Altered Expression of Intestinal Tight Junctions in Patients with Chronic Kidney Disease: A Pathogenetic Mechanism of Intestinal Hyperpermeability.

BACKGROUND: Systemic inflammation in chronic kidney disease (CKD) is associated (as a cause or effect) with intestinal barrier dysfunction and increased gut permeability, with mechanisms not yet fully understood. This study investigated different parameters of the intestinal barrier in CKD patients, especially tight junction (TJ) proteins and their possible association with systemic endotoxemia and inflammation. METHODS: Thirty-three patients with stage I-IV CKD (n = 17) or end-stage kidney disease (ESKD) (n = 16) and 11 healthy controls underwent duodenal biopsy. Samples were examined histologically, the presence of CD3+ T-lymphocytes and the expression of occludin and claudin-1 in the intestinal epithelium was evaluated by means of immunohistochemistry, circulating endotoxin concentrations were determined by means of ELISA and the concentrations of the cytokines IL-1ß, IL-6, IL-8, IL-10 and TNF-α in serum were measured using flow cytometry. RESULTS: Patients with stage I-IV CKD or ESKD had significantly higher serum endotoxin, IL-6, IL-8 and IL-10 levels compared to controls. Intestinal occludin and claudin-1 were significantly decreased, and their expression was inversely correlated with systemic endotoxemia. Regarding occludin, a specific expression pattern was observed, with a gradually increasing loss of its expression from the crypt to the tip of the villi. CONCLUSION: The expression of occludin and claudin-1 in enterocytes is significantly reduced in patients with CKD, contributing to systemic endotoxemia and inflammatory responses in these patients.

Altered Expression of Intestinal Tight Junction Proteins in Heart Failure Patients with Reduced or Preserved Ejection Fraction: A Pathogenetic Mechanism of Intestinal Hyperpermeability.

Although intestinal microbiota alterations (dysbiosis) have been described in heart failure (HF) patients, the possible mechanisms of intestinal barrier dysfunction leading to endotoxemia and systemic inflammation are not fully understood. In this study, we investigated the expression of the intestinal tight junction (TJ) proteins occludin and claudin-1 in patients with HF with reduced (HFrEF) or preserved ejection fraction (HFpEF) and their possible association with systemic endotoxemia and inflammation. Ten healthy controls and twenty-eight patients with HF (HFrEF (n = 14), HFpEF (n = 14)) underwent duodenal biopsy. Histological parameters were recorded, intraepithelial CD3+ T-cells and the expression of occludin and claudin-1 in enterocytes were examined using immunohistochemistry, circulating endotoxin concentrations were determined using ELISA, and concentrations of cytokines were determined using flow cytometry. Patients with HFrEF or HFpEF had significantly higher serum endotoxin concentrations (p < 0.001), a significantly decreased intestinal occludin and claudin-1 expression (in HfrEF p < 0.01 for occludin, p < 0.05 for claudin-1, in HfpEF p < 0.01 occludin and claudin-1), and significantly increased serum concentrations of IL-6, IL-8, and IL-10 (for IL-6 and IL-10, p < 0.05 for HFrEF and p < 0.001 for HFpEF; and for IL-8, p < 0.05 for both groups) compared to controls. Occludin and claudin-1 expression inversely correlated with systemic endotoxemia (p < 0.05 and p < 0.01, respectively). Heart failure, regardless of the type of ejection fraction, results in a significant decrease in enterocytic occludin and claudin-1 expression, which may represent an important cellular mechanism for the intestinal barrier dysfunction causing systemic endotoxemia and inflammatory response.

Patterns, Cost, and Immunological Response of MDR vs. Non MDR-Bacteremia: A Prospective Cohort Study.

