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PubMed1996

Stimulation of tyrosine phosphorylation after ligation of beta7 and beta1 integrins on human B cells.

B lymphocytes express several members of the integrin family of adhesion molecules that mediate cell-cell and cell-extracellular matrix interactions. In addition to beta1 integrins, predominantly alpha4 beta1, mature B cells also express alpha4 beta7, which is a receptor for vascular cell adhesion molecule-1 and fibronectin, and is also involved in the homing of B cells to mucosal sites through binding to a third ligand, mucosal address in cell adhesion molecule-1. Here we describe that crosslinking of alpha4 beta7 integrins on B cell lines and normal tonsillar B cells, induces tyrosine phosphorylation of multiple substrates of 105-130 kD, indicating that beta7 integrin plays a role as signaling molecule in B cells. This pattern of phosphorylated proteins was very similar to that induced following ligation of alpha4 beta1. Interestingly, ligation of alpha5 beta1 or alpha6 beta1 also stimulated the 105-125 kD group of phosphorylated proteins, whereas ligation of beta2 integrins did not. The focal adhesion tyrosine kinase p125FAK was identified as one of these substrates. Beta1 or beta7 mediated tyrosine phosphorylations were markedly decreased when the microfilament assembly was inhibited by cytochalasin B. These results suggest that intracellular signals initiated by different integrins in B cells may converge, to similar cytoskeleton-dependent tyrosine phosphorylated proteins.

Antibodies, Monoclonal↗
PubMed1996

Differential regulation of leukocyte function-associated antigen-1/ intercellular adhesion molecules-1-dependent adhesion and aggregation in HL-60 cells.

Activation of integrin and organization of cytoskeletal proteins are highly regulated in cell adhesion and aggregation. The interaction of leukocyte function-associated antigen-1 (LFA-1) and intercellular adhesion molecules-1 (ICAM-1) mediates cell adhesion and aggregation, which facilitate leukocyte trafficking to inflamed tissues and augment effector functions. We investigated how LFA-1/ICAM-1-mediated adhesion and aggregation are regulated in HL-60 cells induced to differentiate into neutrophils by retinoic acid (RA). Uninduced HL-60 cells did not bind to ICAM-1 even with stimulation by 12-0-tetradecanoyl phorbol-13-acetate, although they express LFA-1 on the cell surface. When cultured with RA for 24 hours, HL-60 cells were able to adhere to ICAM-1 constitutively. The induction of adhesion did not accompany any change in surface density of LFA-1, indicating that the avidity of LFA-1 was increased. The change in its avidity required de novo synthesis of proteins. Although ICAM-1 was intensely expressed on RA-induced HL-60 cells, these cells did not show any cellular aggregation. The HL-60 cells transfected with the active form of Ras (Val12) exhibited LFA-1/ICAM-1-dependent aggregation by RA stimulation without change in the avidity of LFA-1. In these Ras-transfectants, a cytoskeletal protein, paxillin, was tyrosine-phosphorylated, and the level of F-actin increased. Transforming growth factor (TGF) beta, as well as cytochalasin D, prevented both the tyrosine phosphorylation of paxillin and the aggregation without any effects on the avidity of LFA-1. Thus, an increase in the avidity of LFA-1 was not sufficient for the induction of aggregation, which required activation of Ras and reorganization of cytoskeletal proteins. These results suggest that distinct regulatory mechanisms control LFA-1/ICAM-1-dependent adhesion and aggregation in HL-60 cells differentiating into neutrophils.

Actins↗
PubMed1996

Integrin function in chronic lymphocytic leukemia.

