luminal content. Upon stimulation, this cell initiates protective reflexes. Assuming a sentinel role of such cells at mucosal surfaces exposed to bacteria, we hypothesized their occurrence also in ocular mucosal surfaces. Utilizing a mouse strain expressing eGFP under the promoter of the acetylcholine synthesizing enzyme, choline acetyltransferase (ChAT-eGFP), we observed a cholinergic cell in the murine conjunctiva. Singular cholinergic cells reaching the epithelial surface with slender processes were detected in fornical, but neither in bulbar nor palpebral epithelia. These cells were found neither in the lacrimal canaliculi, nor in the lacrimal sac and the nasolacrimal duct. Cholinergic conjunctival epithelial cells were immunoreactive for components of the canonical taste transduction signaling cascade, i.e. α-gustducin, phospholipase Cβ2 and the monovalent cation channel TRPM5. Calcitonin gene-related peptide- and substance P-immunoreactive sensory nerve fibers were observed extending into the conjunctival epithelium approaching slender ChAT-eGFP-positive cells. In addition, we noted both ChAT-eGFP expression and α-gustducin-immunoreactivity, albeit in different cell populations, in occasionally occurring lymphoid follicles of the nictitating membrane. The data show a previously unidentified cholinergic cell in murine conjunctiva with chemosensory traits that presumably utilizes acetylcholine for signaling. In analogy to similar cells described in the respiratory and urethral epithelium, it might serve to detect bacterial products and to initiate protective reflexes., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Chemosensory cells in the mucosal surface of the respiratory tract ("brush cells") use the canonical taste transduction cascade to detect potentially hazardous content and trigger local protective and aversive respiratory reflexes on stimulation. So far, the urogenital tract has been considered to lack this cell type. Here we report the presence of a previously unidentified cholinergic, polymodal chemosensory cell in the mammalian urethra, the potential portal of entry for bacteria and harmful substances into the urogenital system, but not in further centrally located parts of the urinary tract, such as the bladder, ureter, and renal pelvis. Urethral brush cells express bitter and umami taste receptors and downstream components of the taste transduction cascade; respond to stimulation with bitter (denatonium), umami (monosodium glutamate), and uropathogenic Escherichia coli; and release acetylcholine to communicate with other cells. They are approached by sensory nerve fibers expressing nicotinic acetylcholine receptors, and intraurethral application of denatonium reflexively increases activity of the bladder detrusor muscle in anesthetized rats. We propose a concept of urinary bladder control involving a previously unidentified cholinergic chemosensory cell monitoring the chemical composition of the urethral luminal microenvironment for potential hazardous content.

Introduction: Although endoscopy and angiography have changed the management of lower gastrointestinal bleeding and the majority of patients respond to conservative treatment 10-20% of cases have no recognizable site of hemorrhage. About 10-30% of all patients will require operative intervation. A very rare case of massive lower gastrointestinal bleeding in a young patient who was found to suffer from two causes of gastrointestinal hemorrhage in the same time is reported. The patient had to undergo surgery for the control of bleeding., Case Report: A 23 years old male Greek patient presented to the emergency department of our hospital because of three episodes of hematochezia during the last 10 hours. He was admitted to the surgical department for monitoring of his condition. In the next 10 hours the hematochezia continued and the patient although being transfused with three units of packed red blood cells, started to become unstable with his vital signs affected, having also a syncoptic episode. Emergent colonoscopy could not recognize the site of hemorrhage or any other pathology in the colon, but revealed an intestinal lumen full of blood from the anus to the cecum. It was decided that the patient should undergo operation to stop bleeding. An extensive right hemicolectomy was performed. After that the patient remained stable and showed no signs of hemorrage. The histopathological examination of the specimen showed an arteriovenous malformation but also lesions of the mucosa compatible with early inflammatory bowel disease., Conclusions: In young patients with massive lower gastrointestinal bleeding of unknown origin, extensive right hemicolectomy provides a good and safe therapeutic choice that will control hemorrhage in most cases with the advantage of lower mortality and morbidity rates compared to subtotal colectomy. Close monitoring of the patient postoperatively is essential.

