Current concepts in lymphocyte homing and recirculation

Dietary L-carnitine supplementation modifies blood parameters of mid-lactating dairy cows during standardized lipopolysaccharide-induced inflammation

L-carnitine, available as feed additive, is essential for the beta-oxidation of free fatty acids in the mitochondrial matrix. It provides energy to immune cells and may positively impact the functionality of leukocytes during the acute phase response, a situation of high energy demand. To test this hypothesis, German Holstein cows were assigned to a control group (CON, n = 26) and an L-carnitine supplemented group (CAR, n = 27, rumen-protected L-carnitine product: 125 g/cow/d, corresponded to total L-carnitine intake: 25 g/cow/d, supplied with concentrate) and received an intravenous bolus injection of lipopolysaccharides (LPS, 0.5 µg/kg body weight, E. coli) on day 111 postpartum as a model of standardized systemic inflammation. Blood samples were collected from day 1 ante injectionem until day 14 post injectionem (pi), with frequent sampling through an indwelling venous catheter from 0.5 h pi to 12 h pi. All parameters of the white blood cell count responded significantly to LPS, while only a few parameters were affected by L-carnitine supplementation. The mean eosinophil count, as well as the percentage of basophils were significantly higher in CAR than in CON over time, which may be due to an increased membrane stability. However, phagocytosis and production of reactive oxygen species by leukocytes remained unchanged following L-carnitine supplementation. In conclusion, although supplementation with 25 g L-carnitine per cow and day resulted in increased proportions of specific leukocyte populations, it had only minor effects on the functional parameters studied in mid-lactating dairy cows during LPS-induced inflammation, and there was no evidence of direct improvement of immune functionality.

Theranostic chimeric antigen receptor (CAR)-T cells: Insight into recent trends and challenges in solid tumors

Cell therapy has reached significant milestones in various life-threatening diseases, including cancer. Cell therapy using fluorescent and radiolabeled chimeric antigen receptor (CAR)-T cell is a successful strategy for diagnosing or treating malignancies. Since cell therapy approaches have different results in cancers, the success of hematological cancers has yet to transfer to solid tumor therapy, leading to more casualties. Therefore, there are many areas for improvement in the cell therapy platform. Understanding the therapeutic barriers associated with solid cancers through cell tracking and molecular imaging may provide a platform for effectively delivering CAR-T cells into solid tumors. This review describes CAR-T cells' role in treating solid and non-solid tumors and recent advances. Furthermore, we discuss the main obstacles, mechanism of action, novel strategies and solutions to overcome the challenges from molecular imaging and cell tracking perspectives.

COVID-19 mRNA Vaccines: The Molecular Basis of Some Adverse Events

Each injection of any known vaccine results in a strong expression of pro-inflammatory cytokines. This is the result of the innate immune system activation, without which no adaptive response to the injection of vaccines is possible. Unfortunately, the degree of inflammation produced by COVID-19 mRNA vaccines is variable, probably depending on genetic background and previous immune experiences, which through epigenetic modifications could have made the innate immune system of each individual tolerant or reactive to subsequent immune stimulations.We hypothesize that we can move from a limited pro-inflammatory condition to conditions of increasing expression of pro-inflammatory cytokines that can culminate in multisystem hyperinflammatory syndromes following COVID-19 mRNA vaccines (MIS-V). We have graphically represented this idea in a hypothetical inflammatory pyramid (IP) and we have correlated the time factor to the degree of inflammation produced after the injection of vaccines. Furthermore, we have placed the clinical manifestations within this hypothetical IP, correlating them to the degree of inflammation produced. Surprisingly, excluding the possible presence of an early MIS-V, the time factor and the complexity of clinical manifestations are correlated to the increasing degree of inflammation: symptoms, heart disease and syndromes (MIS-V).

The Influence of Geographical Origin, Age, Sex, and Animal Husbandry on the Spontaneous Histopathology of Laboratory Cynomolgus Macaques (Macaca Fascicularis): A Contemporary Global and Multisite Review of Historical Control Data

To investigate the influence of geographical origin, age, and sex on toxicologically relevant spontaneous histopathology findings in cynomolgus macaques (Macaca fascicularis), we performed a comparative analysis of historical control data (HCD) from 13 test sites that included 3351 animals (1645 females and 1706 males) sourced from Mauritius, China, Vietnam, and Cambodia, aged from 2 to 9.5 years, and from 446 toxicology studies evaluated between 2016 and 2021. The most common findings were mononuclear infiltrates in the kidney, liver, brain, and lung, which showed highest incidences in Mauritian macaques, and heart, salivary glands, and gastrointestinal tract (GIT), which showed highest incidences of mononuclear infiltrates in mainland Asian macaques. Developmental and degenerative findings were more common in Mauritian macaques, while lymphoid hyperplasia and lung pigment showed higher incidences in Asian macaques. Various sex and age-related differences were also present. Despite origin-related differences, the similarities in the nature and distribution of background lesions indicate that macaques from all geographical regions are suitable for toxicity testing and show comparable lesion spectrum. However, in a toxicity study, it is strongly recommended to use animals from a single geographical origin and to follow published guidelines when using HCD to evaluate and interpretate commonly diagnosed spontaneous lesions.