BACKGROUND: Antimicrobial resistance (AMR) is a significant global health concern, posing a critical challenge for the effective management of infectious diseases. This study aimed to compare the immunological response, clinical outcomes, and associated costs in patients with bacteremia due to antibiotic-resistant vs. susceptible bacterial microorganisms. METHODS: This study was a single-center, prospective cohort study conducted from May 2017 to November 2019. The study population consisted of patients admitted with a confirmed diagnosis of bacteremia. RESULTS: A total of 116 patients were included, with 53 (45.7%) harboring non-multidrug-resistant (non-MDR) bacterial isolates and 63 (54.3%) harboring multidrug-resistant (MDR) bacterial isolates. Patients with MDR bacteremia had more severe clinical presentations, as indicated by higher SOFA and APACHE II scores. Results revealed higher all-cause mortality rates (39.7% vs. 17%) and median healthcare costs (€4791 vs. €2843.5) in the MDR bacteremia group. Moreover, MDR bacteremia was linked to higher levels of TNF-a, indicating a differential immune response. Furthermore, MDR bacteremia was found to be an independent predictor of mortality (OR = 3.216, 95% CI: 1.338-7.730, p = 0.009) and increased healthcare costs (effect size of approximately 27.4%). CONCLUSION: These findings underscore the significant impact of antimicrobial resistance in healthcare settings, highlighting the urgency of addressing the challenges posed by MDR microorganisms.

The Influence of Single Nucleotide Polymorphisms on Vitamin D Receptor Protein Levels and Function in Chronic Liver Disease.

Single nucleotide polymorphisms (SNPs) in the vitamin D receptor (VDR) gene have been associated with chronic liver disease. We investigated the role of VDR SNPs on VDR protein levels and function in patients with chronic liver disease. VDR expression levels were determined in peripheral T lymphocytes (CD3+VDR+), monocytes (CD14+VDR+), and plasma from patients (n = 66) and healthy controls (n = 38). Genotyping of SNPs and the determination of expression of VDR/vitamin D-related genes were performed by using qPCR. The effect of FokI SNP on vitamin D-binding to VDR was investigated by molecular dynamics simulations. CD14+VDR+ cells were correlated with the MELD score. The ApaI SNP was associated with decreased CD3+VDR+ levels in cirrhotic patients and with higher liver stiffness in HCV patients. The BsmI and TaqI SNPs were associated with increased VDR plasma concentrations in cirrhotic patients and decreased CD14+VDR+ levels in HCV patients. The FokI SNP was associated with increased CD3+VDR+ levels in cirrhotic patients and controls. VDR polymorphisms were significantly related to the expression of genes critical for normal hepatocyte function and immune homeostasis. VDR expression levels were related to the clinical severity of liver disease. VDR SNPs may be related to the progression of chronic liver disease by affecting VDR expression levels.

Shifting gears: Study of immune system parameters of male habitual marathon runners.

Aim: Marathon is a running event in which athletes must cover a distance of 42.195 km. In addition to participating in marathons, marathoners have incorporated extensive running into their lifestyle. In the present study, we investigated the effect of long-term strenuous exercise in the form of marathon running on the immune system. Methods & Results: We collected peripheral blood samples from 37 male marathoners before/after a race and 37 age/sex/body mass index (BMI)-matched healthy sedentary controls. Hematological and biochemical tests revealed race-induced leukocytosis attributable to neutrophilia and significant increases in plasma lactate dehydrogenase (LDH), creatine phosphokinase (CPK), and cortisol concentrations. Phenotypic analysis of lymphocytes revealed race-induced significant decrease in the number of lymphocytes, memory helper T (Th) cells, naive, memory and activated cytotoxic T (Tc) cells, natural killer (NK), NKT, and B1 cells, and a significant increase in the number of activated Th and regulatory Th cells (Tregs). Compared with controls, marathoners maintained significantly lower levels of memory and activated Th cells and higher levels of activated Tc and B1 cells. Measurement of plasma cytokine levels revealed a pro-inflammatory cytokine polarization that increased after the race. Examination of gene expression of cytokines and Th-cell signature transcription factors in peripheral blood mononuclear cells revealed a significant decrease in tumor necrosis factor α (TNF-α) and interleukin (IL)-17, and a significant increase in IL-6, IL-10 and forkhead box P3 (FoxP3) after the race. Compared with controls, marathoners maintained significantly higher levels of TNF-α. Assessment of the suppressive capacity of Tregs in co-cultures of isolated effector Th cells and Tregs showed significantly increased suppressive capacity of marathoners' Tregs after the race. Conclusions: Compared with controls, marathoners live with permanent changes in certain immune parameters. Marathoners exhibit a stable pro-inflammatory cytokine polarization that increases after the race and is counterbalanced by increased numbers of Tregs overexpressing FoxP3 and having increased suppressive capacity.

Synergistic effect of cold atmospheric pressure plasma and free or liposomal doxorubicin on melanoma cells.