Integrins are central to many aspects of the tissue localization of normal and malignant lymphocytes. We examined how integrin function, rather than simple expression, might determine disease behavior in chronic lymphocyte leukemia (CLL). Using fluorescence-activated cell sorting (FACS) and immunoprecipitation, we first established the precise integrin heterodimer expression of a representative group of CLL patients (beta1 consistently present, with variable alpha 3, alpha 4, and alpha 5; alpha 4 beta 7 often expressed; alpha L beta 2 high; alpha V beta 3 absent). Regarding function, we initially examined the ability of CLL cells to interact with endothelium, because such interaction is the initial event determining the entry of CLL lymphocytes into tissues. The abnormal lymphocytes were shown to bind at low levels to unstimulated endothelium via beta 2/intercellular adhesion molecule (ICAM). However, when the endothelium was stimulated, markedly enhanced interaction with endothelium was observed in approximately half the cases; in these patients, the neoplastic population expressed alpha 4 beta 1, which conferred the ability to adhere strongly to stimulated endothelium via the alpha 4 beta 1 ligand, vascular cellular adhesion molecule-1 (VCAM-1). In relation to the migration of CLL cells within tissues, the abnormal lymphocytes showed differential binding to various adhesive proteins; they did not attach to basement membrane components, but displayed variable adhesion to fibronectin (FN). Finally, we examined the role of cell activation in these processes, and showed that activated CLL lymphocyte populations showed an increased capacity to adhere to both endothelium and matrix. Moreover, ex vivo CLL cells showed no capacity to migrate through endothelium/stroma, but were able to do so after cytokine stimulation. These studies show how the constitutive integrin expression/function, the intrinsic activation state of the cell, and the capacity of cytokines to modify integrin-mediated function all combine to determine the different patterns of clinical disease observed in CLL.

B-Lymphocytes↗
PubMed1996

Glycoprotein IV-independent adhesion of sickle red blood cells to immobilized thrombospondin under flow conditions.

The abnormal adherence of red blood cells (RBC to the blood vessel wall is believed to contribute to the vascular occlusion observed in patients with sickle call anemia. The cell adhesion receptors GPIV (CD36) and integrin alpha 4 beta 1 (CD49d/CD29) were previously identified on circulating sickle reticulocytes, and shown to mediate sickle RBC adhesion to the endothelium. The presence of damaged endothelium in these patients suggests that exposed extracellular matrix proteins could provide a potential substrate for sickle RBC adhesion. To determine whether RBC adhesion receptors could mediate adhesion to extracellular matrix proteins, we tested their ability to adhere to a variety of immobilized, purified proteins under flow conditions. Neither sickle nor normal RBC adhered to fibronectin, vitronectin, fibrinogen, or collagen. In contrast, we observed substantial adhesion of sickle but not normal RBC to thrombospondin (TSP). The adhesion was not inhibited with known antagonists of the GPIV-TSP interaction, nor by inhibitors of several other known binding domains in TSP. Moreover, the adhesion was resistant to inhibition by soluble TSP, suggesting that immobilization of TSP exposes an adhesive site that is cryptic on TSP in solution. However, the glycosaminoglycans, chondroitin sulfate A, and dextran sulfate were potent inhibitors of this adhesion. These results suggest that a mechanism distinct from GPIV is responsible for sickle RBC adhesion to immobilized TSP under flow conditions.

Aggrecans↗
PubMed1996

NK cell infiltration into lung, liver, and subcutaneous B16 melanoma is mediated by VCAM-1/VLA-4 interaction.