Hallmarks of Resistance to Immune-Checkpoint Inhibitors

Immune-checkpoint inhibitors (ICI), although revolutionary in improving long-term survival outcomes, are mostly effective in patients with immune-responsive tumors. Most patients with cancer either do not respond to ICIs at all or experience disease progression after an initial period of response. Treatment resistance to ICIs remains a major challenge and defines the biggest unmet medical need in oncology worldwide. In a collaborative workshop, thought leaders from academic, biopharma, and nonprofit sectors convened to outline a resistance framework to support and guide future immune-resistance research. Here, we explore the initial part of our effort by collating seminal discoveries through the lens of known biological processes. We highlight eight biological processes and refer to them as immune resistance nodes. We examine the seminal discoveries that define each immune resistance node and pose critical questions, which, if answered, would greatly expand our notion of immune resistance. Ultimately, the expansion and application of this work calls for the integration of multiomic high-dimensional analyses from patient-level data to produce a map of resistance phenotypes that can be utilized to guide effective drug development and improved patient outcomes.

Early drop of circulating T cells negatively correlates with the protective immune response to Yellow Fever vaccination

Lymphocyte recirculation within the human body is essential for efficient pathogen detection and immune responses. So far, immune cell migration has been investigated largely using ovine and murine models, with little evidence in humans. Here, we analyzed peripheral blood of healthy individuals following primary vaccination with the Yellow Fever vaccine YF-17D. We found that the number of leukocytes was transiently and sharply reduced in blood as detected on day 7 after vaccine administration. The T cell drop was restricted to cells expressing the lymph node-homing chemokine receptor CCR7. Interestingly, the vaccine-induced drop positively correlated with the expression of CD69 by the T cells before vaccination. This suggests that CCR7⁺ T cells are being trapped within the lymph nodes through CD69-induced suppression of egress. Strikingly, we further found that the T cell drop negatively correlated with CD8 T cell activation and with production of neutralizing antibodies. In conclusion, early and transient T cell depletion in blood negatively correlated with protective immune response events induced by YF-17D vaccination. Our data highlight baseline CD69 expression and early drop in T cells as potential biomarkers of the Yellow Fever vaccine response.

Zearalenone inhibits T cell chemotaxis by inhibiting cell adhesion and migration related proteins

Zearalenone (ZEA) is a phenolic resorcylic acid lactone mycotoxin produced by several Fusarium species that grow on temperate and tropical crops. The number of reports documenting the immunotoxic effects of ZEA is increasing, but the underlying mechanism is not clear. The purpose of this study was to investigate the effects of ZEA on T cell chemotaxis and evaluate changes in adhesion and migration proteins associated with this process. Specifically, T cells were isolated from BALB/C mouse splenic lymphocytes, activated by concanavalin A (Con A), and then exposed to different concentrations of ZEA. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used observe the ultrastructural changes inside the cell and on the cell surface, respectively. The transwell migration assay was used to evaluate the effect of ZEA on T cell chemotaxis in the presence of CCL19 or CCL21. A confocal 3D laser was used to capture the morphology of perforated cells and western blot was used to detect the expression of proteins associated with cell migration and adhesion. Additionally, we used flow cytometry to examine the expression of chemokine receptors on T cells. Finally, the chemokine (RANTES and MIP-1α) levels secreted by T cells were assessed using cytometric bead array. Overall, our data showed that treatment with ZEA caused ultrastructural damage on the surface as well as inside of T cells. Moreover, ZEA inhibited T cell chemotaxis which was mediated by CCL19 or CCL21 and disrupted the balance of T cell subtypes. The expression of T cell adhesion and migration proteins was also inhibited by ZEA. The expression of T cell chemokine receptor as well as secretion of RANTES and MIP-1α by T cells was suppressed after ZEA treatment. In summary, our results indicate that ZEA reduced the chemotactic effect of T cells mediated by chemokines, which was likely linked to the inhibition of T cell motility and accompanied by decreased expression of adhesion and migration proteins.