The aim of the present study was to investigate combined effects of cold atmospheric plasma (CAP) and the chemotherapeutic drug doxorubicin (DOX) on murine and human melanoma cells, and normal cells. In addition to free drug, the combination of CAP with a liposomal drug (DOX-LIP) was also studied for the first time. Thiazolyl blue tetrazolium bromide (MTT) and Trypan Blue exclusion assays were used to evaluate cell viability; the mechanism of cell death was evaluated by flow cytometry. Combined treatment effects on the clonogenic capability of melanoma cells, was also tested with soft agar colony formation assay. Furthermore the effect of CAP on the cellular uptake of DOX or DOX-LIP was examined. Results showed a strong synergistic effect of CAP and DOX or DOX-LIP on selectively decreasing cell viability of melanoma cells. CAP accelerated the apoptotic effect of DOX (or DOX-LIP) and dramatically reduced the aggressiveness of melanoma cells, as the combination treatment significantly decreased their anchorage independent growth. Moreover, CAP did not result in increased cellular uptake of DOX under the present experimental conditions. In conclusion, CAP facilitates DOX cytotoxic effects on melanoma cells, and affects their metastatic potential by reducing their clonogenicity, as shown for the first time.

Intestinal Barrier Biomarker ZO1 and Endotoxin Are Increased in Blood of Patients With COVID-19-associated Pneumonia.

BACKGROUND/AIM: The present study was undertaken to investigate (i) whether hospitalized patients with COVID-19 pneumonia present intestinal barrier dysfunction with consequent translocation of endotoxin into the systemic circulation and (ii) whether intestinal barrier biomarkers have any prognostic role in terms of progression to severe respiratory failure. PATIENTS AND METHODS: In this prospective study, 22 patients with COVID-19-associated pneumonia and 19 patients with non-COVID-19-related community-acquired pneumonia (CAP group) were studied while 12 healthy persons comprised the control group. Blood samples were collected on admission and analysed for serum levels of endotoxin and zonula occludens-1 (ZO1). Clinical courses regarding progression to severe respiratory failure (SRF) requiring mechanical ventilation were recorded. RESULTS: Patients with COVID-19-associated pneumonia and patients with CAP presented significantly higher serum endotoxin and ZO1 concentrations on admission as compared to healthy controls. There was no difference in endotoxin levels between patients with COVID-19-related pneumonia and patients with CAP. In patients with COVID-19-related pneumonia, serum endotoxin concentrations were positively correlated with C-reactive protein and ferritin values. There were no significant differences in serum endotoxin and ZO1 concentrations between patients with severe and not severe COVID-19-related pneumonia, nor between patients who developed SRF and those who did not Conclusion: Patients with COVID-19-related pneumonia present intestinal barrier dysfunction leading to systemic endotoxemia. Admission values of endotoxin and ZO1 do not have any prognostic role for progression to SRF.

Fecal Microbiota Transplantation and Hydrocortisone Ameliorate Intestinal Barrier Dysfunction and Improve Survival in a Rat Model of Cecal Ligation and Puncture-Induced Sepsis.