The mechanisms that regulate the adhesion and migration of NK cells to and across endothelium have been studied under nonflow conditions; however, the involvement of these processes in vivo is poorly understood. The present studies investigated the potential vascular adhesion ligand interactions that determine the in vivo recruitment of NK cells to pulmonary and hepatic parenchyma, and s.c. tumor after treatment of mice with biologic response modifiers. Seventy-two hours after a single injection of the cytokine-inducing agent poly-L-lysine stabilized in carboxylmethyl cellulose (poly-ICLC), pulmonary NK cell lytic activity and N-alpha-carbobenzoxy-L-lysine thiobenzyl ester (BLT)-esterase were augmented 29- and 14-fold, respectively, and the number of lung-associated NK cells was increased from 2.3 x 10(5) to 7.4 x 10(5). Similar fold increases in NK cell number and activity were observed in the liver and s.c. B16 melanoma after poly-ICLC injection or in the lungs and liver of mice treated with IL-2. Concomitant treatment of mice with alpha-VCAM-1 or alpha-VLA-4 mAb, but not alpha-ICAM-1 or alpha-LFA-1, abrogated the poly-ICLC and IL-2-induced increase in organ-associated NK activity and percentage of tumor-associated NK cells, resulted in a 61 to 76% decrease in pulmonary and hepatic NK cell number, and was independent of T and/or B cells. The decrease in NK cell number in organ parenchyma and tumor lesions was correlated to an increase in the number of NK cells in peripheral blood, but not bone marrow. These results demonstrate that VCAM-1/VLA-4 interaction is critically involved in the infiltration of newly recruited NK cells in to lung, liver, and progressively growing tumor after mobilization from the bone marrow.

Animals↗
PubMed1995

VLA-4-dependent adhesion in follicular non-Hodgkin's lymphomas.

The cellular contact between B cells and follicular dendritic cells (FDCs) in the germinal center is thought to play a key role in B-cell maturation and proliferation. The adhesion pathway through the very late antigen 4 (VLA-4) on the B cells and the vascular cell adhesion molecule 1 (VCAM-1) on the FDCs support this binding process. The neoplastic follicular centers in follicular non-Hodgkin's lymphomas (FNHLs) have similar structures and cellular components to those of normal germinal centers, but their interaction between B cells and FDCs may be functionally disturbed. In view of this we analyzed the interaction between VLA-4 and VCAM-1 molecules in the germinal center microenvironment, both in neoplastic and normal follicles. The structural characterization of FNHLs and reactive lymph nodes was studied with indirect immunohistochemical stainings using monoclonal antibodies against VLA-4, VCAM-1, and fibronectin, with special reference to the reaction pattern in the normal and neoplastic follicles. In the reactive follicular centers most B cells did not show a positive reaction for VLA-4, except for moderate reaction products in the B cells of the light zone. In FNHLs, on the other hand, most follicular center B cells were positive for VLA-4. The reaction patterns of VCAM-1 and fibronectin in both normal and neoplastic follicular centers were not basically different. To investigate the interaction of VLA-4 with VCAM-1 in both neoplastic and normal follicular centers, we performed a frozen-section binding assay, which found decreased binding between VLA-4 and VCAM-1 in FNHLs. The results of this study indicated that the microenvironment in neoplastic follicular centers is different from that in their normal counterparts, in terms of the characteristic distribution pattern of the VLA-4-positive B cells, and the functional deterioration of the VCAM-1 on FDCs.

Cell Adhesion↗
PubMed1996

L- and P-selectins, but not CD49d (VLA-4) integrins, mediate monocyte initial attachment to TNF-alpha-activated vascular endothelium under flow in vitro.

Monocyte adhesion to the vascular endothelium is a pivotal step during their egress to tissues at sites of inflammation and immune reactions, and during atherogenesis. In this study, an in vitro flow model and blocking mAb were used to define the role of adhesion molecules in monocyte interactions with activated HUVEC under flow conditions. By videomicroscopy, freely flowing monocytes abruptly halted (initial attachment) on 6-h TNF-alpha-activated HUVEC under flow via L- and P-selectin, whereas E-selectin was not involved. CD49d/CD29 integrin (VLA-4), which can mediate initial attachment of certain T cells to VCAM-1 under flow, did not support monocyte initial attachment. Once initially attached, a small number of monocytes began rolling at 9 microns/s through a mechanism involving L-selectin, as well as CD49d and CD11/CD18 integrins, while the remaining monocytes became firmly adherent, or released to the flow stream. Monocyte stable arrest and subsequent transendothelial migration occurred rapidly and efficiently through either CD49d or CD18 integrin adhesion pathways. Transendothelial passage was also dependent on PECAM-1 (CD31). These data reveal monocytes initially attach to activated endothelium via an L-selectin-dependent mechanism, with a smaller contribution from P-selectin and no contribution by CD49d. Subsequent monocyte rolling, arrest, and transmigration require overlapping functions between multiple members of the selectin, integrin, and Ig gene families.