T-cell recruitment to the heart: friendly guests or unwelcome visitors?

Myocardial inflammation can lead to lethal acute or chronic heart failure (HF). T lymphocytes (T cells), have been reported in the inflamed heart in different etiologies of HF, and more recent studies support that different T-cell subsets play distinct roles in the heart depending on the inflammation-triggering event. T cells follow sequential steps to extravasate into tissues, but their specific recruitment to the heart is determined by several factors. These include differences in T-cell responsiveness to specific chemokines in the heart environment, as well as differences in the expression of adhesion molecules in response to distinct stimuli, which regulate T-cell recruitment to the heart and have consequences in cardiac remodeling and function. This review focuses on recent advances in our understanding of the role T cells play in the heart, including its critical role for host defense to virus and myocardial healing postischemia, and its pathogenic role in chronic ischemic and nonischemic HF. We discuss a variety of mechanisms that contribute to the inflammatory damage to the heart, as well as regulatory mechanisms that limit the magnitude of T-cell-mediated inflammation. We also highlight areas in which further research is needed to understand the role T cells play in the heart and distinguish the findings reported in experimental animal models and how they may translate to clinical observations in the human heart.

Effects of arterial blood on the venous blood vessel wall and differences in percentages of lymphocytes and neutrophils between arterial and venous blood

Vascular sclerosis mostly occurs in arteries and is mainly related to anatomic structure and hemodynamics of artery. This study aimed to investigate effects of arterial blood on vein wall and explore differences of composition between arterial and venous blood.Ultrasound was used to examine the distal venous structure of arteriovenous fistula in uremia patients. Immunohistochemistry was used to study the pathology of the distal vein. Twelve patients were divided into control group and trial group. Patients received an arteriovenous fistula within 1 month in control group. Patients had undergone this surgery ≥2 years before in the trial group. Blood samples were collected from the aortic, arterial, and venous vessels of 51 patients who had taken coronary angiography and analyzed with blood routine rest, biochemical, and immunological measures to compare the differences of blood composition between artery and vein. This study was registered with the China Clinical Trial Center website under registration number ChiCTR-OOC-16008085.In the trial group, the vascular wall of distal veins of fistula were thickened and hardened. No significant differences of blood composition were found between the aortic and radial arterial blood. However, the differences in the percentages of lymphocytes and neutrophils between arterial and venous blood were significant (Pa = .0095, Pb = .01).Under smooth hemodynamic conditions, arterial blood caused hardening of the venous wall. Arterial and venous blood differed in the percentage of lymphocyte and neutrophils. This may contribute to the vascular sclerosis that is observed in arteries more often than veins.

Applications of chemokines as adjuvants for vaccine immunotherapy

Vaccinations are expected to aid in building immunity against pathogens. This objective often requires the addition of an adjuvant with certain vaccine formulations containing weakly immunogenic antigens. Adjuvants can improve antigen processing, presentation, and recognition, thereby improving the immunogenicity of a vaccine by simulating and eliciting an immune response. Chemokines are a group of small chemoattractant proteins that are essential regulators of the immune system. They are involved in almost every aspect of tumorigenesis, antitumor immunity, and antimicrobial activity and also play a critical role in regulating innate and adaptive immune responses. More recently, chemokines have been used as vaccine adjuvants due to their ability to modulate lymphocyte development, priming and effector functions, and enhance protective immunity. Chemokines that are produced naturally by the body's own immune system could serve as potentially safer and more reliable adjuvant options versus synthetic adjuvants. This review will primarily focus on chemokines and their immunomodulatory activities against various infectious diseases and cancers.

A Mathematical Model to Predict HIV Virological Failure and Elucidate the Role of Lymph Node Drug Penetration

Preventing virological failure following HIV treatment remains a difficult task that is further complicated by the emergence of drug resistance. We have developed a mathematical model able to explain and predict HIV virological outcomes for various compounds and patients' drug intake patterns. Compared to current approaches, this model considers, altogether, drug penetration into lymph nodes, a refined adherence representation accounting for the propensity for long drug holidays, population pharmacokinetic and pharmacodynamic variability, drug interaction, and crossresistance. In silico results are consistent with clinical observations for treatment with efavirenz, efavirenz in association with tenofovir DF and emtricitabine, or boosted darunavir. Our findings indicate that limited lymph node drug penetration can account for a large proportion of cases of virological failure and drug resistance. Since a limited amount of information is required by the model, it can be of use in the process of drug discovery and to guide clinical treatment strategies.