INTRODUCTION: Sepsis is a life-threatening syndrome which can progress to multiple organ dysfunction with high mortality. Intestinal barrier failure exerts a central role in the pathophysiological sequence of events that lead from sepsis to multiple organ dysfunction. The present study investigated the role of hydrocortisone (HC) administration and fecal microbiota transplantation (FMT) in several parameters of the gut barrier integrity, immune activation, and survival, in a model of polymicrobial sepsis in rats. METHODS: Forty adults male Wistar rats were randomly divided into four groups: sham (group I), cecal ligation and puncture (CLP) (group II), CLP + HC (2.8 mg/kg, intraperitoneally single dose at 6 h) (group III), and CLP + FMT at 6 h (group IV). At 24 h post-CLP, ileal tissues were harvested for histological and immunohistochemical analyses while endotoxin, IL-6, and IL-10 levels in systemic circulation were determined. In a second experiment the same groups were observed for 7 days for mortality, with daily administration of hydrocortisone (group III) and FMT (group IV) in surviving rats. RESULTS: HC administration and FMT significantly reduced mortality of septic rats by 50%. These interventions totally reversed intestinal mucosal atrophy by increasing villous density and mucosal thickness (µm, mean ±â€ŠSD: Group I: 620 ±â€Š35, Group II: 411 ±â€Š52, Group III: 622 ±â€Š19, Group IV: 617 ±â€Š44). HC and FMT reduced the apoptotic body count in intestinal crypts whereas these increased the mitotic/apoptotic index. Activated caspase-3 expression in intestinal crypts was significantly reduced by HC or FMT (activated caspase-3 (+) enterocytes/10 crypts, mean ±â€ŠSD: Group I: 1.6 ±â€Š0.5, Group II: 5.8 ±â€Š2.4, Group III: 3.6 ±â€Š0.9, Group IV: 2.3 ±â€Š0.6). Both treatments increased Paneth cell count and decreased intraepithelial CD3(+) T lymphocytes and inflammatory infiltration of lamina propria to control levels. In the sham group almost the total of intestinal epithelial cells expressed occludin (92 ±â€Š8%) and claudin-1 (98 ±â€Š4%) and CLP reduced this expression to 34 ±â€Š12% for occludin and 35 ±â€Š7% for claudin-1. Administration of HC significantly increased occludin (51 ±â€Š17%) and claudin-1 (77 ±â€Š9%) expression. FMT exerted also a significant restoring effect in tight junction by increasing occludin (56 ±â€Š15%) and claudin-1 (84 ±â€Š7%) expression. The beneficial effects of these treatments on gut barrier function led to significant reduction of systemic endotoxemia (EU/mL, mean ±â€ŠSD: Group I: 0.93 ±â€Š0.36, Group II: 2.14 ±â€Š1.74, Group III: 1.48 ±â€Š0.53, Group IV: 1.61 ±â€Š0.58), while FMT additionally decreased IL-6 and IL-10 levels. CONCLUSION: Fecal microbiota transplantation and stress dose hydrocortisone administration in septic rats induce a multifactorial improvement of the gut mechanical and immunological barriers, preventing endotoxemia and leading to improved survival.

Conditioning attenuates kidney and heart injury in rats following transient suprarenal occlusion of the abdominal aorta.

Suprarenal aortic clamping during abdominal aortic aneurysm (AAA) repair results in ischemia-reperfusion injury (IRI) in local (i.e. kidney) and distant (i.e. heart) tissue. To investigate perioperative approaches that mitigate IRI-induced tissue damage, Wistar rats underwent suprarenal aortic clamping either alone or in combination with short cycles of ischemic conditioning before and/or after clamping. Serum analysis revealed significant reduction in key biochemical parameters reflecting decreased tissue damage at systemic level and improved renal function in conditioned groups compared to controls (p < 0.05), which was corroborated by histolopathological evaluation. Importantly, the levels of DNA damage, as reflected by the biomarkers 8-oxo-G, γH2AX and pATM were reduced in conditioned versus non-conditioned cases. In this setting, NADPH oxidase, a source of free radicals, decreased in the myocardium of conditioned cases. Of note, administration of 5-HD and 8-SPT blocking key protective signaling routes abrogated the salutary effect of conditioning. To further understand the non-targeted effect of IRI on the heart, it was noted that serum TGF-ß1 levels decreased in conditioned groups, whereas this difference was eliminated after 5-HD and 8-SPT administration. Collectively, conditioning strategies reduced both renal and myocardial injury. Additionally, the present study highlights TGF-ß1 as an attractive target for manipulation in this context.

The Prognostic Value of Endotoxemia and Intestinal Barrier Biomarker ZO-1 in Bacteremic Sepsis.