In the epithelium of the lower airways, a cell type of unknown function has been termed "brush cell" because of a distinctive ultrastructural feature, an apical tuft of microvilli. Morphologically similar cells in the nose have been identified as solitary chemosensory cells responding to taste stimuli and triggering trigeminal reflexes. Here we show that brush cells of the mouse trachea express the receptors (Tas2R105, Tas2R108), the downstream signaling molecules (α-gustducin, phospholipase C(β2)) of bitter taste transduction, the synthesis and packaging machinery for acetylcholine, and are addressed by vagal sensory nerve fibers carrying nicotinic acetylcholine receptors. Tracheal application of an nAChR agonist caused a reduction in breathing frequency. Similarly, cycloheximide, a Tas2R108 agonist, evoked a drop in respiratory rate, being sensitive to nicotinic receptor blockade and epithelium removal. This identifies brush cells as cholinergic sensors of the chemical composition of the lower airway luminal microenvironment that are directly linked to the regulation of respiration.

Cancer is often associated with cachexia, cardiovascular symptoms and autonomic dysregulation. We tested whether extracardiac cancer directly affects the innervation of left ventricular myocardium. Mice injected with Lewis lung carcinoma cells (tumor group, TG) or PBS (control group, CG) were analyzed after 21 days. Cardiac function (echocardiography), serum levels of TNF-α and Il-6 (ELISA), structural alterations of cardiomyocytes and their innervation (design-based stereology) and levels of innervation-related mRNA (quantitative RT-PCR) were analysed. The groups did not differ in various functional parameters. Serum levels of TNF-α and Il-6 were elevated in TG. The total length of axons in the left ventricle was reduced. The number of dense core vesicles per axon profile was reduced. Decreased myofibrillar volume, increased sarcoplasmic volume and increased volume of lipid droplets were indicative of metabolic alterations of TG cardiomyocytes. In the heart, the mRNA level of nerve growth factor was reduced whereas that of β1-adrenergic receptor was unchanged in TG. In the stellate ganglion of TG, mRNA levels of nerve growth factor and neuropeptide Y were decreased and that of tyrosine hydroxylase was increased. In summary, cancer induces a systemic pro-inflammatory state, a significant reduction in myocardial innervation and a catabolic phenotype of cardiomyocytes in the mouse. Reduced expression of nerve growth factor may account for the reduced myocardial innervation.

Quantitative information about the innervation is essential to analyze the structure-function relationships of organs. So far, there has been no unbiased stereological tool for this purpose. This study presents a new unbiased and efficient method to quantify the total length of axons in a given reference volume, illustrated on the left ventricle of the mouse heart. The method is based on the following steps: 1) estimation of the reference volume; 2) randomization of location and orientation using appropriate sampling techniques; 3) counting of nerve fiber profiles hit by a defined test area within an unbiased counting frame on paraffin sections stained immunohistochemically for protein gene product 9.5; 4) electron microscopic estimation of the mean number of axon profiles contained in one nerve fiber profile; 5) estimation of the degree of tissue shrinkage of specimens in paraffin; and 6) calculation of the total axon length within the reference volume, taking tissue shrinkage into account. In a set of five mouse hearts, the total length of axons ramifying between cardiomyocytes ranged between approximately 50 and 100 m, with a mean of 75.98 m (SD 23.73). The time required for the microscopical analysis was approximately 8 h/animal for an experienced observer. Using antibodies specific for different neuron subtypes and immunoelectron microscopy, this method is also suited to estimate the total axon length of neurons expressing different transmitters. This new and efficient method is particularly useful when structural remodeling takes place and is suspected to involve gain or loss of axons.

Accumulating evidence suggests a pivotal role of the calcitonin receptor-like receptor (CRLR) signaling pathway in preventing damage of the lung by stabilizing pulmonary barrier function. Intermedin (IMD), also termed adrenomedullin-2, is the most recently identified peptide targeting this receptor. Here we investigated the effect of hypoxia on the expression of IMD in the murine lung and cultured murine pulmonary microvascular endothelial cells (PMEC) as well as the role of IMD in regulating vascular permeability. Monoclonal IMD antibodies were generated, and transcript levels were assayed by quantitative RT-PCR. The promoter region of IMD gene was analyzed, and the effect of hypoxia-inducible factor (HIF)-1alpha on IMD expression was investigated in HEK293T cells. Isolated murine lungs and a human lung microvascular endothelial cell monolayer model were used to study the effect of IMD on vascular permeability. IMD was identified as a pulmonary endothelial peptide by immunohistochemistry and RT-PCR. Hypoxia caused an upregulation of IMD mRNA in the murine lung and PMEC. As shown by these results, HIF-1alpha enhances IMD promoter activity. Our functional studies showed that IMD abolished the increase in pressure-induced endothelial permeability. Moreover, IMD decreased basal and thrombin-induced hyperpermeability of an endothelial cell monolayer in a receptor-dependent manner and activated PKA in these cells. In conclusion, IMD is a novel hypoxia-induced gene and a potential interventional agent for the improvement of endothelial barrier function in systemic inflammatory responses and hypoxia-induced vascular leakage.