Mechanisms of T cell organotropism

Protective immunity relies upon T cell differentiation and subsequent migration to target tissues. Similarly, immune homeostasis requires the localization of regulatory T cells (Tregs) to the sites where immunity takes place. While naïve T lymphocytes recirculate predominantly in secondary lymphoid tissue, primed T cells and activated Tregs must traffic to the antigen rich non-lymphoid tissue to exert effector and regulatory responses, respectively. Following priming in draining lymph nodes, T cells acquire the 'homing receptors' to facilitate their access to specific tissues and organs. An additional level of topographic specificity is provided by T cells receptor recognition of antigen displayed by the endothelium. Furthermore, co-stimulatory signals (such as those induced by CD28) have been shown not only to regulate T cell activation and differentiation, but also to orchestrate the anatomy of the ensuing T cell response. We here review the molecular mechanisms supporting trafficking of both effector and regulatory T cells to specific antigen-rich tissues.

Derangements of lacrimal drainage-associated lymphoid tissue (LDALT) in human chronic dacryocystitis

AIMS

To study the changes in the lacrimal drainage-associated lymphoid tissue of the lacrimal sac in human chronic dacryocystitis and its possible implications in understanding the immune defense mechanisms and etiopathogenesis of primary acquired nasolacrimal duct obstruction.

METHODS

Retrospective interventional study involving 200 lacrimal sacs of 164 consecutive patients seen between July 2009 and July 2012. Data collected include demographics, clinical presentation, laterality, age at presentation, duration of symptoms, diagnostic irrigation, indications for a dacyrocystectomy, pattern and severity of lymphoid infiltrate, types of lymphoid follicles and their locations, plasma cells, and other cellular infiltrates. The associated epithelial, stromal, and luminal changes with an emphasis on acini, mucosal glands, blood vessels, lymphatics, and goblet cells were also noted. Immunohistochemistry using CD3, CD20, CD138, and immunoglobulin A were used to substantiate the lymphoid tissues of the lacrimal sac.

RESULTS

A total of 200 lacrimal sacs were obtained from dacryocystectomy of 164 patients. The patients included 60.5% (99/164) females and 39.6% (65/164) males, with a mean age of 58.4 years at presentation. Laterality showed a predominance of left lacrimal sacs (55%, 110/200) as compared to the right lacrimal sacs (45%, 90/200). Symptoms of epiphora and discharge of more than 6 months duration were considered to be chronic. Lymphoid infiltrate pattern was diffuse in majority of the sacs (81%, 162/200), with subepithelial and intraepithelial together being the commonest location (46.5%, 93/200). Distinct lymphoid follicles were seen in 28% (56/200). Most of the sacs showed mild plasma cell infiltration (66.5%, 133/200). IgA-rich secretions were noted in the lumen and the lining epithelium in 34.5% (69/200). Other common changes noted include increase in the goblet cells (82%, 164/200), dilated lymphatics (94%, 188/200), proliferating blood vessels (99%, 198/200), thickened epithelium (54.5%, 109/200), and stromal fibrosis (88%, 176/200).

CONCLUSION

This study presents the largest series to date (n = 200 lacrimal sacs) exclusively on changes in lacrimal drainage-associated lymphoid tissue in human chronic dacryocystitis. This study could be the starting point for further exploration into the molecular biology, immunological implications, and possible implications of LDALT derangements on etiopathogenesis of primary acquired nasolacrimal duct obstruction.

Activation of EphA receptors on CD4+CD45RO+ memory cells stimulates migration

We have demonstrated previously that binding of ephrin-A1 to EphA receptors on human CD4(+) and CD8(+) T cells stimulates migration. Two EphA receptors have been reported in T cells: EphA1 at the protein level and EphA4 at the mRNA level. In this study, we wanted to investigate the expression profile of these receptors in T cell subpopulations and to test if expression differences would affect the potential of cells to migrate upon ephrin-A1 binding. We have generated an anti-EphA4 mAb for expression analysis. Our data show that functional EphA4 is expressed on the cell surface of CD4(+) and CD8(+) T cells. In addition, EphA4 receptor expression is induced after overnight incubation in serum-free medium, in particular, on CD4(+)CD45RO(+) T cells. Migration of CD4(+) T cells in response to ephrin-A1 is observed for memory cells (CD45RO(+)) and much weaker for naïve cells (CD45RA(+)). A signaling complex associated with the EphA4 receptor has also been isolated and includes EphA1, the Src family kinases Fyn and Lck, Slp76, and Vav1. To conclude, T cells express EphA1 and EphA4 receptors. Expression differences of EphA4 are observed in subpopulations of CD4(+) T cells. This is related to the cell migration potential after ephrin-A1 binding.