BACKGROUND: Intestinal barrier dysfunction exerts a pivotal pathophysiological role in the development of multiple organ dysfunction in sepsis. The present study was undertaken to investigate the potential role of serum intestinal fatty acid-binding protein (I-FABP) and zonula occludens-1 (ZO-1) levels as biomarkers of intestinal barrier dysfunction in bacteremic sepsis. METHODS: Seventy-five patients with bacteremic sepsis of abdominal origin (n = 34) or nonabdominal origin (n = 41) and 12 healthy controls were retrospectively studied. Blood samples collected upon sepsis diagnosis were analyzed for serum ZO-1, I-FABP and endotoxin levels. Prognostic scores Sequential Organ Failure Assessment (SOFA), quickSOFA and Acute Physiology and Chronic Health Evaluation (APACHE-II) were determined over the first 24 hours after sepsis diagnosis and patients' outcome in terms of 28-day mortality was recorded. RESULTS: Serum ZO-1 levels were significantly higher in bacteremic septic patients as compared to controls with no difference between patients with abdominal or extra-abdominal source of infection. Serum I-FABP levels were significantly lower in septic patients as compared to control and this reduction was more evident in patients with bacteremic abdominal sepsis. Serum ZO-1 and endotoxin concentrations were found significantly higher in patients who did not survive from sepsis. In receiver operating characteristic curve analysis, both endotoxin and ZO-1 predicted 28-day mortality. In addition, ZO-1 and endotoxin were correlated with the prognostic scores of qSOFA, SOFA and APACHE II. CONCLUSIONS: The results of this study indicate that serum ZO-1 might be a reliable biomarker of gut barrier dysfunction in sepsis, not affected by the abdominal or extra-abdominal site of infection. ZO-1, measured early at sepsis diagnosis, might represent a valuable additional prognostic tool for patients' outcome.

Metabolic Association between Leptin and the Corticotropin Releasing Hormone.

OBJECTIVE: In healthy individuals, leptin is produced from adipose tissue and is secreted into the circulation to communicate energy balance status to the brain and control fat metabolism. Corticotropin- Releasing Hormone (CRH) is synthesized in the hypothalamus and regulates stress responses. Among the many adipokines and hormones that control fat metabolism, leptin and CRH both curb appetite and inhibit food intake. Despite numerous reports on leptin and CRH properties and function, little has been actually shown about their association in the adipose tissue environment. METHODS: In this article, we summarized the salient information on leptin and CRH in relation to metabolism. We also investigated the direct effect of recombinant CRH on leptin secretion by primary cultures of human adipocytes isolated from subcutaneous abdominal adipose tissue of 7 healthy children and adolescents, and measured CRH and leptin levels in plasma collected from peripheral blood of 24 healthy children and adolescents to assess whether a correlation exists between CRH and leptin levels in the periphery. RESULTS AND CONCLUSION: The available data indicate that CRH exerts a role in the regulation of leptin in human adipocytes. We show that CRH downregulates leptin production by mature adipocytes and that a strong negative correlation exists between CRH and leptin levels in the periphery, and suggest the possible mechanisms of CRH control of leptin. Delineation of CRH control of leptin production by adipocytes may explain unknown pathogenic mechanisms linking stress and metabolism.

Clinical and immunological parameters of Sjögren's syndrome.

Sjögren's syndrome (SS) is a chronic autoimmune disease that primarily affects the exocrine glands, resulting in their functional impairment. In SS, lymphocytic infiltration of salivary and lacrimal glands, and deposition of several types of autoantibodies, mainly anti-SS-A (anti-Ro) and anti-SS-B (anti-La), lead to chronic inflammation, with xerostomia and keratoconjunctivitis sicca. In its primary form (pSS), SS does not involve additional connective tissue diseases, whereas in its secondary and more common form (sSS), SS presents in association with other rheumatic autoimmune diseases, mainly rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and systemic sclerosis (SSc). As in most autoimmune diseases, environmental, hormonal and genetic factors are implicated in SS pathogenesis. In SS T cells predominate in mild lesions, whereas B cells predominate in advanced lesions. Th1, Th2, Th17, follicular helper T (Tfh) cells and regulatory cells (Tregs/Bregs), with their characteristic cytokine profiles, have been implicated in the pathogenesis of SS. It has been suggested that Th1 and Th17 cells initiate SS and, as the disease progresses, Th2 and Tfh cells predominate. It is assumed that, as in all autoimmune and inflammatory conditions, tolerance defects contribute to SS pathogenesis. It is intriguing that in SS it remains unclear which types of regulatory cells are functional and whether they ameliorate or worsen the disease. In this review we present a comprehensive update on SS with emphasis on immune system involvement, and suggest new insights into SS immunopathogenesis.

Regulatory Cell Populations in Relapsing-Remitting Multiple Sclerosis (RRMS) Patients: Effect of Disease Activity and Treatment Regimens.

