Leukocyte-cell adhesion: a molecular process fundamental in leukocyte physiology

Recapitulation of pathophysiological features of AD in SARS-CoV-2-infected subjects

Infection with the etiological agent of COVID-19, SARS-CoV-2, appears capable of impacting cognition in some patients with post-acute sequelae of SARS-CoV-2 (PASC). To evaluate neuropathophysiological consequences of SARS-CoV-2 infection, we examine transcriptional and cellular signatures in the Brodmann area 9 (BA9) of the frontal cortex and the hippocampal formation (HF) in SARS-CoV-2, Alzheimer's disease (AD), and SARS-CoV-2-infected AD individuals compared to age- and gender-matched neurological cases. Here, we show similar alterations of neuroinflammation and blood-brain barrier integrity in SARS-CoV-2, AD, and SARS-CoV-2-infected AD individuals. Distribution of microglial changes reflected by the increase in Iba-1 reveals nodular morphological alterations in SARS-CoV-2-infected AD individuals. Similarly, HIF-1α is significantly upregulated in the context of SARS-CoV-2 infection in the same brain regions regardless of AD status. The finding may help in informing decision-making regarding therapeutic treatments in patients with neuro-PASC, especially those at increased risk of developing AD.

Molecular and cellular similarities in the brain of SARS-CoV-2 and Alzheimer's disease individuals

Infection with the etiological agent of COVID-19, SARS-CoV-2, appears capable of impacting cognition, which some patients with Post-acute Sequelae of SARS-CoV-2 (PASC). To evaluate neuro-pathophysiological consequences of SARS-CoV-2 infection, we examine transcriptional and cellular signatures in the Broadman area 9 (BA9) of the frontal cortex and the hippocampal formation (HF) in SARS-CoV-2, Alzheimer's disease (AD) and SARS-CoV-2 infected AD individuals, compared to age- and gender-matched neurological cases. Here we show similar alterations of neuroinflammation and blood-brain barrier integrity in SARS-CoV-2, AD, and SARS-CoV-2 infected AD individuals. Distribution of microglial changes reflected by the increase of Iba-1 reveal nodular morphological alterations in SARS-CoV-2 infected AD individuals. Similarly, HIF-1α is significantly upregulated in the context of SARS-CoV-2 infection in the same brain regions regardless of AD status. The finding may help to inform decision-making regarding therapeutic treatments in patients with neuro-PASC, especially those at increased risk of developing AD.

TEASER

SARS-CoV-2 and Alzheimer's disease share similar neuroinflammatory processes, which may help explain neuro-PASC.

Effects of different routes of endotoxin injury on barrier function in alcoholic lung syndrome

In the lung, chronic alcohol consumption is a risk factor for acute respiratory distress syndrome (ARDS), a disorder that can be fatal due to airspace flooding. The severity of pulmonary edema is controlled by multiple barriers, and in particular the alveolar epithelial barrier and pulmonary microvasculature. However, to date, the effects of chronic alcohol ingestion on both of these barriers in the lung has not been directly and simultaneously measured. In addition the effects of alcohol on systemic, indirect lung injury versus direct injury have not been compared. In this study, we used tissue morphometry and Evans Blue permeability assays to assess the effects of alcohol and endotoxemia injury on pulmonary barrier function comparing intraperitoneal (IP) administration of lipopolysaccharide (LPS) to intratracheal (IT) administration. Consistent with previous reports, we found that in alcohol-fed mice, the alveolar barrier was impaired, allowing Evans Blue to permeate into the airspaces. Moreover, IT administered LPS caused a significant breach of both the alveolar epithelial and vascular barriers in alcohol-fed mice, whereas the endothelial barrier was less affected in response to IP administered LPS. The alveolar barrier of control mice remained intact for both IP and IT administered LPS. However, both injuries caused significant interstitial edema, independently of whether the mice were fed alcohol or not. These data suggest that in order to properly target pulmonary edema due to alcoholic lung syndrome, both the alveolar and endothelial barriers need to be considered as well as the nature of the "second hit" that initiates ARDS.

Expression and localization of absent in melanoma 2 in the injured spinal cord

In traumatic brain injury, absent in melanoma 2 (AIM2) has been demonstrated to be involved in pyroptotic neuronal cell death. Although the pathophysiological mechanism of spinal cord injury is similar to that of brain injury, the expression and cellular localization of AIM2 after spinal cord injury is still not very clear. In the present study, we used a rat model of T9 spinal cord contusive injury, produced using the weight drop method. The rats were randomly divided into 1-hour, 6-hour, 1-day, 3-day and 6-day (post-injury time points) groups. Sham-operated rats only received laminectomy at T9 without contusive injury. Western blot assay revealed that the expression levels of AIM2 were not significantly different among the 1-hour, 6-hour and 1-day groups. The expression levels of AIM2 were markedly higher in the 1-hour, 6-hour and 1-day groups compared with the sham, 3-day and 7-day groups. Double immunofluorescence staining demonstrated that AIM2 was expressed by NeuN⁺ (neurons), GFAP⁺ (astrocytes), CNPase⁺ (oligodendrocytes) and CD11b⁺ (microglia) cells in the sham-operated spinal cord. In rats with spinal cord injury, AIM2 was also found in CD45⁺ (leukocytes) and CD68⁺ (activated microglia/macrophages) cells in the spinal cord at all time points. These findings indicate that AIM2 is mainly expressed in neurons, astrocytes, microglia and oligodendrocytes in the normal spinal cord, and that after spinal cord injury, its expression increases because of the infiltration of leukocytes and the activation of astrocytes and microglia/macrophages.

CEA and NCA Expressed by Colon Carcinoma Cells Affect their Interaction with and Lysability by Activated Lymphocytes

Heterogeneous lysability by interleukin-2 activated lymphocytes (LAK) and other immune effectors was observed in the human colon-carcinoma lines LoVo/Dx, LoVo/H and HT29. The tumor cells with high susceptibility to LAK (LoVo/Dx, HT29) expressed higher amounts of the adhesion molecules ICAMl, LFA3 and NCA/CEA than cells with low LAK sensitivity (LoVo/H). Monoclonal antibodies against these molecules caused a marked reduction of lysis by LAK of LoVo/Dx and HT29. A pool of these antibodies induced a nearly complete inhibition of the LAK lysis of both lines. Treatment of LoVo/Dx with differentiating agents (dimethylformamide and retinoic acid) led to a decreased expression of the adhesion molecules, including NCA, accompanied by increased resistance to LAK-mediated lysis. Moreover, the presence of CEA soluble antigen drastically inhibited the cytotoxic activity of LAK effectors against HT29 and LoVo/Dx cells, in a dose-dependent manner. These data indicate that sensitivity of colon-carcinoma cells to activated lymphocytes depends on the level of expression of adhesion molecules, including CEA and NCA. Given the role of CEA-related antigens in tumor/lymphocyte interaction, soluble CEA, frequently released by colon-carcinoma, may be involved in immunosuppressive effects induced in vivo by tumor cells.

The effect of ALA-PDT under normoxia and cobalt chloride (CoCl2)-induced hypoxia on adhesion molecules (ICAM-1, VCAM-1) secretion by colorectal cancer cells

BACKGROUND

The most fundamental problem in cancer biology research is to understand the mechanisms of cancer cell resistance to oncological therapies. Literature reports emphasize the important role of adhesion molecules: intercellular adhesion molecule 1 and vascular cell adhesion molecule 1 (ICAM-1 and VCAM-1) in cancer progression and resistance to treatment. Photodynamic therapy (PDT) could become the component of a personalized approach to colorectal cancer, therefore we examined the effects of ALA (δ-aminolevulinic) acid PDT in normoxia and under cobalt chloride (CoCl₂)-induced hypoxia on ICAM-1 and VCAM-1 secretion by colorectal cancer cells.

METHODS

Human colorectal cancer cells of different malignant potential SW480 and SW620 were used in the experiment. Cell lines were treated ALA, in order to achieve conditions comparable to in vivo hypoxia, CoCl₂ was added, then cells were irradiated both in normoxia and in hypoxia-like conditions. Cell viability was assessed using the LDH and MTT assays and apoptosis. ICAM-1 and VCAM-1 concentrations were determined with the Bio - Plex ProTM Assay and System.

RESULTS

The experiment revealed that ALA PDT under normoxia and CoCl₂-induced hypoxia had no significant effect on ICAM-1 and VCAM-1-dependent adhesion of colorectal cancer cells. The secretion of ICAM-1 by SW480 ell line was more pronounced compared to ICAM-1 secretion by SW620 cells.