Acetylcholine (ACh) is a major regulator of visceral function exerting pharmacologically relevant effects upon smooth muscle tone and epithelial function via five types of muscarinic receptors (M1R-M5R). In this paper, we assessed the specificity of muscarinic receptor (MR) antibodies in immunohistochemical labelling on tissue sections by analysing specimens from wild-type and respective gene-deficient mice. Of 24 antibodies evaluated in this study, 16 were tested at 18 different conditions each, and eight of them in 21 different protocols, resulting in a total number of 456 antibody/protocol combinations. Each of them was tested at four antibody dilutions at minimum, so that finally, at least 1,824 conditions were evaluated. For each of them, dorsal root ganglia, urinary bladder and cross-sections through all thoracic viscera were investigated. In all cases where the antigen was available, at least one incubation condition was identified in which only select cell types were immunolabelled in the positive control but remained unlabelled in the pre-absorption control. With two exceptions (M2R antibodies), however, all antibodies produced identical immunohistochemical labelling patterns in tissues taken from corresponding gene-deficient mice even when the pre-absorption control in wild-type mice suggested specificity. Hence, the present data demonstrate the unpleasant fact that reliable immunohistochemical localisation of MR subtypes with antibodies is the exception rather than the rule. Immunohistochemical detection of MR subtype localisation in tissue sections of peripheral organs is limited to the M2R subtype utilising the most commonly used methodological approaches.

A rare case of isolated giant mesenteric fibromatosis is presented. The tumor originated from the fibrous mesenteric tissue. The patient underwent laparotomy because of abdominal discomfort and sub-occlusive symptoms due to the giant mass. Differential diagnosis of mesenteric masses is discussed and the Authors also review the literature concerning this rare disease.

Endothelial nitric oxide synthase (eNOS), the major nitric oxide (NO)-generating enzyme of the vasculature, is regulated through multiple interactions with proteins, including caveolin-1, Hsp90, Ca2+-calmodulin, and the recently discovered eNOS-interacting protein, NOSIP. Previous studies indicate that NOSIP may contribute to the intricate regulation of eNOS activity and availability. Because eNOS has been shown to be abundantly expressed in the airways, we determined the expression and cellular localization of NOSIP in rat trachea and lung by RT-PCR and immunohistochemistry and examined the interaction of NOSIP with eNOS in lung by coimmunoprecipitation. In tracheal epithelium and lung, NOSIP mRNA expression was prevalent, as shown by RT-PCR, and the corresponding protein interacted with eNOS, as demonstrated by coimmunoprecipitation. Using immunohistochemistry, we found both NOSIP and eNOS immunoreactivity in ciliated epithelial cells of trachea and bronchi, while Clara cells showed immunoreactivity for NOSIP only. NOSIP and eNOS were present in vascular and bronchial smooth muscle cells of large arteries and airways, whereas endothelial cells, as well as bronchiolar and arteriolar smooth muscle cells, exclusively stained for NOSIP. Our results point to functional role(s) of NOSIP in the control of airway and vascular diameter, mucosal secretion, NO synthesis in ciliated epithelium, and, therefore, of mucociliary and bronchial function.

Hodgkin's disease (HD) has been linked to an increase risk of second malignant neoplasms (SMN), especially non-Hodgkin's lymphoma (NHL) and acute nonlymphoblastic leukaemia (ANLL). The mutagenic property of cytotoxic therapy as well as defective immunity have been implicated as playing a major role in the development of SMN in patients previously treated for HD. We report a case of a 14-year-old girl with HD who developed two different second malignancies within a latent period of 28 months following HD diagnosis. The patient presented initially with bilateral cervical and supraclavicular as well as mediastinal and paraaortic lymphadenopathy. She was staged as IIIA, nodular sclerosing type HD, and was given eight alternative cycles of MOPP-ABVD followed by "mantle" field radiotherapy to a total dose of 3.3 Gy plus 0.4 Gy to the upper mediastinum. Within 8 months following the completion of therapy, a period of myelodysplasia and progressive severe immune deficiency, considered as a result of initial treatment, occurred. Eighteen months after HD diagnosis while the patient was continuously neutropenic and heavily immunocompromised, a peripheral T-cell lymphoma of the angiocentric immunoproliferative lesion type (AIL) Grade III, appeared in both lungs within and beyond the radiation field, with no evidence of HD in biopsy specimens. After institution of a new chemotherapy regimen (L17M), a satisfactory response regarding NHL lesions was noted. However, 10 months later the myelodysplastic syndrome (MDS) accompanied by complex chromosomal abnormalities evoluted to frank ANLL with a rapid fatal course. This case supports the hypothesis that combined modality treatment accompanied by severe immunodeficiency may result in the development of multiple second malignancies even within a very short latent period, especially in a subgroup of HD patients who may be particularly increased risk of second cancers.