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS) of autoimmune etiology that results from an imbalance between CNS-specific T effector cells and peripheral suppressive mechanisms mediated by regulatory cells (RC). In this research, we collected blood samples from 83 relapsing remitting MS (RRMS) patients and 45 healthy persons (HC), to assess the sizes of their RC populations, including CD4⁺CD25(high)Foxp3⁺ (nTregs), CD3⁺CD4⁺HLA(-)G⁺, CD3⁺CD8⁺CD28(-), CD3⁺CD56⁺, and CD56(bright) cells, and how RC are affected by disease activity (acute phase or remission) and types of treatment (methylprednisolone, interferon, or natalizumab). In addition, we isolated peripheral blood mononuclear cells (PBMC) and cultured them with peptides mapping to myelin antigens, to determine RC responsiveness to autoantigens. The results showed decreased levels of nTregs in patients in the acute phase ± methylprednisolone and in remission + natalizumab, but HC levels in patients in remission or receiving interferon. Patients + interferon had the highest levels of CD3⁺CD4⁺HLA(-)G⁺ and CD3⁺CD8⁺CD28(-) RC, and patients in the acute phase + methylprednisolone the lowest. Patients in remission had the highest levels of CD3⁺CD56⁺, and patients in remission + natalizumab the highest levels of CD56(bright) cells. Only nTregs responded to autoantigens in culture, regardless of disease activity or treatment. The highest suppressive activity was exhibited by nTregs from patients in remission. In conclusion, in RRMS disease activity and type of treatment affect different RC populations. nTregs respond to myelin antigens, indicating that it is possible to restore immunological tolerance through nTreg induction.

Effect of dendritic cell state and antigen-presentation conditions on resulting T-cell phenotypes and Th cytokine profiles.

T cells play a pivotal role in controlling the immune response and have been the focus of extensive research. We studied the process of in vitro generation of antigen-specific T effector cells (Teffs) to assess the dynamics of antigen presentation and determine the best conditions for cell therapy. We used a peptidic construct consisting of combined HLA class I and II epitopes of the tumor antigen MAGE-3 as an antigen. Monocytes were isolated from healthy donors and were differentiated to dendritic cells (DCs) in vitro. The peptide was added to the DC culture, the pulsed cells were transferred to a co-culture with lymphocytes from the same donor, either as irradiated feeders or untreated, and were cultured in the presence or absence of IL-2. Several rounds of restimulation followed. The cells were analyzed by Flow Cytometry, and cytokine levels were measured by ELISA and Cytometric Bead Array for Th1/Th2/Th17 profiling. The results showed that the lymphocytes in culture upregulated their activation markers and produced Th1 proinflammatory cytokines in response to the peptide, optimally when it was presented by non-irradiated dendritic cells in the presence of IL-2. In contrast, DC irradiation resulted in low activation potential and a shift toward a suppressive phenotype. After prolonged antigenic stimulation, the culture displayed Th17 polarization. In conclusion, the functional integrity of DCs is necessary for the development of antigen-specific Teffs, and culture conditions can be developed to create Teffs with specific properties for eventual use in cell therapy applications.

Expression patterns of leptin receptor (OB-R) isoforms and direct in vitro effects of recombinant leptin on OB-R, leptin expression and cytokine secretion by human hematopoietic malignant cells.

Several studies have implicated leptin in the pathophysiology of neoplasias. We investigated the direct effect of leptin on malignant hematopoietic tissue that included: primary acute myeloid leukemia (AML) cells, leukemic cell lines and bone marrow biopsies from multiple myeloma (MM) patients. PBMC, T-cells, B-cells and monocytes from healthy subjects served as controls. We defined the patterns of OB-R isoform expression in AML cells and leukemic cell lines in comparison to control cells by RT-PCR. rLeptin upregulated the expression of OB-R and endogenous leptin in AML blasts and certain cell lines but not in control cells. Cytometric Bead Array analysis of pro- and anti-inflammatory cytokines showed that rleptin upregulates IL-6 secretion by AML cells, various cytokines by the leukemic cell lines tested and IL-10 secretion by control PBMC, contributed by monocytes. Western immunoblotting revealed that the effect of rleptin was independent of JAK-2/phospho-JAK-2 protein levels. Finally, MM biopsies stained positive for leptin and, to a lesser extend, OB-R. Immunoreactivity was confined mostly to the nucleus of the myeloma cells. Normal myelocytes, promyelocytes and megakaryocytes stained weakly positive, and erythroid cells were constantly negative. We propose that the leptin/OB-R system is strongly and directly involved in supporting the growth of hematopoietic malignancies.