Non-equilibrium and differential function between intraepithelial and lamina propria virus-specific TCRalphabeta(+) CD8alphabeta(+) T cells in the small intestinal mucosa

The gastrointestinal mucosa regularly encounters commensal and pathogenic microbiota. Gut mucosal lymphocytes consist of two phenotypically different populations residing in the intestinal intraepithelial (IEL) compartment and lamina propria (LP). Little is known about compositional and functional differences of antigen-specific T cells from these mucosal compartments after mucosal infection, or the degree of trafficking between them. We here studied the B8R(20-27)-specific CD8 T-cell response in LP and IEL compartments after intrarectal immunization with modified vaccinia virus Ankara (MVA). CD8(+) T cells in the IEL compartment had much lower avidity than in the LP or spleen during acute and memory phases. Surprisingly, the TCR Vbeta-chain distribution of antigen-specific T cells and the length of the CDR3 region of the dominant Vbeta genes showed substantial dissimilarities between IEL and LP antigen-specific CD8alphabeta T cells in individual mice, increasing with time. We show functional and compositional differences between these mucosal compartments during the effector and memory phases of the immune response, indicating limited crosstalk and microenvironmental differences between the IEL, LP, and spleen. The restricted migration of cells from each of these mucosal compartments could partly account for a founder effect we observed in the IEL TCRalphabeta CD8alphabeta epitope-specific repertoire that might impact protective efficacy.

Immunopathogenesis of IgAN

The defining hallmark of IgA nephropathy (IgAN) is deposition of polymeric IgA1 in the glomerular mesangium accompanied by a mesangial proliferative glomerulonephritis. The mechanisms involved in mesangial polymeric IgA1 deposition and the initiation of inflammatory glomerular injury remain unclear. This lack of a complete understanding of the pathogenesis of IgAN has meant that there is still no treatment known to modify mesangial deposition of IgA. Increasing evidence, however, supports the importance of IgA-containing immune complex formation as a pivotal factor driving mesangial IgA deposition and triggering of glomerular injury. A number of potentially important changes to the IgA1 molecule have been identified in IgAN, which may contribute to immune complex formation. These changes suggest that the polymeric IgA1 that deposits in IgA nephropathy is derived from mucosally primed plasma cells. The presence of this IgA in the circulation reflects displacement of mucosal B lineage cells to systemic sites and may be the result of mishoming of lymphocytes trafficking along the mucosa-bone marrow axis.

Statins inhibit lymphocyte homing to peripheral lymph nodes

Lymphocyte homing to peripheral lymph nodes is governed by adhesion molecules, including lymphocyte function-associated antigen 1 (LFA-1). Statins are 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors and exert anti-inflammatory effects, e.g. inhibition of LFA-1. It is still not known whether statin compounds are capable of inhibiting lymphocyte homing in vivo. We used a cervical lymph node preparation to study the effects of simvastatin on lymphocyte adhesion to high endothelial venules (HEVs) by means of intravital fluorescence microscopy (IVM). IVM revealed that firm adhesion of lymphocytes to HEV endothelium critically depends on the adhesive function of LFA-1. The number of firmly adherent lymphocytes was reduced by 58% in LFA-1-deficient mice (P < 0.05 versus wild-type controls). As in mutant mice, acute treatment with simvastatin (i.p. injection at 2 hr prior to IVM) inhibited the firm adhesion of lymphocytes to HEV endothelium of wild-type animals by 63% (P < 0.05 versus vehicle-treated wild-type controls). In addition, acute treatment with the synthetic statin-derivate LFA878 also reduced firm lymphocyte adhesion in HEVs by 63% (P > 0.05 versus placebo-treated controls). Histological analysis after a 10-day treatment with simvastatin showed reduced cellularity of cervical lymph nodes, as indicated by a reduction of the relative area of haematoxylin-stained cell nuclei in cervical lymph node cross-sections from 94 +/- 0% in vehicle-treated controls to 77 +/- 3% in simvastatin-treated mice (P < 0.05). We conclude that statin compounds are capable of inhibiting lymphocyte homing to murine peripheral lymph nodes in vivo. This may have novel implications for the treatment of adaptive immune responses, e.g. transplant rejection.