The present study reports of the geographic distribution of 2,878 cases of uniformly classified malignant lymphomas and of 2,349 similar cases from the literature. Data on histological entities are compared with the geographic and socio-economic characteristics of the regions where they preferentially occur. The results provide three patterns in lymphoma distribution: small cell lymphocytic lymphomas are frequent among populations of European extraction and in farming rather than industrial regions. Lymphomas derived from cells of the germinal center are seen preferentially in so-called "underdeveloped countries", and large cell (immunoblastic) lymphomas appear rather characteristic of industrial areas. Besides genetic influences (rare chronic lymphocytic leukemia (CLL) in Asia as compared to Europe), the results suggest environmental cofactors in the pathogenesis of malignant lymphomas. CLL is more frequent in areas with rather low-dose chronic toxic influences such as from the use of fertilizers and pesticides in farming. Germinal center cell lymphomas tend to occur more frequently in countries with nutritional and hygienic deficiencies with frequent infectious diseases. Large cell high malignancy lymphomas apparently prefer highly industrialized regions with pollution of water supplies by more toxic and immunosuppressive substances.

Two cases of what is apparently Epstein-Barr virus (EBV)-associated atypical lymphoproliferation which clinically suggested malignant lymphoma are discussed. Immunohistology revealed polyclonal T- and B-cell proliferation resembling progressive infectious mononucleosis. Giant cell formation and marked plasmacytosis was suggestive of Hodgkin's disease. EBV serology was initially not diagnostic, but during the course of the disease, elevated titers against early antigens and EBV-associated nuclear antigen suggested virus replication. EBV DNA was demonstrated in lymphoid cells of both cases by in situ hybridization. One case progressed to overt monoclonal B-cell malignant lymphoma. Atypical polyclonal lymphoproliferation in persistent active EBV infection may thus be considered a prelymphomatous condition.

1,292 cases of malignant Non-Hodgkin's lymphomas were classified according to the Rappaport and Kiel classifications and to the New Working Formulation for Clinical Usage (NWF). Subsequently, all lymphoma entities were grouped together following the simple criteria of cell size and growth pattern (small cell, large cell, and mixed cellularity; nodular and diffuse growth). Supplementing these morphological criteria, were data from immunological and cytochemical cell marker studies. The accumulated information was correlated to clinical-prognostic parameters. The results show that using above simplified criteria, all Non-Hodgkin's lymphomas can be classified according to a simple scheme which is of clinical relevance. It can further be deduced from all currently used lymphoma classifications, avoids confusion, and offers abbreviated data useful for computer storage.

Data from morphologic and immunologic follow-up studies are presented of ten patients with AIDS. The sequence of morphologic lesions in lymph nodes proceeds from an initial marked hyperplasia of T- and B-zones (follicular hyperplasia with plasmacytosis and diffuse paracortical hyperplasia) to paracortical atrophy with reactive reticulo-histiocytic hyperplasia and to a late irregular B-cell hyperplasia with effacement of lymph node structure. These changes are accompanied immunocytological by a polyclonal increase in B-Lymphocytes while T-helper cells (TH) and T-suppressor cells (TS) initially exhibit a normal 2:1 ratio, an inversion of the TH/TS ratio is observed in advanced stages. Inversion occurs at the time when paracortical atrophy becomes evident in lymph nodes. Pathogenetically, persistent virus infections and a self-sustaining disturbance of immune regulatory mechanisms are discussed.

Twenty malignant T-cell lymphomas are described in which the initial histological diagnosis was equivocal. Among lymphoma entities initially falsely interpreted on pure morphological grounds were Hodgkin's disease, lymphoepithelioid cellular lymphoma, immunoblastic lymphoma with epithelioid cells, malignant histiocytosis, histiocytosis X, centroblastic lymphoma, undifferentiated carcinoma, and undifferentiated tumour. Variations in the expected mean survival of initially diagnosed tumours and T-cell lymphomas confirm the need for immunohistological cell typing in lymphoma classification.