Animals↗
PubMed1996

Cytokine regulation of proliferation and cell adhesion are correlated events in human CD34+ hemopoietic progenitors.

Adhesive interactions with the extracellular matrix of the bone marrow (BM) stroma are of critical importance in the regulation of hematopoiesis. In part, these interactions are presumed to play an important role in retaining CD34+ hematopoietic progenitor cells (HPCs) within the BM environment, in close proximity with BM stromal cells and the cytokines they produce. Evidence of a more direct role for cell adhesion in the regulation of hematopoiesis is provided by recent data showing that adhesive interactions can also provide important costimulatory signals. We have previously shown that normal CD34+ HPCs express high levels of fibronectin (Fn) receptors very late antigen-4 (VLA-4) and VLA-5 in a low-affinity state, which do not allow HPCs to strongly adhere on immobilized Fn, and that cytokines such as interleukin-3, granulocyte-monocyte colony-stimulating factor, and stem cell factor transiently activate these receptors, providing HPCs with an adhesive phenotype on Fn. Thus, knowledge of the functional states of adhesion receptors is critical to our understanding of the physiological mechanisms responsible for the regulation of normal hematopoiesis. Herein, we show that combinations of cytokines that synergize to stimulate the proliferation of CD34+ HPCs result in additive stimulation of the adhesion of these cells to Fn. Thus, the activation level of Fn receptors expressed by normal CD34+ HPCs is highly correlated with their proliferative state, suggesting a functional link between these two events. Therefore, we propose a 2-step model with an initial activation of VLA-4 and VLA-5 generated by cytokine receptors that is followed by a secondary signal resulting from Fn binding to VLA-4 and VLA-5, which may cooperate with those generated by cytokine receptors.

Adult↗
PubMed1996

HST-1/FGF-4 stimulates proliferation of megakaryocyte progenitors synergistically and promotes megakaryocyte maturation.

Megakaryocyte (MK) development is dependent on the complex interaction of MK progenitors, various cytokines and stromal elements. We previously reported that an injection of replication-deficient adenovirus containing HST-1/FGF-4 cDNA (Adex1HST-1) into mice caused a twofold increase in peripheral platelet count for 30 days without any other hematological or histological abnormality. In the present study using Adex1HST-1-infected human megakaryocytic Dami cells, we demonstrated for the first time that HST-1/FGF-4 promoted MK maturation, inducing increases in DNA ploidy, cytoplasmic and membrane maturation, and platelet-like particle release. Moreover, HST-1/FGF-4 acted on megakaryocytic cells to induce secretion of IL-6 and TNF-alpha, and increased adhesion of megakaryocytic cells to human endothelial cells primarily via VLA-4 and LFA-1 molecules; both mechanisms have been shown to lead to MK maturation. We also showed that HST-1/FGF-4 stimulates the proliferation of MK progenitors not alone but synergistically with IL-3 via IL-6 and with c-mpl ligand (thrombopoietin) not via IL-6. This result supports the hypothesis of the presence of two distinct populations of MK progenitors: IL-3-dependent and Tpo-dependent. All these results suggest that HST-1/FGF-4 can regulate MK development not only as an MK potentiating factor, but also as an inducer of cytokine secretion from MK, and as a modulator of adhesive interactions with endothelial cells.

Adenoviruses, Human↗
PubMed1996

Effects of mycophenolic acid mofetil on acute rejection of kidney allografts in rats.