CONCLUSION

Determination of tumor marker levels and especially adhesion molecules involved in metastatic spread is necessary. Our experiment reveals, that ALA PDT in normoxia and CoCl₂-induced hypoxia has no effect on adhesion molecules secretion by colon cancer cells in vitro.

Adhesion characteristics of nano/micro-sized particles with dual ligands with different interaction distances

Dual ligand conjugated particle for targeted delivery. Rotational dislodging force on the ligand–receptor interaction. Optimal receptor and ligand ratio exist.

Human CD34(+) progenitor hematopoiesis in liquid culture for in vitro assessment of drug-induced myelotoxicity

Utilization of validated CFU-GM assays for myelotoxicity screening is hampered by its labor-intensive and low-throughput nature. Herein, we transformed the defined CFU-GM assay conditions and IC90 endpoint into a higher throughput format. Human CD34(+) hematopoietic progenitors were cultured in a 96-well plate for 14 days with the same cytokine (rhGM-CSF) used in the CFU-GM assay. Expansion and differentiation toward myeloid lineages were manifested by characteristic changes in nuclear and cytoplasmic morphology and by temporal expression patterns of CD34, CD11b and CD13 markers. Inhibition of CD34(+) cell myelopoiesis by 12 anticancer drugs known to induce myelotoxicity in the clinic was quantifiable using either general cytotoxicity endpoints (cell growth area or total nucleus count) or lineage specific readouts (count of cells expressing CD11b and/or CD13). The IC50 and IC90 values derived from the concentration-response curves of 14-day drug exposure in CD34(+) cell culture were highly correlated with those from the international validation study of the CFU-GM assay, demonstrating capability to assess general cytotoxicity, cell proliferation and myelopoiesis simultaneously. These results suggest that this human CD34(+) hematopoietic progenitor cell assay can be used as a direct replacement for the validated, low throughput CFU-GM assay, and could expand application of in vitro myelotoxicity testing.

Reduced Fluorescence versus Forward Scatter Time-of-Flight and Increased Peak versus Integral Fluorescence Ratios Indicate Receptor Clustering in Flow Cytometry

Clustering of surface receptors is often required to initiate signal transduction, receptor internalization, and cellular activation. To study the kinetics of clustering, we developed an economic high-throughput method using flow cytometry. The quantification of receptor clustering by flow cytometry is based on the following two observations: first, the fluorescence signal length (FL time-of-flight [ToF]) decreases relative to the forward scatter signal length (FSc-ToF), and second, the peak FL (FL-peak) increases relative to the integral FL (FL-integral) upon clustering of FL-labeled surface receptors. Receptor macroclustering can therefore be quantified using the ratios FL-ToF/FSc-ToF (method ToF) or FL-peak/FL-integral (method Peak). We have used these methods to analyze clustering of two immune receptors known to undergo different conformational and oligomeric states: the BCR and the complement receptor 3 (CR3), on murine splenocytes, purified B cells, and human neutrophils. Engagement of both the BCR and CR3, on immortalized as well as primary murine B cells and human neutrophil, respectively, resulted in decreased FL-ToF/FSc-ToF and increased FL-peak/FL-integral ratios. Manipulation of the actin-myosin cytoskeleton altered BCR clustering which could be measured using the established parameters. To confirm clustering of CR3 on neutrophils, we applied imaging flow cytometry. Because receptor engagement is as a biological process dependent on cell viability, energy metabolism, and temperature, receptor clustering can only be quantified by gating on viable cells under physiological conditions. In summary, with this novel method, receptor clustering on nonadherent cells can easily be monitored by high-throughput conventional flow cytometry.

Analysis of circulating plasmacytoid dendritic cells during the course of sepsis

BACKGROUND

Sepsis is characterized as a biphasic immune reaction in response to invading micro-organisms causing a life-threatening condition. This reaction is triggered by the activation of many different immune cells causing a dramatic inflammatory response often followed by immunosuppression. The balance of the immune response in this complex interplay of pro- and anti-inflammatory processes is crucial for the course of sepsis and host survival. For a better understanding of the involved mechanisms, a precise knowledge of participating immune cells in a timely manner is necessary.

METHODS

We analyzed circulating plasmacytoid dendritic cells (pDCs) by using multicolor, flow cytometric analysis in septic patients over 28 days. In addition, we assessed disease severity, organ failure, and outcome in these septic patients.

RESULTS

The numbers of circulating pDCs started to increase at day 1 after the onset of sepsis and were greatly increased from day 4 after sepsis onset. At days 7 and 14, the numbers of circulating pDCs peaked and returned to normal values at day 28 after the onset of sepsis. These changes were accompanied by increased expression of CD11b, which is known as crucial factor for transendothelial migration. In addition, the circulating pDCs in nonsurvivors showed greatly decreased values compared with survivors over the course of sepsis.

CONCLUSION

The results presented here support the concept that circulating pDCs might have an important role in the immune response during sepsis and might function as an early predictive biomarker for the outcome of sepsis.

Junctional adhesion molecule A promotes epithelial tight junction assembly to augment lung barrier function

Epithelial barrier function is maintained by tight junction proteins that control paracellular fluid flux. Among these proteins is junctional adhesion molecule A (JAM-A), an Ig fold transmembrane protein. To assess JAM-A function in the lung, we depleted JAM-A in primary alveolar epithelial cells using shRNA. In cultured cells, loss of JAM-A caused an approximately 30% decrease in transepithelial resistance, decreased expression of the tight junction scaffold protein zonula occludens 1, and disrupted junctional localization of the structural transmembrane protein claudin-18. Consistent with findings in other organs, loss of JAM-A decreased β1 integrin expression and impaired filamentous actin formation. Using a model of mild systemic endoxotemia induced by i.p. injection of lipopolysaccharide, we report that JAM-A(-/-) mice showed increased susceptibility to pulmonary edema. On injury, the enhanced susceptibility of JAM-A(-/-) mice to edema correlated with increased, transient disruption of claudin-18, zonula occludens 1, and zonula occludens 2 localization to lung tight junctions in situ along with a delay in up-regulation of claudin-4. In contrast, wild-type mice showed no change in lung tight junction morphologic features in response to mild systemic endotoxemia. These findings support a key role of JAM-A in promoting tight junction homeostasis and lung barrier function by coordinating interactions among claudins, the tight junction scaffold, and the cytoskeleton.

Defining the role of CD2 in disease progression and overall survival among patients with completely resected stage-II to -III cutaneous melanoma

BACKGROUND

Accurate assessment of prognosis remains clinically challenging in stage II to III cutaneous melanoma. Studies have implicated CD2 in immune surveillance, T-cell activation, and antitumor immunity, but its role in melanoma progression warrants further investigation.

OBJECTIVE

We sought to investigate the prognostic role of CD2 in primary cutaneous melanoma.

METHODS

Patients with American Joint Committee on Cancer stage II and III cutaneous melanoma were identified by retrospective review of dermatopathology databases from 2001 to 2010 at Mount Sinai Medical Center and Geisinger Medical Center. Additional patients were provided by New York University Medical Center based on retrospective review and tissue availability. Immunohistochemistry was performed on tumors from 90 patients with known recurrence status and documented follow-up.

RESULTS

Primary tumors from patients who developed recurrent disease had fewer CD2(+) cells (P = .0003). In multivariable analyses including standard clinicopathologic predictors, CD2 was an independent predictor of disease recurrence (P = .008) and overall survival (P = .007). CD2 count correlated with characterization of tumor-infiltrating lymphocytes (P = .0004). Among the intermediate prognosis group of patients with nonbrisk tumor-infiltrating lymphocytes, CD2 count was predictive of disease recurrence (P = .0006) and overall survival (P = .0318).

LIMITATIONS

Our retrospective design may have resulted in incomplete representation of patients lacking documented follow-up.

CONCLUSIONS

CD2 may be an independent predictor of disease recurrence and overall survival among patients with primary cutaneous melanoma.