Adenosine 5'-triphosphate and adenosine as endogenous signaling molecules in immunity and inflammation

Human health is under constant threat of a wide variety of dangers, both self and nonself. The immune system is occupied with protecting the host against such dangers in order to preserve human health. For that purpose, the immune system is equipped with a diverse array of both cellular and non-cellular effectors that are in continuous communication with each other. The naturally occurring nucleotide adenosine 5'-triphosphate (ATP) and its metabolite adenosine (Ado) probably constitute an intrinsic part of this extensive immunological network through purinergic signaling by their cognate receptors, which are widely expressed throughout the body. This review provides a thorough overview of the effects of ATP and Ado on major immune cell types. The overwhelming evidence indicates that ATP and Ado are important endogenous signaling molecules in immunity and inflammation. Although the role of ATP and Ado during the course of inflammatory and immune responses in vivo appears to be extremely complex, we propose that their immunological role is both interdependent and multifaceted, meaning that the nature of their effects may shift from immunostimulatory to immunoregulatory or vice versa depending on extracellular concentrations as well as on expression patterns of purinergic receptors and ecto-enzymes. Purinergic signaling thus contributes to the fine-tuning of inflammatory and immune responses in such a way that the danger to the host is eliminated efficiently with minimal damage to healthy tissues.

Successful implantation of intravenously administered stem cells correlates with severity of inflammation in murine myocarditis

The present study was designed to determine whether cardiac inflammation is important for the successful homing of stem cells to the heart after intravenous injection in a murine myocarditis model. Male Bagg albino/c mice were infected with encephalomyocarditis virus (EMCV) to produce myocarditis. Subgroups of mice received single injections by tail vein of embryonic stem cells (ESCs) transfected with green fluorescent protein (GFP) as a marker at days 3, 14, or 60 after infection; other subgroups without stem cell injections were killed at each of these time points to assess the degree of inflammation present. The surviving mice were killed at day 90 after virus infection and hemodynamics, gross pathology, histology, and inflammatory cytokine production in the hearts were measured. Our results indicate that myocardial inflammation was most severe and cytokine production highest at day 14 after EMCV inoculation, and in particular, was strongly positive for interleukin 6. Mice receiving intravenous ESC injections on day 14 after EMCV inoculation showed the largest number of GFP-positive cells at the time of death and the greatest functional improvement compared to uninfected controls without inflammation. We conclude that factors released from myocardium during inflammation are important for enhancing the homing, migration, and implantation of systemically infused stem cells.

Adherence of Hodgkin's disease-derived cell lines to the various lymph node compartments

This adherence study was performed to clarify the trafficking of Hodgkin-Reed-Sternberg (HRS) cells in Hodgkin's disease (HD) and thus try to unravel the peculiar pathways of dissemination in the early stages of this malignant neoplasm. Using non-neoplastic human necropsy or biopsy lymph node as well as tonsillar tissue sections, we have studied the adherence of the KMH-2 and L-428 HD-derived cell lines and have compared it to that of peripheral blood lymphocytes (PBLs). In necropsy lymph nodes, cell lines predominantly adhered to sinuses and paracortex, whilst adhered PBLs were distributed more widely. In biopsy lymph nodes, adhesion to high endothelial venules (HEVs) was rarely observed, whilst cell lines were found to adhere to sinuses. Inhibition by EDTA pretreatment affected adherence to HEVs as well as to sinuses and paracortex to a similar degree. Our findings point to the possible importance of the lymph node sinuses and paracortex in relation to homing of the HRS cells and their dissemination during the early stages of HD. The results suggest a significant primary role of the extracellular matrix of the paracortex and sinuses in the homing of HRS cells, with the HEVs of only secondary importance.

Platelet endothelial cell adhesion molecule-1 is expressed in adenoidal crypt epithelial cells

The adenoidal epithelial crypt is a potential site of antigen transport from pharyngeal lumen to adenoidal tissue. The base of the crypt is consistently infiltrated with leucocytes, forming a reticular lymphoepithelial structure. To evaluate mechanisms that possibly mediate leucocyte infiltration, expressions of leucocyte adhesion molecules, such as platelet endothelial cell adhesion molecule-1 (PECAM-1) (CD31), vascular cell adhesion molecule-1 (VCAM-1) (CD106) and intercellular adhesion molecule-1 (ICAM-1) (CD54), were studied in the adenoidal epithelial crypt. Epithelial cells in the outer opening of the adenoidal crypt were positive for VCAM-1, whereas epithelial cells at the base of the crypt were positive for PECAM-1. Isolated ICAM-1-expressing cells were found throughout the epithelial crypt. Double immunofluorescence staining revealed that the epithelial cells positive for PECAM-1 or VCAM-1 were positive for cytokeratin. The expression of PECAM-1 in the base and VCAM-1 at the orifice of the adenoidal epithelial crypt implies that the base and the orifice of the crypt have a distinct ability to recruit leucocytes. Epithelial cells expressing PECAM-1 may have a role in the formation of the reticular lymphoepithelial structure in the epithelial crypt.