Mycophenolic acid mofetil (MMF) is an agent which has recently gained a lot of attention. In clinical trials MMF has reduced the rate of acute rejection episodes in human recipients of kidney allografts by inhibiting inosin-monophosphat-dehydrogenasis (IMPDH), an enzyme involved in the purin metabolism and related to the expression of adhesion molecules. The aim of the present study was to analyze the effects of MMF upon the expression of adhesion molecules in transplanted kidney allografts. LBNF1 kidneys were orthotopically transplanted into Lewis rats and either treated with MMF (20 mg/kg/day) or vehicle. Rats were harvested 3, 5 and 7 days following transplantation. Immunohistology was performed with various monoclonal antibodies. In general, MMF resulted in a better preservation of graft structure by 7 days. Cellular infiltration and tubular atrophy were less pronounced. At day 3, macrophages were diminished in MMF-treated animals to a high extent, while the number of T-cells was almost identical as compared to controls. In addition, the number of cells positive for MHC class II and LFA-1 was reduced in the MMF-treated animals. In conclusion, MMF resulted in a markedly reduced leukocyte infiltrate, presumably based on a reduced expression of lymphocytic adhesion molecules and an interaction with macrophages.

Animals↗
PubMed1996

Alpha 4 beta 1 (CD49d/CD29) integrin costimulation of human T cells enhances transcription factor and cytokine induction in the absence of altered sensitivity to anti-CD3 stimulation.

The integrin alpha 4 beta 1 can provide a costimulus to induce IL-2 secretion and IL-2R expression leading to enhanced proliferation of purified, peripheral blood T cells. Similar to expression of IL-2, we demonstrated that recombinant vascular-cell adhesion molecule-1, when co-immobilized with anti-CD3 mAb, significantly enhanced the induction of transcription factors NF-AT, AP-1, and NF-kappa B as determined by electromobility shift assays. alpha 4 beta 1 ligation alone had no effect on transcription factor binding. The requirements for induction of transcription factors reflected the requirements for the secretion of multiple cytokines, including IL-2, TNF-alpha, IFN-gamma, and granulocyte macrophage-CSF. In contrast to freshly isolated T cells, in vitro-cultured T cells did not require costimulation for cytokine secretion in response to anti-CD3 alone. Comparison of the dose response to anti-CD3 stimulation demonstrated that half-maximal induction of IL-2 was achieved using the same dose of anti-CD3 for both freshly isolated and cultured T cells. Furthermore, the dose of OKT3 required to achieve half-maximal activation was the same using PMA or different concentrations of alpha 4 beta 1 ligands. Therefore, costimulation by alpha 4 beta 1 ligands was not due to stabilization of the interaction of the cells with its substrate. We conclude, rather, that alpha 4 beta 1 in freshly isolated T cells delivers a distinct signal that synergizes early with signals initiated by TCR/CD3 ligation to induce DNA binding of multiple transcription factors required for cytokine gene induction.

CD3 Complex↗
PubMed1996

Transmembrane-4 superfamily proteins CD81 (TAPA-1), CD82, CD63, and CD53 specifically associated with integrin alpha 4 beta 1 (CD49d/CD29).

Anti-alpha 4 integrin mAb coprecipitated CD81 (TAPA-1), a 25-kDa cell surface protein, from various alpha 4 beta1 -positive hemopoietic cell lines, including Molt4, Jurkat, Ramos, and alpha 4-transfected K562 (KX4C4) cells. In reciprocal experiments, the integrin alpha 4 beta 1 (VLA4, CD49d/CD29) could be reprecipitated from CD81 immunoprecipitates. Anti-alpha 4 integrin mAb also coprecipitated CD81 from the alpha 4 beta 7-positive B cell line RPMI 8866. In contrast, no CD81 was identified in alpha 2 beta 1, alpha 5 beta 1, or alpha L beta 2 immunoprecipitates. Abs to other members of the transmembrane-4 superfamily, including CD53, CD63, and CD82, also coprecipitated alpha 4 beta 1. As shown by confocal microscopy, CD81 and CD82 colocalized with alpha 4 beta 1 in cell surface clusters. The cytoplasmic domain of the alpha 4 integrin was not necessary for alpha 4 beta 1/CD81 association, nor was the association influenced by divalent cations, EDTA, integrin-activating mAb, or alpha 4 subunit cleavage. Notably, two independent alpha 4 adhesion-deficient mutants (D346E and D408E) were deficient in their ability to associate with CD81. Thus, CD81 and other transmembrane-4 superfamily members may participate in functionally relevant interactions with alpha 4 beta 1 and other integrins.