Microbe-dependent CD11b+ IgA+ plasma cells mediate robust early-phase intestinal IgA responses in mice

Intestinal plasma cells predominantly produce immunoglobulin (Ig) A, however, their functional diversity remains poorly characterized. Here we show that murine intestinal IgA plasma cells can be newly classified into two populations on the basis of CD11b expression, which cannot be discriminated by currently known criteria such as general plasma cell markers, B cell origin and T cell dependence. CD11b⁺ IgA⁺ plasma cells require the lymphoid structure of Peyer’s patches, produce more IgA than CD11b⁻ IgA⁺ plasma cells, proliferate vigorously, and require microbial stimulation and IL-10 for their development and maintenance. These features allow CD11b⁺ IgA⁺ plasma cells to mediate early-phase antigen-specific intestinal IgA responses induced by oral immunization with protein antigen. These findings reveal the functional diversity of IgA⁺ plasma cells in the murine intestine.

Intestinal plasma cells contribute to the delicate balance between immunity against pathogens and tolerance of intestinal microflora. Kunisawa et al. identify a subpopulation of plasma cells whose proliferation depends on stimulation by microbes and IL-10, and which mediate early-phase responses to oral antigens.

Leukocytes regulate retinal capillary degeneration in the diabetic mouse via generation of leukotrienes

Understanding the early pathogenesis of DR may uncover new therapeutic targets to prevent or slow the progression of this sight-threatening disorder. We investigated the role of leukocyte-mediated generation of LTs in regulation of retinal capillary degeneration and inflammation in the diabetic mouse. We generated (1) chimeric mice that lacked the ability to generate LTs by transplanting 5LO-/- bone marrow cells into ND.WT mice and into SD.WT mice and (2) "control" chimeric mice by transplanting WT bone marrow cells into 5LO-/- mice or into WT mice. Retinas from diabetic chimeric mice with WT marrow demonstrated capillary degeneration to the same extent as retinas from diabetic, nonchimeric WT mice. In contrast, retinas from diabetic chimeric mice with 5LO-/- marrow developed significantly less capillary degeneration and pericyte loss (P<0.05). In the retinas from chimeric mice with WT marrow, diabetes induced a rise in leukocyte adherence to the microvasculature, expression of the NF-κB p65 subunit, and ICAM1, superoxide generation, and retinal microvascular permeability, yet these characteristic responses were blunted by >50% in diabetic chimeras containing 5LO-/- leukocytes (P<0.05). Our data suggest the critical involvement of leukocytes and LTs in the regulation of inflammation and capillary degeneration in DR.

PSGL-1/selectin and ICAM-1/CD18 interactions are involved in macrophage-induced drug resistance in myeloma

Chemoresistance is the major obstacle in multiple myeloma (MM) management. We previously showed that macrophages protect myeloma cells, on a cell contact basis, from melphalan or dexamethasone-induced apoptosis in vitro. In this study, we found that macrophage-mediated myeloma drug resistance was also seen with purified macrophages from myeloma patients' bone marrow (BM) in vitro and was confirmed in vivo using the human myeloma-SCID (severe combined immunodeficient) mouse model. By profiling differentially regulated and paired plasma membrane protein genes, we showed that PSGL-1 (P-selectin glycoprotein ligand-1)/selectins and ICAM-1/CD18 played an important role in macrophage-mediated myeloma cell drug resistance, as blocking antibodies against these molecules or genetic knockdown of PSGL-1 or ICAM-1 in myeloma cells repressed macrophages' ability to protect myeloma cells. Interaction of macrophages and myeloma cells via these molecules activated Src and Erk1/2 kinases and c-myc pathways and suppressed caspase activation induced by chemotherapy drugs. Thus, our study sheds new light on the mechanism of drug resistance in MM and provides novel targets for improving the efficacy of chemotherapy in patients.

[Natural killer cells and cancer. Regulation by the killer cell Ig-like receptors (KIR)]

自然杀伤（natural killer, NK）细胞是先天性免疫效应细胞，约占人外周血淋巴细胞总数的10%-15%，主要参与免疫监视，以消除转化细胞和病毒感染细胞。NK细胞最初被界定是由于它们具有自发消除少数主要组织相容性复合物Ⅰ类（major histocompatibility class Ⅰ, MHC-Ⅰ）自身分子表达缺乏细胞的能力，即常说的“丢失自我”识别能力。NK细胞表面表达的MHC-Ⅰ特异性抑制性受体，可使NK细胞对表达MHC-Ⅰ的正常细胞耐受，此为丢失自我识别能力的分子基础。由于缺乏抑制性受体的配体，表面MHC-Ⅰ表达下调的肿瘤细胞和病毒感染细胞易受NK细胞攻击。杀伤细胞免疫球蛋白样受体（KIR; CD158）组成MHC-Ⅰ结合受体家族，对调节人NK细胞和部分T细胞的活化阈值起重要作用。KIR多样性使NK细胞具有多种功能，在此我们将综述多个水平上的KIR多样性，并诠释KIR多样性是如何影响各种疾病（包括癌症）的易感性的。我们将进一步阐述通过针对KIR进行癌症治疗的策略：利用KIR/MHC-Ⅰ配体的错配以强化造血干细胞移植的效果，以及通过阻滞KIR以增强对肿瘤细胞的杀伤力。

Osteoblast retraction induced by adherent neutrophils promotes osteoclast bone resorption: implication for altered bone remodeling in chronic gout

Bone destruction in chronic gout is correlated with deposits of monosodium urate (MSU) crystals. Bone with MSU tophi were histopathologically shown to have altered remodeling and cellular distribution. We investigated the impact of neutrophils in bone remodeling associated with MSU and demonstrated that neutrophils, through elastase localized at their surface, induced retraction of confluent osteoblasts (OBs) previously layered on calcified matrix. This OB retraction allowed osteoclasts to resorb cell-free areas of the matrix. This neutrophil effect was concentration dependent and time dependent and required direct contact with OBs. Exposure of OBs to MSU greatly promoted neutrophil adherence to OBs. Neutrophil membrane at the contact zone with OBs showed concentrated fluorescence of dye PKH-67, indicating a cellular contact. Neutrophil-OB interaction increased the survival of neutrophils, reduced their release of lactoferrin in presence of MSU and did not change OB-mediated mineralization. The adhesion of neutrophils to OBs was heterotypic through neutrophil CD29/CD49d and OB-fibronectin peptide CS1. Leukotriene B₄ (LTB₄) and platelet-activating factor (PAF) were also involved in neutrophil adherence to OBs, as shown by the blocking effect of selective LTB₄ and PAF receptor antagonists, and a cytosolic phospholipase A(2α) (cPLA(2α)) inhibitor. Blockade of CD49d/CS1 and inhibition of the cPLA(2α) had subadditive effects, reducing by 60% the adherence of neutrophils to OBs. Taken together, these data showed that neutrophil adhesion to MSU-activated OBs was mediated by the β₁ integrin CD29/CD49d-fibronectin peptide CS1 receptors and cPLA(2α)-derived metabolites and impacts on OB and osteoclast functions. These interactions could be involved in the local bone remodeling process of gout.

In vitro manipulation of endothelial progenitor cell adhesion to vascular endothelium and extracellular matrix by the phorbol ester PMA

Injection of endothelial progenitor cells (EPCs) into arteries for cell therapy is a promising field in regenerative medicine. However, adhesion of EPCs during capillary passage is restricted, and non-adhering cells are lost into circulation. Here we demonstrate that it is possible to achieve a three- to sevenfold higher rate of EPC adhesion to endothelium and extracellular matrix molecules after short-term activation with phorbol myristate acetate (PMA). In addition, differentiation and toxicity analyses of PMA activated EPCs showed no impact on cell differentiation and negligible impact on cell survival.

NF-κ B-dependent upregulation of ICAM-1 by HPV16-E6/E7 facilitates NK cell/target cell interaction

NK cell recognition of tumor cells is mediated by a delicate balance of signals received by MHC class I-binding inhibitory NK cell receptors and activating NK cell receptors, which mainly bind to virus-, stress- or tumor-induced ligands. In addition, adhesion molecules such as the intercellular adhesion molecule-1 (ICAM-1) and its receptors, the lymphocyte function-associated antigen-1 (LFA-1) and Mac-1, are crucial for immune synapse formation and NK cell-mediated killing. In this study, we show that expression of the adhesion molecule ICAM-1 was rapidly induced by E6 and -E7 oncoproteins of HPV16, -18, -5 and -8, but not of HPV38 and -6 in primary human keratinocytes after retroviral transduction. ICAM-1 was upregulated in E6E7-expressing keratinocytes both at mRNA and protein levels. The observed ICAM-1 upregulation in HPV16-E6E7-expressing keratinocytes was partially dependent on activation of the NF-κB pathway. Importantly, the upregulated ICAM-1 expression in HPV16-E6E7-expressing keratinocytes led to enhanced conjugate formation with NK cells. We previously showed that HPV16-positive cervical carcinomas frequently express low levels of inhibitory NK cell ligands and high levels of activating NK cell ligands. Moreover, levels of the adhesion molecule ICAM-1 are enhanced by HPV16-E6/E7. Therefore, strategies that aim at harnessing NK cells might be beneficial for the treatment of cervical carcinoma.