A 3D numerical study of the effect of channel height on leukocyte deformation and adhesion in parallel-plate flow chambers

The effect of channel height on leukocyte adhesion to a lower plate in a parallel-plate flow chamber is studied by direct numerical simulations in three dimensions. The numerical model takes into account deformability and viscoelasticity of the leukocyte, membrane ruffles (microvilli), and the presence of mechanically different regions inside the cell (nucleus and cytoplasm). Leukocyte adhesion is assumed to be mediated by interactions of adhesion molecules on the tips of microvilli with their counterparts on the lower plate. Results of this study indicate that an adherent leukocyte experiences much less drag than a rigid sphere due to its deformation and transient stress growth. While overall leukocyte deformation is modest at shear stresses encountered in the microcirculation, deformation in the contact region is significant. At fixed wall shear stress, the contact area of the cell membrane with the substrate increases with increasing the ratio of cell diameter to channel height, leading to greater adhesion. This suggests that in vitro flow chamber studies typically underestimate leukocyte adhesion that occurs in the microcirculation.

Pathogenesis of IgA nephropathy

In IgA nephropathy (IgAN), there is dysregulation of the IgA response to a wide range of antigens. The dysregulation promotes synthesis of polymeric IgA1 (pIgA1) with physicochemical characteristics that favor mesangial deposition, including altered O-glycosylation of the hinge region. This may be the synthesis of IgA in the systemic compartment, which has the phenotype of mucosal IgA. There is not a change in IgA1 structure to an entirely abnormal form; rather, there is a shift that results in a proportional increase in forms of IgA1 also found in healthy individuals. Altered O-glycosylation could favor pIgA1 deposition by promoting formation of macromolecular IgA and immune complexes. Mesangial injury follows through interactions of pIgA1 with the cells and extracellular matrix proteins of the mesangium and the activation of complement. The final clinical expression of IgAN also depends on generic factors, including hypertension and proteinuria, and a fibrotic renal response. No single "IgAN gene" has been identified, and it is likely that multiple interacting genes will eventually prove to underlie susceptibility to IgAN and the risk of progressive renal disease. These new pathogenic insights have not yet led to new therapeutic opportunities.

Disseminated tumor cells homing into rats' liver: a new possible mechanism of HCC recurrence

AIM

To detect the origin of hepatocellular carcinoma (HCC) recurring and attempt to propose a new recurrent mechanism.

METHODS

Orthotopic liver allotransplantation was performed on male rats with HCC- induced by diethylnitrosamine using female donors. Metastatic tumors in transplanted livers were obtained. A DNA probe that exhibits specificity for the rat Y chromosome was generated by using a set of primers specific to murine sry gene. In situ hybridization (ISH) for Y chromosome was used to detected the origin of HCC recurring. Male HCC tissue was designed to be positive control. ISH on female tissue and using non-labeled with DIG probe was thought to be negative control.

RESULTS

Positive marks were seen through ISH for Y chromosome in recurrent tumor tissue and positive control. No signal was detected in both negative controls.

CONCLUSION

Recurrent HCC after liver transplantation originated from disseminated tumor cells in recipients. Extrahepatic cells homing into liver may be a new HCC recurrence mechanism. Likewise, it implicates that this mechanism is responsible for HCC recurring after hepatectomy.

Lymphoid distribution in the migratory gull Larus ridibundus

We studied the distribution of lymphocytes in the main lymphoid tissues (blood, spleen and thymus) of the gull Larus ridibundus, searching for variations that might depend on the migratory cycle. We also looked for sex- and age-associated differences in lymphoid redistribution. In L. ridibundus, lymphocytes are the most commonly observed leukocyte subpopulation in blood. Moreover, changes in the distribution of lymphocytes in the lymphoid tissue occur, depending on the migratory period. The proportion of these cells in spleen is greater in the post-migratory and pre-migratory periods compared to the non-migratory period. The percentages of circulating lymphocytes are high in the pre-migratory period, but depletion occurs in the post-migratory period. In contrast, the age or the sex of the animals did not confer any major differences on the lymphoid distribution.