Antibodies, Monoclonal↗
PubMed1996

Endometrial progesterone receptors and markers of uterine receptivity in the window of implantation.

OBJECTIVE: To compare the expression of endometrial P receptors (PR) levels with markers of endometrial receptivity during the window of implantation. DESIGN: Prospective, controlled study to examine endometrial PR and three cycle-specific integrins in endometrial biopsies obtained during the window of implantation. SETTING: An academic teaching hospital. PATIENTS: One hundred seventy-five endometrial biopsies from regularly cycling women with luteal phase defect (LPD; group 1; n = 80), medically treated LPD (group 2; n = 16), minimal and mild endometriosis with aberrant alpha v beta 3 expression (group 3; n = 21), fertile controls (group 4; n = 26), and infertile controls (group 5; n = 32). MAIN OUTCOME MEASURE: Immunohistochemical staining intensity of each antigen using the semi-quantitative grading system (HSCORE), compared using analysis of variance with Scheffe's correction. RESULTS: Among the five groups studied, nuclear PR expression was significantly elevated in glandular epithelial cells from tissue samples with histologic delay > or = 3 days consistent with luteal phase deficiency (LPD; group 1). Failure of PR down-regulation was associated with aberrant alpha v beta 3 integrin expression. Medical correction of LPD was associated with return of normal endometrial histology, normal integrin expression, and the loss of epithelial PR, similar to controls. The other two cycle-dependent integrin markers, alpha 1 beta 1 and alpha 4 beta 1, were not different between groups. In women with aberrant alpha v beta 3 and "in phase" endometrium, epithelial PR expression was not different from controls. CONCLUSIONS: The establishment of normal endometrial receptivity appears to be tightly associated with the down-regulation of epithelial PR. Histologic delay, consistent with LPD, is associated with a failure of PR down-regulation and the lack of normal markers of endometrial receptivity. Occult uterine receptivity defects (aberrant beta 3 expression in otherwise normal histology) are regulated differently, suggesting alternate mechanisms also exist which influence endometrial receptivity.

Adult↗
PubMed1996

The effect of oral contraceptive pills on markers of endometrial receptivity.

OBJECTIVE: To determine if oral contraceptive (OC) usage alters expression of integrins associated with endometrial receptivity. DESIGN: Immunohistochemical staining intensity for integrins was compared in frozen sections of endometrial tissue specimens obtained from women with normal ovulatory cycles (n = 23; cycle days 20 to 24 based on LH surge) and from those taking oral contraceptives pills (n = 23; cycle days 5 to 27). SETTING: University-based outpatient infertility clinic. RESULTS: Constitutive integrin expression in the endometrium (alpha 2 beta 1, alpha 3 beta 1, alpha 5 beta 1, alpha 6 beta 1, and alpha 6 beta 4) was similar in OC users and normally cycling individuals, except for an increase in epithelial alpha 3 beta 1 in OC users. Oral contraceptive use was associated with significant alterations in cycle-dependent integrin expression (alpha 1 beta 1, alpha 4 beta 1, and alpha v beta 3). Specifically, we observed increased glandular alpha 4 beta 1, and decreased alpha v beta 3 expression. The P-regulated alpha 1 subunit was present in both groups. Increased stromal alpha v and beta 3 and decreased alpha 3 beta 1 and alpha 6 beta 1 staining was observed in OC users. CONCLUSIONS: Expression of those integrins most closely associated with endometrial receptivity, alpha v beta 3 and alpha 4 beta 1, is altered in the glandular epithelium of women taking OCs. Stromal integrin expression in OC users also differs from that in cycling women. These alterations in epithelial and stromal integrin expression suggest that impaired uterine receptivity is one mechanism whereby OCs exert their contraceptive actions.