Natural killer cells and cancer: regulation by the killer cell Ig-like receptors (KIR)

Natural killer (NK) cells are innate immune effector cells that make up approximately 10-15% of the peripheral blood lymphocytes in humans and are primarily involved in immunosurveillance to eliminate transformed and virally-infected cells. They were originally defined by their ability to spontaneously eliminate rare cells lacking expression of class I major histocompatibility complex (MHC-I) self molecules, which is commonly referred to as "missing self" recognition. The molecular basis for missing self recognition emerges from the expression of MHC-I-specific inhibitory receptors on the NK cell surface that tolerize NK cells toward normal MHC-I-expressing cells. By lacking inhibitory receptor ligands, tumor cells or virus-infected cells that have down-modulated surface MHC-I expression become susceptible to attack by NK cells. Killer cell Ig-like receptors (KIR; CD158) constitute a family of MHC-I binding receptors that plays a major role in regulating the activation thresholds of NK cells and some T cells in humans. Here, we review the multiple levels of KIR diversity that contribute to the generation of a highly varied NK cell repertoire and explain how this diversity can influence susceptibility to a variety of diseases, including cancer. We further describe strategies by which KIR can be manipulated therapeutically to treat cancer, through the exploitation of KIR/MHC-I ligand mismatch to potentiate hematopoietic stem cell transplantation and the use of KIR blockade to enhance tumor cell killing.

Adhesion and transcellular migration of neutrophils and B lymphocytes on fibroblasts

During tissue inflammation, infiltrated leukocytes may have physical contacts with fibroblasts. We observed that neutrophils and B lymphocytes adhered in a larger proportion than T cells on cultured fibroblasts. Microscopy showed that adhesion was also characterized by leukocyte engulfment by the fibroblasts. In migration assays, only neutrophils and B lymphocytes were selectively able to migrate through a fibroblast barrier. Adhesion and migration were increased by stimulation with tumor necrosis factor-alpha (TNF-alpha) and phorbol-12-myristate-13-acetate (PMA). Antibodies against ICAM-1/beta2 integrin blocked the interaction of neutrophils to fibroblasts. For B lymphocytes the couple VCAM-1/alpha4 integrin was also involved in this interaction. Human skin fibroblasts presented similar adhesion characteristics as rat cardiac fibroblasts. By measuring the distance between the border of migration holes and cadherin-positive adherens junctions, more than 65% of the holes correspond to the transcellular route over the paracellular route. Furthermore, vimentin staining revealed that the migration holes were highly nested by intermediate filaments in accordance with the transcellular route. Our results demonstrated that engulfment of neutrophils and B lymphocytes by fibroblasts resulted in selective passage by a transcellular route.

Analysis of adhesion molecules, target cells, and role of IL-2 in human FOXP3+ regulatory T cell suppressor function

FOXP3(+) regulatory T cells (Tregs) are central to the maintenance of self-tolerance and immune homeostasis. The mechanisms of action and cellular targets for Treg-mediated suppression remain controversial. The critical adhesion molecules utilized by Tregs for the interaction with their target cells have not been well characterized. We show that human CD4(+)FOXP3(+)CD25(high) cells (hTregs) suppress the activation of mouse responders as efficiently as mouse Tregs. LFA-1 (CD11a/CD18) on the hTregs is critical for their suppressor function, since suppression can be reversed with blocking anti-hCD11a or anti-hCD18 mAb. Tregs from patients with LFA-1 deficiency fail to suppress human and mouse responders. Mouse CD4(+) T cells deficient in ICAM-1 can be suppressed by hTregs, indicating that the hTregs target mouse dendritic cells (DCs) through the binding of human LFA-1 to mouse ICAM-1. Coculture of mouse DCs with hTregs, but not hTregs from LFA-1-deficient patients, prevented the up-regulation of CD80/CD86 on the DCs and their capacity to activate responder T cells. Lastly, IL-2 is not required for hTreg suppressor function under optimal stimulatory condition and IL-2 consumption plays no role in hTreg-mediated suppression. Taken together, one of the mechanisms of Treg-mediated suppression functions across species and mediates an LFA-1/ICAM-1-dependent interaction between Tregs and DCs.

Revised model for early memory T-cell protection against respiratory virus challenge

Evaluation of: Kohlmeier JE, Miller SC, Smith J et al.: The chemokine receptor CCR5 plays a key role in the early memory CD8+ T cell response to respiratory virus infections. Immunity 29(1), 101–113 (2008). Following primary respiratory virus infection, a portion of memory T cells remain in the lung to serve to limit virus replication. However, the systemic population of these memory T cells gradually converts from effector memory T cells to central memory T cells, resulting in a gradual loss of the memory T-cell population in the lung airways, a feature that coincides with decline of the early recall response to virus infection. Kohlmeier and colleagues have identified a crucial role for the C-C chemokine receptor (CCR5) in the accelerated recruitment of memory CD8+ T cells in the lungs of virally infected mice. Their findings redefine the current model for early memory T-cell protection against respiratory virus challenge, and are important for rationale design of cell-mediated vaccines.

Intestinal epithelial CD98: an oligomeric and multifunctional protein

The intestinal epithelial cell-surface molecule, CD98 is a type II membrane glycoprotein. Molecular orientation studies have demonstrated that the C-terminal tail of human CD98 (hCD98), which contains a PDZ-binding domain, is extracellular. In intestinal epithelial cells, CD98 is covalently linked to an amino-acid transporter with which it forms a heterodimer. This heterodimer associates with beta(1)-integrin and intercellular adhesion molecular 1 (ICAM-1) to form a macromolecular complex in the basolateral membranes of polarized intestinal epithelial cells. This review focuses on the multifunctional roles of CD98, including involvement in extracellular signaling, adhesion/polarity, and amino-acid transporter expression in intestinal epithelia. A role for CD98 in intestinal inflammation, such as Intestinal Bowel Disease (IBD), is also proposed.

CB2 cannabinoid receptor agonist JWH-015 modulates human monocyte migration through defined intracellular signaling pathways

Recruitment of leukocytes to inflammatory sites is crucial in the pathogenesis of chronic inflammatory diseases. The aim of this study was to investigate if activation of CB2 cannabinoid receptors would modulate the chemotactic response of human monocytes. Human monocytes treated with the CB2 agonist JWH-015 for 12-18 h showed significantly reduced migration to chemokines CCL2 and CCL3, associated with reduced mRNA and surface expression of their receptors CCR2 and CCR1. The induction of ICAM-1 in response to IFN-gamma was inhibited by JWH-015. Moreover, JWH-015 cross-desensitized human monocytes for migration in response to CCL2 and CCL3 by its own chemoattractant properties. The CB2-selective antagonist SR-144528, but not the CB1 antagonist SR-147778, reversed JWH-015-induced actions, whereas the CB2 agonist JWH-133 mimicked the effects of JWH-015. The investigation of underlying pathways revealed the involvement of phosphatidylinositol 3-kinase/Akt and ERK1/2 but not p38 MAPK. In conclusion, selective activation of CB2 receptors modulates chemotaxis of human monocytes, which might have crucial effects in chronic inflammatory disorders such as atherosclerosis or rheumatoid arthritis.