Coevolution of markers of innate and adaptive immunity in skin and peripheral blood of patients with erythema migrans

We used multiparameter flow cytometry to characterize leukocyte immunophenotypes and cytokines in skin and peripheral blood of patients with erythema migrans (EM). Dermal leukocytes and cytokines were assessed in fluids aspirated from epidermal suction blisters raised over EM lesions and skin of uninfected controls. Compared with corresponding peripheral blood, EM infiltrates were enriched for T cells, monocytes/macrophages, and dendritic cells (DCs), contained lower proportions of neutrophils, and were virtually devoid of B cells. Enhanced expression of CD14 and HLA-DR by lesional neutrophils and macrophages indicated that these innate effector cells were highly activated. Staining for CD45RO and CD27 revealed that lesional T lymphocytes were predominantly Ag-experienced cells; furthermore, a subset of circulating T cells also appeared to be neosensitized. Lesional DC subsets, CD11c(+) (monocytoid) and CD11c(-) (plasmacytoid), expressed activation/maturation surface markers. Patients with multiple EM lesions had greater symptom scores and higher serum levels of IFN-alpha, TNF-alpha, and IL-2 than patients with solitary EM. IL-6 and IFN-gamma were the predominant cytokines in EM lesions; however, greater levels of both mediators were detected in blister fluids from patients with isolated EM. Circulating monocytes displayed significant increases in surface expression of Toll-like receptor (TLR)1 and TLR2, while CD11c(+) DCs showed increased expression of TLR2 and TLR4; lesional macrophages and CD11c(+) and CD11c(-) DCs exhibited increases in expression of all three TLRs. These results demonstrate that Borrelia burgdorferi triggers innate and adaptive responses during early Lyme disease and emphasize the interdependence of these two arms of the immune response in the efforts of the host to contain spirochetal infection.

Ephrin stimulation modulates T cell chemotaxis

Eph receptor tyrosine kinases and their ligands, the ephrins, are known to play an important role in regulating cell migration and targeting in neuronal and endothelial cells. Recently, it has been shown that lymphoid cells also express Eph receptors, raising the possibility that Eph receptors may similarly regulate lymphocyte migration. Chemotaxis in response to soluble chemokine factors is an essential facet of T cell biology. We demonstrate here that T cell chemotaxis in response to both the stromal cell-derived factor (SDF)-1alpha and macrophage inflammatory protein 3beta chemokines is modulated by costimulation with ephrins. Both ephrin-A and ephrin-B ligands were found to modify the chemotactic responses of a T cell line and primary T cells. Ephrin-A1, in particular, strongly inhibited chemotaxis. In accordance with the tyrosine kinase activity of EphA receptors, ephrin-A1 stimulation induced rapid intracellular tyrosine phosphorylation in T cells. Although strongly inhibiting chemotaxis, ephrin-A1 costimulus did not affect many of the signaling events downstream of the SDF-1alpha receptor CXCR4, including calcium flux and activation of MAPK. Rather, ephrin-A1 altered the balance of small G protein activity in T cells. Ephrin-A1 stimulation prevented SDF-1alpha-induced activation of cdc42, while simultaneously inducing rho activation. Ultimately, ephrin-A1 was found to inhibit chemokine-induced actin polymerization, thereby blocking migration. Ubiquitous ephrin expression in vivo creates enormous potential for T cells to encounter these ligands, suggesting that Eph receptors and ephrins may be important regulators of T cell migration.

Cloning of human junctional adhesion molecule 3 (JAM3) and its identification as the JAM2 counter-receptor

We have identified a third member of the junctional adhesion molecule (JAM) family. At the protein level JAM3 displays 36 and 32% identity to JAM2 and JAM1, respectively. The coding region is distributed over 9 exons and maps to chromosome 11q25. The gene shows widespread tissue expression with higher levels apparent in the kidney, brain, and placenta. At the cellular level we show expression of JAM3 transcript within endothelial cells. Our major finding is that JAM3 and JAM2 are binding partners. Thus, JAM3 ectodomain binds firmly to JAM2-Fc. This heterotypic interaction is maintained when JAM3-Fc is used to capture Chinese hamster ovary cells expressing full-length JAM2. In static adhesion assays we show that JAM3 is unable to bind to leukocyte cell lines. This is consistent with the lack of JAM2 expression. However, using JAM2-Fc pull-down experiments in combination with polyclonal anti-JAM3 serum, we demonstrate that JAM3 is the previously uncharacterized 43-kDa counter-receptor that mediates JAM2 adhesion to T cells. Most significantly we demonstrate up-regulation of JAM3 protein on peripheral blood lymphocytes following activation. Finally we show the utility of JAM3 ectodomain as an inhibitor of JAM2 adhesion.