Adult↗
PubMed1996

[Allo-cytotoxic T lymphocyte responses in corneal allografted mice treated with monoclonal antibodies to adhesion molecules].

Corneal transplantation was performed by grafting C3H/He donor corneas into BALB/c corneal beds. The allografted mice were injected either with 0.5 mg/day of anti-very late antigen (VLA)-4 antibody, anti-leukocyte function-associated antigen (LFA)-1 antibody, or 0.25 mg/day each of both antibodies on days -2, 0, 1, 3, 5, and 7. After 3 weeks, cytotoxic T lymphocyte (CTL) responses to donor alloantigens were assessed. Splenocytes in the allografted mice without treatment demonstrated greater CTL responses that those in naive mice. CTL responses were depressed in mice treated with either anti-LFA-1 alone or a combination of anti-LFA-1 and anti-VLA-4 antibodies as compared with splenocytes from allografted mice without treatment. These data suggest that CTLs play significant roles in eliciting immune response to corneal allografts.

Animals↗
PubMed1996

The role of alpha 4 integrins in lung pathophysiology.

The alpha 4 integrins are heterodimeric leucocyte cell surface molecules central to their cell and matrix adhesive interactions. The integrin alpha 4 beta 1 interacts with the immunoglobulin superfamily member vascular cell adhesion molecule-1 (VCAM-1), and with an alternatively spliced form of fibronectin. The integrin alpha 4 beta 7 binds not only VCAM-1 and fibronectin, but also the mucosal addressin cell adhesion molecule (MAdCAM). Certain monoclonal antibodies (MoAbs) to the alpha 4 chain of alpha 4 beta 1 and alpha 4 beta 7 can block their in vitro adhesive function. In vivo studies with these MoAbs in lung antigen challenge models in several species demonstrate that alpha 4 integrins play a key role in eosinophil and T-cell recruitment, in the late phase response, and in airways hyperresponsiveness. In particular, MoAb HP1/2 is efficacious in a sheep model of allergic airways challenge, whether given intravenously or as aerosol. To evaluate the mechanism of action of this MoAb, Fab fragments were generated and shown to be equipotent in vitro and as efficacious in vivo as the intact immunoglobulin G (IgG). These data demonstrate that the in vivo efficacy of monoclonal antibody HP1/2 is not due to indirect effects, such as antigen cross-linking, but rather to blockade of alpha 4 integrin adhesive function. Humanized monoclonal antibody or other alpha 4 integrin antagonists may provide novel therapeutics for asthma.

Alternative Splicing↗
PubMed1996

Role of the eosinophil in allergic reactions.

The eosinophil may have several functions in health and in the pathogenesis of allergic and other diseases. Some roles of the eosinophil are based on the acute, effector responses of this cell, its capacity to generate biologically active lipid mediators and release its granule contents, including its distinctive cationic proteins. Whilst the effector responses of eosinophils are important for their contribution to the acute pathogenesis of allergic diseases, a fuller understanding of the eosinophil requires evaluation of the role this cell may play at tissue sites, especially submucosal sites, where the cell is normally localized in the absence of disease. Moreover, for the long-lived, tissue-resident eosinophil, definition of the interactions that occur between the eosinophil and other immune cells is germane to understanding the functions of eosinophils both in acute and chronic diseases. Many allergic diseases are characterized by heightened accumulation of eosinophils and are chronic ongoing diseases.

Animals↗