The contribution of associated congenital anomalies in understanding Hirschsprung's disease

Hirschsprung's disease (HSCR) is a complex congenital disorder which, from a molecular perspective, appears to result due to disruption of normal signalling during development of enteric nerve cells, resulting in aganglionosis of the distal bowel. Associated congenital anomalies occur in at least 5-32% (mean 21%) of patients and certain syndromic phenotypes have been linked to distinct genetic sites, indicating underlying genetic associations of the disease and probable gene-gene interaction in its pathogenesis. Clear-cut associations with HSCR include Down's syndrome, dominant sensorineural deafness, Waardenburg syndrome, neurofibromatosis, neuroblastoma, phaeochromocytoma, the MEN type IIB syndrome and other abnormalities. Individual anomalies vary from 2.97% to 8%, the most frequent being the gastrointestinal tract (GIT) (8.05%), the central nervous system (CNS) and sensorineural anomalies (6.79%) and the genito-urinary tract (6.05%). Other associated systems include the musculoskeletal (5.12%), cardiovascular systems (4.99%), craniofacial and eye abnormalities (3%) and less frequently the skin and integumentary system (ectodermal dysplasia) and syndromes related to cholesterol and fat metabolism. In addition to associations with neuroblastoma and tumours related to MEN2B, HSCR may also be associated with tumours of neural origin such as ganglioneuroma, ganglioneuroblastoma, retinoblastoma and tumours associated with neurofibromatosis and other autonomic nervous system disturbances. The contribution of the major susceptibility genes on chromosome 10 (RET) and chromosome 13 (EDNRB) is well established in the phenotypic expression of HSCR. Whereas major RET mutations may result in HSCR by haploinsufficiency in 20-25% of cases, the etiology of the majority of sporadic HSCR is not as clear, appearing to arise from the combined cumulative effects of susceptibility loci at critical genes controlling the mechanisms of cell proliferation, differentiation and maturation. In addition, potential "modifying" associations exist with chromosome 2, 9, 20, 21 and 22, and we explore the importance of certain flanking genes of critical areas in the final phenotypic expression of HSCR.

Cooperative Disengagement of Fas and Intercellular Adhesion Molecule-1 Function in Neoplastic Cells Confers Enhanced Colonization Efficiency

Understanding the mechanisms of tumor progression is crucial toward the development of therapeutic interventions. Although the loss of sensitivity to cell death is a hallmark of neoplastic progression, it is likely one of several essential features that underlie a malignantly proficient or aggressive tumorigenic phenotype. Here, we identified intercellular adhesion molecule-1 (ICAM-1) as a molecule with expression coordinately regulated with Fas and inversely correlated with malignant phenotype between matched pairs of differentially aggressive malignant subpopulations in three mouse models. To determine whether coordinate expression of Fas and ICAM-1 regulated malignant behavior, tumor sublines were produced that expressed either lower levels of both Fas and ICAM-1, lower levels of Fas, or lower levels of ICAM-1 and then assessed for metastatic lung tumor growth. Tumor sublines rendered both Fas incompetent and ICAM-1 incompetent displayed significantly higher numbers of tumor nodules compared with tumor sublines separately expressing low levels of Fas or ICAM-1. However, all tumor sublines regardless of their Fas and ICAM-1 levels comparably infiltrated the lung, suggesting that Fas- and ICAM-1–based interactions ultimately influenced lung colonization efficiency. Overall, these data suggested that both Fas and ICAM-1 pathways cooperated to regulate tumor progression and that the coordinate down-regulation of Fas and ICAM-1 intensified malignant progression at the level of colonization. Thus, a FasloICAM-1lo phenotype may be characteristic of at least certain advancing, immune-resistant neoplastic subpopulations.

Anatomy of a murder—signal transduction pathways leading to activation of natural killer cells

Natural killer (NK) cells control the early phases of viral infections, modulate antigen-specific immune responses, and participate in the rejection of tumours and bone marrow grafts. A fine balance between inhibitory and activating receptors tightly regulates NK cell activation. Biochemical studies in human cell lines and primary cells have revealed some of the activating NK cell signalling pathways, however animal models are instrumental to understand the physiological implications of these findings for immune responses in vivo. Gene targeting in mice and biochemical studies in cells are helping to dissect out the various signal transduction pathways that control NK cell activation. A clearer view of these pathways may eventually help designing more effective immune therapies based on the use of NK cells.

Anoxia and reoxygenation of human endothelial cells decrease ceramide glucosyltransferase expression and activates caspases

Endothelial oxidative stress induces cellular activation and sometimes death. Endothelial death can occur via necrosis or apoptosis. Understanding the mechanisms involved in cellular activation and death may lead to therapeutics designed to increase death or preserve cellular function. In the present study, brief periods of anoxia (3 h) followed by varying lengths of reoxygenation (0-5 h) lead to a time-dependent increase in human umbilical vein endothelial cell (HUVEC) caspase activity. Furthermore, ROCK-1 cleavage, which is dependent on caspase-3 activity, was also increased in cells undergoing oxidative stress compared with normoxic cells. Microarray data demonstrated that glucosylceramide synthase (GCS; glucosylceramide transferase), but not acid sphingomyelinase, was modulated by anoxia and reoxygenation. We confirmed that GCS mRNA and protein expression were significantly decreased in a time-dependent fashion following oxidative stress by real-time polymerase chain reaction and Western blot, respectively. Treatment of normoxic cells with the GCS-specific inhibitor, D,L-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP), increased caspase activity to the same degree as cells undergoing oxidative stress. Fumonisin B1, the N-acyl-sphinganine dehydrogenase (e.g., ceramide synthase) inhibitor significantly attenuated caspase activity in HUVECs undergoing oxidative stress. These data suggest that alterations in GCS expression following brief periods of oxidative stress in human endothelial cells lead to increased caspase activity.

A very late activating antigen-alpha4 (CD49d) monoclonal antibody, BU49 induces phosphorylation of a cAMP response element-binding protein (CREB), resulting in induction of homotypic cell aggregation and enhancement of interleukin-8 (IL-8) production

A very late activating antigen-alpha4 (CD49d) monoclonal antibody (mAb), BU49 was found to induce phosphorylation of a cAMP response element-binding protein (CREB) in the human monocyte-like cell line, U937. This phosphorylation of CREB was completely inhibited by a protein kinase A (PKA) inhibitor H-89 with the optimum concentration (completely inhibits PKA). Furthermore, BU49 strongly and rapidly (within 5 hr) induced homotypic cell aggregation in the U937 cells accompanied by CREB phosphorylation. This cell aggregation was also completely inhibited by the addition of H-89. Interestingly, both of two mAbs (mAb13 and 4B4) recognizing different epitopes on the CD29 (beta1 integrin) completely inhibited this aggregation at the late phase (18 to 24 hr) but not at the early phase (5 hr) after cultured with BU49. On the other hand, BU49 significantly enhanced interleukin-8 (IL-8) production from the U937 cells into the culture supernatant. In addition, this IL-8 production was significantly blocked in the presence of H-89 with the optimum concentration. However, a CD29 mAb which inhibits homotypic cell aggregation could not block this IL-8 production. Taken together, these findings indicate that BU49 induces CREB phosphorylation mainly mediated by PKA, which finally results in the induction of homotypic cell aggregation and the enhancement of IL-8 production. Furthermore, these findings also indicate that the enhancement of IL-8 production from the U937 cells induced by BU49 partially depends on CREB phosphorylation mainly mediated by PKA.

Amplification of extracellular nucleotide-induced leukocyte(s) degranulation by contingent autocrine and paracrine mode of leukotriene-mediated chemokine receptor activation

Extracellular nucleotide-induced stimulation and activation of peripheral blood leukocytes and subsequent degranulation play a critical role in immediate-type hypersensitivity reaction and other inflammatory diseases. The extracellular nucleotides stimulate a P2Y receptor(s) on human PMN with the pharmacological profile similar to that of the P2Y2 receptor. Upon activation of P2Y2, arachidonic acid, formed from the membrane bound lipids by phospholipase A2, which subsequently metabolized by 5-lipoxygenase to form the leukotrienes. Of the several leukotrienes generated, LTB(4) is a potent pro-inflammatory chemokine. Upon its release LTB(4) binds to the PMN in a paracrine manner and also other leukocytes such as monocytes at the site of vascular injury, leading to an accelerated rate of degranulation. It is known that LTA(4) formed in the 5-lipoxygenase pathway in PMN could be released from PMN by receptor-mediated transport. Upon its release, the monocytes, erythrocytes, platelet, endothelial or smooth muscle cells can take up LTA(4). The endogenous LTA(4) hydrolase form the LTB(4) from LTA(4) in erythrocytes, platelet, endothelial or smooth muscle cells. As in PMN, LTB(4) is released from these cells via receptor-mediated transport to the extracellular milieu. Thus, released LTB(4) most likely acts as potentially accelerating factor in PMN and MN degranulation through its receptor-specific binding. It is not known whether any LTB(4) receptor exists in cytoplasm in any given cell type and also, the existence of any other signaling cascade for the extracellular nucleotide-induced leukocyte degranulation. Thus, it is convincing that the extracellular nucleotides released from the activated platelets and other damaged cell types exacerbate the inflammatory response by leukotriene generation. In turn the leukotriene will act in both autocrine and paracrine manner to amplify the degranulation processes in leukocytes invoked by extracellular nucleotides.

Primary Research: Short Communication: Evidence Supporting Rare AIDS-Kaposi's Sarcoma Metastasis In Keeping With Their Vascular Endothelial Evolution

BACKGROUND: It is postulated that the unusual manifestations of Kaposis's sarcoma cells in nonendothelial brain tissues and on eyeballs in advanced acquired immune deficiency syndrome (AIDS) cases are metastasized AIDS-Kaposi's sarcoma cells arising from vascular endothelial cells. METHODS: Experiments were performed to explore the above hypothesis by testing for intercellular adhesion molecule-1 (CD54 antigens) on cutaneous AIDS-Kaposi's sarcoma cells as well as on AIDS-Kaposi's sarcoma cells isolated from eyeballs as studies have illustrated that, unlike localized Kaposi's sarcoma cells of primary lesions, proliferating Kaposi's sarcoma cells in proximity to primary lesions express a negative or diminished phenotype when evaluated for identical surface antigens. Parallel CD54 antigen tests were done on vascular endothelial cells and monocytes/macrophages as endothelial cells are considered evolutionarily related to Kaposi's sarcoma cells and monocytes/macrophages are ideal CD54 antigen positive controls. RESULTS: Our data showed that only AIDS-Kaposi's sarcoma cells of the eyes did not express CD54 antigens. CONCLUSIONS: We therefore report that our findings support the postulation suggesting AIDS-Kaposi's sarcoma dissemination in advanced AIDS patients in keeping with their vascular endothelial heredity.

Molecular, cellular and functional characterizations of a novel ICAM-like molecule of the immunoglobulin superfamily from Leishmania mexicana amazonensis

A molecule with two immunoglobulin (Ig) domains cloned from Leishmania mexicana amazonensis was characterized to have a sequence homology to the Ig domains of an ICAM-like molecule telencephalin, cloned from the brain of mammals, as well as to the variable domains of human immunoglobulin lambda light chain. The molecule therefore appears to be an ICAM-like molecule as well as a member of the immunoglobulin superfamily. We thus named it ICAM-L for Leishmania ICAM. The gene was coamplified with the ribonucleotide reductase M(2) subunit gene responsible for hydroxyurea resistance from hydroxyurea (Hu)-resistant Leishmania variants. As expected, an increase of the ICAM-L protein as well as an increase of the specific ICAM-L transcript of 2.1 kb was detected in the Hu-resistant variants with increasing doses of the drug used for resistance selection. Structurally, ICAM-L is more similar to the secretory adhesive molecules, such as 1Bgp and the link protein of the immunoglobulin superfamily, in that it lacks a transmembrane region and a GPI anchor sequence. Although ICAM-L was mainly localized in the nucleus of the parasite by confocal microscopy, however, detailed studies by electron microscopy and FACS analysis indicated that the protein was also localized on the surface of the parasite. The surface localization of the protein was furthered strengthened by the observations that anti-ICAM-L or ICAM-L itself can significantly block the binding of the parasite to macrophages. The blocking of the attachment of parasite to macrophages may indicate that ICAM-L functions as an intercellular adhesive molecule.

Monocytic cells synthesize, adhere to, and migrate on laminin-8 (alpha 4 beta 1 gamma 1)

Laminins, a growing family of large heterotrimeric proteins with cell adhesive and signaling properties, are major components of vascular and other basement membranes. Expression, recognition, and use of laminin isoforms by leukocytes are poorly understood. In monoblastic THP-1 cells, transcripts for laminin gamma(1)-, beta(1)-, and alpha(4)-chains were detected by RT-PCR. Following immunoaffinity purification on a laminin beta(1) Ab-Sepharose column, laminin beta(1)- (220 kDa), gamma(1)- (200 kDa), and alpha(4)- (180/200 kDa) chains were detected by Western blotting in THP-1 cells and in two other monoblastic cell lines, U-937 and Mono Mac 6. After cell permeabilization, a mAb to laminin gamma(1)-chain reacted with practically all blood monocytes by immunofluorescence flow cytometry, and laminin-8 (alpha(4)beta(1)gamma(1)) could be isolated also from these cells. Monoblastic JOSK-I cells adhered constitutively to immobilized recombinant laminin-8, less than to laminin-10/11 (alpha(5)beta(1)gamma(1)/alpha(5)beta(2)gamma(1)) but to a higher level than to laminin-1 (alpha(1)beta(1)gamma(1)). Compared with the other laminin isoforms, adhesion to laminin-8 was preferentially mediated by alpha(6)beta(1) and beta(2) integrins. Laminin-8 and, to a lower extent, laminin-1 promoted spontaneous and chemokine-induced migration of blood monocytes, whereas laminin-10/11 was inhibitory. Altogether, the results indicate that leukocytes, as other cell types, are able to synthesize complete laminin molecules. Expression, recognition, and use of laminin-8 by leukocytes suggest a major role of this laminin isoform in leukocyte physiology.

Molecular and functional characterization of porcine LFA-1 using monoclonal antibodies to CD11a and CD18

We describe in this report the production and characterization of monoclonal antibodies (mAb) to the swine homologues of CD11a and CD18 antigens, and their use for phenotypic and functional analysis of porcine leukocytes. Monoclonal antibodies BL1H8 and BL2F1 precipitated two bands of approximately 170 and 95 kDa, whereas mAb BA3H2 brought down three bands of 170, 155 and 95 kDa, from alveolar macrophage lysates. Clearance of macrophage lysates with mAbs BL1H8 and BL2F1 resulted in complete removal of the 170-kDa band. The cell distribution of the molecules recognized by these mAbs was similar to that of human LFA-1. It was found on all leukocytes, although its expression varied among the different leukocyte subpopulations, with monocytes, granulocytes and a subset of CD8+ cells expressing the highest levels. Cross-blocking studies showed that these antibodies recognize different epitopes on porcine LFA-1. Both anti-LFA-1 mAbs strongly inhibited the mitogenic response of PBMC to ConA, whereas the anti-CD18 mAb had no effect. These anti-LFA-1 mAbs also inhibited the mixed lymphocyte reaction (MLR) and the NK cell-mediated lysis of K-562 cells.

Inhibition of natural killer cell-mediated cytotoxicity by Kaposi's sarcoma-associated herpesvirus K5 protein

Kaposi's sarcoma-associated herpesvirus (KSHV) K3 and K5 proteins dramatically downregulate MHC class I molecules. However, although MHC class I downregulation may protect KSHV-infected cells from cytotoxic T lymphocyte recognition, these cells become potential targets for natural killer (NK) cell-mediated lysis. We now show that K5 also downregulates ICAM-1 and B7-2, which are ligands for NK cell-mediated cytotoxicity receptors. As a consequence, K5 expression drastically inhibits NK cell-mediated cytotoxicity. Conversely, de novo expression of B7-2 and ICAM-1 resensitizes the K5-expressing cells to NK cell-mediated cytotoxicity. This is a novel viral immune evasion strategy where KSHV K5 achieves immune avoidance by downregulation of cellular ligands for NK cell-mediated cytotoxicity receptors.

Expression and functional activity of the very late activation antigen-4 molecule on human natural killer cells in different states of activation

In the present study we describe the expression and functional activity of the alpha4beta1 heterodimer molecule on human natural killer (NK) cells. Flow cytometric analyses showed that fresh and activated NK cells expressed high levels of very late activation antigen-4 (VLA-4) molecules. These cells bound to fibronectin (FN) and to its 38 000-MW proteolytic fragment through the VLA-4 integrin that was blocked with HP2/1 anti-alpha4 monoclonal antibodies (mAbs) and with the FN peptide fragment CS1. No inhibitory effects were observed in the presence of anti-alpha5 mAb, FN peptide fragment CS2 or other irrelevant mAb. Fresh NK cells were unable to aggregate, despite their expression of VLA-4, and only activated (cultured and lymphocyte-activated killer cells) NK cells showed homotypic aggregation with HP1/7 and HP2/4 anti-alpha4 mAb related to cellular activation. These results underline new evidence of how NK cells in different states of activation maintain different constitutive levels of alpha4beta1 integrin activity, and highlight the possibility of a different functional regulation by the cells bearing VLA-4, in the expression of these epitopes and their ability to interact with their ligands.

Impaired monocyte CD11b expression in interstitial inflammation in hemodialysis patients

BACKGROUND

It is not known to what extent intravascular phenotypic alterations in adhesion molecule expression induced by hemodialysis influence the recruitment of monocytes and their ability to up-regulate CD11b at the local site of inflammation in the interstitium. Using a skin suction chamber technique, we addressed these issues in eight hemodialysis patients and in eight healthy subjects.

METHODS

Two skin blisters were raised on the forearm of each individual and blister exudate collected. The blisters were then stimulated with autologous serum (active blister, intense inflammation) or buffer (control blister, intermediate inflammation), respectively. Thereafter the patients were treated with Cuprophan hemodialysis for four hours. After 10 hours, the exudate was aspirated from each chamber in all subjects. Monocyte count and expression of CD11b were analyzed in serum and blister fluid by flow cytometry. Then, monocytes from healthy blood donors were incubated in blister fluid from patients and healthy subjects in order to determine the local chemotactic activity in terms of CD11b up-regulation. Monocyte chemotactic protein-1 (MCP-1), a marker of systemic monocyte chemotactic activity, was also analyzed in serum at 0 and 10 hours in all individuals.

RESULTS

The number of monocytes at the site of inflammation in the interstitium in hemodialysis patients correlated with the expression of CD11b on transmigrated cells (r = 0.78, P < 0.001). Monocytes collected in the active blister fluid of dialysis patients expressed equal levels of CD11b as cells collected from healthy subjects. By contrast, monocytes collected from the control blisters of patients expressed lower levels of CD11b than cells from healthy subjects (P < 0.01), despite equal interstitial biological activity of CD11b-mobilizing factors in blister fluid from patients and healthy subjects and the fact that patients had higher systemic chemotactic activity in terms of MCP-1 concentration in serum (P < 0.001).

CONCLUSION

Monocytes from hemodialysis patients have the capacity to mobilize CD11b to the same extent as cells from healthy individuals at the inflammatory spot, but more intense stimuli are required for such actions, probably because of a transient refractoriness.

Leukocyte integrin-dependent and antibody-independent cytotoxicity of macrophage against allografts

Macrophages (Mphis), but not T cells, infiltrating into the rejection site of either i.p. allografted Meth A (H-2d) fibrosarcoma cells in C57BL/6 (B6) (H-2b) mice or BALB/c (H-2d) skin onto B6 mice are cytotoxic against allografts with H-2d specificity. To determine the mechanisms of specific killing of allografts by allograft-induced Mphi (AIM), we raised approximately 5,000 rat monoclonal antibodies (mAbs) against AIM and selected three of them (R1-73, R2-40 and R1-34), each of which inhibited cytotoxic activity against allografts in a dose-dependent manner. The antigens recognized by R1-73, R2-40 and R1-34 mAbs were defined by immunoprecipitation and Western blot analyses as CD11a, CD18 and CD11b, respectively; and the allografts expressed CD54, a ligand of CD11a or CD11b, suggesting leukocyte integrin-dependent killing. Although Ab-dependent cellular cytotoxicity has been recognized as a mechanism of specific killing by Mphis, the infiltration of AIM into the rejection site of allografts far (approximately 6 days) preceded the appearance of serum IgG Ab specific for the allograft. AIM exhibiting full cytotoxic activity against allografts was also induced in the transplantation site of Fcgamma receptor knockout [(B6x129) F1] mice as well as B10.D2 (H-2 compatible with allograft) and B6-xid (X-linked immunodeficiency with B cell-specific defect) strains of mice. In the latter two strains of mice, the levels of serum IgG Ab to the allograft were negligible. Moreover, the cytotoxic activity of AIM against allografts was not affected by pretreatment of the cells with anti-mouse IgG serum, suggesting Ab-independent cytotoxicity.

An acidic microenvironment impairs the generation of non-major histocompatibility complex-restricted killer cells

The microenvironment within solid tumours has often been shown to exhibit an acidic local pH. In recent studies we could demonstrate that an acidic extracellular pH (pHe) inhibits the non-major histocompatibility complex (MHC) -restricted cytotoxicity of immunocompetent effector cells. However, within tumours the activation of cytotoxic cells may already be impaired by low pHe. Therefore, we investigated the influence of acidic conditions on the generation of active killer cells. The cytotoxic activity of natural killer (NK) as well as lymphokine-activated killer (LAK) cells against K562, Daudi and Raji cells was analysed after an activation period of 3 days at pHe 7.2-6.5. A minor reduction of pHe from 7.2 to 7.0 during the culture period resulted in a strong inhibition of the natural cytotoxicity of NK cells. Furthermore, acidic pHe below 7.2 prevented the generation of activated LAK cells by interleukin-2 (IL-2). The cytotoxic capacity could not be reconstituted if cells cultured at a pHe of 6.5 were returned to physiological pH for another 24 hr. Analysis of the cellular subtypes within the various cultures did not reveal differences regarding the frequencies of NK cells, CD8+ T cells, or CD4+ T cells. However, an acidic pHe clearly inhibited the activation-induced increase of relevant adhesion molecules. The production of cytokines which are involved in the regulation of the cytotoxic process (tumour necrosis factor-alpha, interferon-gamma, IL-10, IL-12 and transforming growth factor-beta1) was also affected by pHe, as their release was strongly inhibited at pHe 7.0. Furthermore, we observed a considerable decrease in the metabolic activity of effector cells at acidic pHe. In summary, our findings suggest that an acidic microenvironment impairs the induction of an anti-tumoral immune response within solid tumours.

Reduced basal and stimulated leukocyte adherence in tumor endothelium of experimental pancreatic cancer

BACKGROUND

The interaction between immunocompetent cells and tumor endothelium is essential for an effective immunological response. In the present study, we evaluated resting and CD11b/CD18-mediated leukocyte adhesion in tumor vessels of experimental pancreatic cancer and in healthy pancreatic venules in the rat.

METHODS

Solid tumor fragments (1 mm3) were interposed intrapancreatically between inert transparent polymethylmetacrylate plates for intravital microscopy (n = 12) by which tumor microcirculation, leukocyte-tumor-endothelium interaction, and the effect of the chemoattractants N-formyl-methioninleucylphenylalanine (fMLP) and platelet-activating factor (PAF) on leukocyte adherence was investigated.

RESULTS

Leukocyte adhesion in pancreatic tumor vessels was significantly reduced compared to healthy pancreatic venules. Both fMLP and PAF dramatically increased leukocyte adherence in normal pancreatic venules. No change in leukocyte adhesion was present in tumor vessels after exposure to these chemotactic substances.

CONCLUSION

Resting and stimulated integrin-dependent leukocyte adhesion is strongly reduced in malignant vessels of experimental pancreatic cancer, which may be an important mechanism to escape immune control.

Involvement of LFA-1 in hepatic NK cell (pit cell)-mediated cytolysis and apoptosis of colon carcinoma cells

BACKGROUND/AIMS

Previous studies have shown that hepatic natural killer (NK) cells, also called pit cells, have a higher cytotoxicity against certain tumor cells and have a higher expression of the cell adhesion molecule CD11a as compared with blood NK cells. We further investigated the involvement of the adhesion molecules, reported to be involved in target cell killing by blood NK cells, in pit cell-mediated colon carcinoma cell killing.

METHODS

51Cr-release and DNA fragmentation were used to quantify target cell lysis and apoptosis, respectively. Adhesion of pit cells to CC531s monolayers was quantitated.

RESULTS

Flow cytometric analysis showed that pit cells expressed CD2, CD11a, CD18 and CD54. CC531s cells expressed only CD54. Treatment of freshly isolated pit cells with monoclonal antibodies (mAbs) to CD11a and CD18 inhibited not only the pit cell-mediated CC531s cytolysis but also the pit cell-induced apoptosis of CC531s cells. The combination of mAbs to CD11a, CD18 and CD54 further increased the inhibition of pit cell-mediated CC531s cytolysis and apoptosis. Anti-CD2 mAb did not affect these processes. The binding of pit cells to CC531s cells was also inhibited by anti-CD11a, and CD18 mAbs, but not by anti-CD2 mAb. Anti-CD54 mAb reduced the target cell killing and the binding only slightly.

CONCLUSIONS

These results indicate that CD11a/CD18 (LFA-1) present on pit cells plays an important role in pit cell-mediated target cell adhesion, lysis and apoptosis. This finding might explain why pit cells, which have a higher expression of LFA-1 as compared to blood NK cells, are more cytotoxic against tumor cells as compared to blood NK cells.

Inhibition of Cell Adhesion by Antibodies to Arg-Gly-Asp (RGD) in Normal Immunoglobulin for Therapeutic Use (Intravenous Immunoglobulin, IVIg)

Intravenous immunoglobulin (IVIg) therapy is associated with a broad range of immunomodulatory activities. Several of the postulated mechanisms of IVIg action relate to the presence of antibodies to molecules relevant for regulation of the immune response. This article reports that IVIg contains antibodies to the Arg-Gly-Asp (RGD) sequence, and the attachment site of a number of adhesive extracellular matrix proteins, including ligands for β1, β3, and β5 integrins. Anti-RGD antibodies were identified in IVIg by enzyme-linked immunosorbent assay and by using the BIAcore (BIAcore, Uppsala, Sweden) technology. The affinity of anti-RGD antibodies to a synthetic RGD-containing peptide and to fibronectin (Fn) was found to be in the micromolar range. F(ab′)2 fragments specific for RGD were purified from IVIg by affinity chromatography. Anti-RGD F(ab′)2 antibodies inhibited adenosine diphosphate induced IIb/β3 integrin-mediated platelet aggregation and the adhesion of activated 4β1 integrin-expressing B cells to Fn. Adhesion of unstimulated platelets to fibrinogen (Fg) involving both the γ-chain dodecapeptide sequence and the RGD sequence was inhibited by anti-RGD antibodies. In addition, adhesion of thrombin-stimulated platelets to von Willebrand factor or Fg was completely inhibited by affinity-purified anti-RGD antibodies. Our results suggest that the presence of natural IgG antibodies to the RGD motif may contribute to the immunomodulatory and anti-inflammatory effects of therapeutic preparations of normal IgG.

Inhibition of Cell Adhesion by Antibodies to Arg-Gly-Asp (RGD) in Normal Immunoglobulin for Therapeutic Use (Intravenous Immunoglobulin, IVIg)

Intravenous immunoglobulin (IVIg) therapy is associated with a broad range of immunomodulatory activities. Several of the postulated mechanisms of IVIg action relate to the presence of antibodies to molecules relevant for regulation of the immune response. This article reports that IVIg contains antibodies to the Arg-Gly-Asp (RGD) sequence, and the attachment site of a number of adhesive extracellular matrix proteins, including ligands for β1, β3, and β5 integrins. Anti-RGD antibodies were identified in IVIg by enzyme-linked immunosorbent assay and by using the BIAcore (BIAcore, Uppsala, Sweden) technology. The affinity of anti-RGD antibodies to a synthetic RGD-containing peptide and to fibronectin (Fn) was found to be in the micromolar range. F(ab′)2 fragments specific for RGD were purified from IVIg by affinity chromatography. Anti-RGD F(ab′)2 antibodies inhibited adenosine diphosphate induced IIb/β3 integrin-mediated platelet aggregation and the adhesion of activated 4β1 integrin-expressing B cells to Fn. Adhesion of unstimulated platelets to fibrinogen (Fg) involving both the γ-chain dodecapeptide sequence and the RGD sequence was inhibited by anti-RGD antibodies. In addition, adhesion of thrombin-stimulated platelets to von Willebrand factor or Fg was completely inhibited by affinity-purified anti-RGD antibodies. Our results suggest that the presence of natural IgG antibodies to the RGD motif may contribute to the immunomodulatory and anti-inflammatory effects of therapeutic preparations of normal IgG.

Cell adhesion molecules in invertebrate immunity

Cell adhesion is essential in immunity in invertebrates, e.g., in the cellular immune responses of encapsulation and nodule formation. Here cell adhesion molecules shown or suggested to be involved in invertebrate immunity are reviewed. Blood cells of the crayfish, Pacifastacus leniusculus, can release a cell-adhesive and opsonic peroxidase, peroxinectin. A site containing the motif, KGD, appears to be adhesive by binding to a transmembrane receptor of the integrin family on the blood cells. Peroxinectin also binds a peripheral blood cell surface CuZn-superoxide dismutase. The peroxidase-integrin interaction appears to have evolved early and seems conserved; human myeloperoxidase supports cell adhesion via the alphaMbeta2 integrin. There is evidence for peroxinectin-like proteins in other arthropods. Effects by RGD peptides indicate that integrins mediate blood cell adhesion and cellular immunity in diverse invertebrate species. Other invertebrate blood cell molecules proposed to be involved in adhesion include the insect plasmatocyte-spreading peptide, as well as soluble and transmembrane proteins which show some similarity to vertebrate adhesive or extracellular matrix molecules. Proteins such as the Ig family member hemolin, or proteins found in insects that are hosts for parasitic wasps, inhibit cell adhesion and may regulate or block cellular immunity.

ICAM-2 and a Peptide from Its Binding Domain Are Efficient Activators of Leukocyte Adhesion and Integrin Affinity

Cell adhesion mediated by the CD11/CD18 integrins and their ligands, the ICAMs, is required for many leukocyte functions. In resting cells the integrins are nonadhesive, but when activated they become adhesive for their ligands. Previous findings have shown that a peptide derived from the first Ig domain of ICAM-2 (P1) binds to LFA-1 (CD11a/CD18) and Mac-1 (CD11b/CD18) and activates leukocyte aggregation. Because its mechanism of action has remained poorly understood, we have now studied the peptide-induced ligand binding in detail. Here we show that P1 was able to induce CD11/CD18-dependent adhesion of human T lymphocytes to immobilized, purified ICAM-1, -2, and -3. The optimal peptide concentration was 150 μg/ml, whereas concentrations higher than 400 μg/ml did not have any stimulatory effect. The increase in adhesion was detectable within 10 min of treatment with the peptide; it was dependent on energy, divalent cations, temperature, and an intact cytoskeleton but was unaffected by protein kinase C and protein tyrosine kinase inhibitors. Peptide treatment resulted in strong stimulation of the binding of soluble, recombinant ICAMs to T lymphocytes, showing that the integrin affinity toward its ligands was increased. Importantly, soluble ICAM-2Fc was also able to induce T lymphocyte adhesion to purified ICAM-1, -2, and -3, and it was a more potent stimulatory molecule than ICAM-1Fc or ICAM-3Fc.

Leukocyte adhesion--a fundamental process in leukocyte physiology

Leukocyte adhesion is of pivotal functional importance. The adhesion involves several different adhesion molecules, the most important of which are the leukocyte beta 2-integrins (CD11/CD18), the intercellular adhesion molecules, and the selectins. We and others have extensively studied the specificity and binding sites in the integrins and the intercellular adhesion molecules for their receptors and ligands. The integrins have to become activated to exert their functions but the possible mechanisms of activation remain poorly understood. Importantly, a few novel intercellular adhesion molecules have been recently described, which seem to function only in specific tissues. Furthermore, it is becoming increasingly apparent that changes in integrins and intercellular adhesion molecules are associated with a number of acute and chronic diseases.

Thrombolysis with tissue plasminogen activator alters adhesion molecule expression in the ischemic rat brain

BACKGROUND AND PURPOSE

We tested the hypothesis that treatment of embolic stroke with recombinant human tissue plasminogen activator (rhtPA) alters cerebral expression of adhesion molecules.

METHODS

Male Wistar rats were subjected to middle cerebral artery occlusion by a single fibrin-rich clot. P-selectin, E-selectin, and intercellular adhesion molecule-1 (ICAM-1) immunoreactivity was measured at 6 or 24 hours after embolic stroke in control rats and in rats treated with rhtPA at 1 or 4 hours after stroke. To examine the therapeutic efficacy of combined rhtPA and anti-ICAM-1 antibody treatment at 4 hours after embolization, ischemic lesion volumes were measured in rats treated with rhtPA alone, rats treated with rhtPA and anti-ICAM-1 antibody, and nontreated rats.

RESULTS

Administration of rhtPA at 1 hour after embolization resulted in a significant reduction of adhesion molecule vascular immunoreactivity after embolization in the ipsilateral hemisphere compared with corresponding control rats. However, when rhtPA was administered to rats at 4 hours after embolization, significant increases of adhesion molecule immunoreactivity in the ipsilateral hemisphere were detected. A significant increase of ICAM-1 immunoreactivity was also detected in the contralateral hemisphere at 24 hours after ischemia. A significant reduction in lesion volume was found in rats treated with the combination of rhtPA and anti-ICAM-1 antibody compared with rats treated only with rhtPA.

CONCLUSIONS

The present study suggests that the time of initiation of thrombolytic therapy alters vascular immunoreactivity of inflammatory adhesion molecules in the ischemic brain and that therapeutic benefit can be obtained by combining rhtPA and anti-ICAM-1 antibody treatment 4 hours after stroke.