Biomedical subjects

R P Andrews

Publications and source records attributed to R P Andrews.

At least 19 recordsLinked to original sources

PubMed2001

Real time analysis of the affinity regulation of alpha 4-integrin. The physiologically activated receptor is intermediate in affinity between resting and Mn(2+) or antibody activation.

This work examines the affinity of alpha(4)beta(1)-integrin and whether affinity regulation by G protein-coupled receptor (GPCR) and chemokines receptors is compatible with cell adhesion mediated between alpha(4)-integrin and vascular cell adhesion molecule-1. We used flow cytometry to examine the binding of a fluorescent derivative of an LDV peptide (Chen, L. L., Whitty, A., Lobb, R. R., Adams, S. P., and Pepinsky, R. B. (1999) J. Biol. Chem. 274, 13167-13175) to several cell lines and leukocytes with alpha(4)-integrin ranging from about 2,000 to 100,000 sites/cell. The results support the idea that alpha(4)-integrins exhibit multiple affinities and that affinity changes are regulated by the dissociation rate and conformation. The affinity varies by 3 orders of magnitude with the affinity induced by binding mAb TS2/16 plus Mn(2+) > Mn(2+) ' TS2/16 > activation because of occupancy of GPCR or chemokines receptor > resting receptors. A significant fraction of the receptors respond to the activating process. The change in alpha(4)-integrin affinity and the corresponding change in off rates mediated by GPCR receptor activation are rapid and transient, and their duration depends on GPCR desensitization. The affinity changes mediated by IgE receptor or interleukin-5 receptor persist longer. It appears that the physiologically active state of the alpha(4)-integrin, determined by inside-out signaling, has similar affinity in several cell types.

Antibodies, Monoclonal↗

PubMed2001

Analysis of the Ser786Pro interleukin-4 receptor alpha allelic variant in allergic and nonallergic asthma and its functional consequences.

Asthma and other atopic disorders affect a large percentage of the population. While many factors contribute to the phenotype of asthma, there is a strong genetic predisposition. IL-4 is a central mediator of allergic inflammation. Along with IL-13, it is the major cytokine responsible for the induction of IgE synthesis. Furthermore, IL-4 acts on Th0 cells and promotes their differentiation into Th2 cells resulting in the production of more IL-4 and IL-13, thereby propagating the allergic cascade. Both IL-4 and IL-13 utilize IL-4Ralpha as a component of their cognate receptor complexes. Eight polymorphisms of the IL-4Ralpha gene resulting in amino acid changes in the coding sequence have been described, and several have been associated with asthma. The central objective of this study was to elucidate the role of the Ser786Pro polymorphism in asthma and its impact on IL-4R function. One-hundred ninety-six individuals with asthma and 53 controls were genotyped for Pro786. Pro786 occurred infrequently in the general population with an allele frequency of 1.8% and, thus, is unlikely to play a major role in atopy or asthma. The Pro786 allele frequency was 1.5% in the asthma group and 2.8% in the control group. The asthma group was subdivided into allergic and nonallergic asthma, and the Pro786 allele frequencies were 1.7 and 1.0%, respectively. The data suggested linkage disequilibrium between Ser786Pro and the Gln576Arg allele, which is associated with atopy. In order to study the impact of the polymorphism on receptor signaling function, we transfected a mouse B lymphoma cell line with the wild-type and Pro786 variants of human IL-4Ralpha. The Ser786Pro polymorphism in isolation did not affect IL-4R function.

Adult↗

PubMed2001

Sulfhydryl-2 domain-containing protein tyrosine phosphatase-1 is not a negative regulator of interleukin-4 signaling in murine mast cells.

Sulfhydryl-2 domain-containing tyrosine phosphatase-1 (SHP-1) has an important role in the negative regulation of many receptors including the interleukin (IL)-4 receptor. Motheaten mice (me/me) have a homozygous mutation in SHP-1 and do not possess functional SHP-1. Pre-B-cell lines derived from me/me mice have been reported to display prolonged IL-4-dependent activation of signal transducer and activator of transcription-6 (Stat6). We evaluated IL-4-dependent Stat6 activation and Fcepsilon receptor 1 (FcepsilonRI) modulation in bone marrow-derived mast cells (BMMCs) from me/me and wild-type mice. IL-4 down-regulated FcepsilonRI expression in wild-type BMMCs but had no effect on FcepsilonRI expression in me/me BMMCS: Furthermore, me/me mast cells did not exhibit enhanced or prolonged IL-4-induced Stat6 activation compared with wild-type cells, indicating that mast cells possess alternative tyrosine phosphatases that are responsible for down-regulating Stat6 or can substitute for SHP-1. Thus, SHP-1 is not a negative regulator of IL-4 signaling in BMMCS: These results demonstrate the complexity and cellular specificity of these signaling pathways and indicate a previously unrecognized role for SHP-1 in murine mast cells.

Animals↗

PubMed2001

Regulation of the very late antigen-4-mediated adhesive activity of normal and nonreleaser basophils: roles for Src, Syk, and phosphatidylinositol 3-kinase.

Normal human basophils express the integrin, VLA-4, and cross-linking their high-affinity IgE receptor, FcepsilonRI, increases their VLA-4-dependent adhesion to VCAM-1-transfected Chinese hamster ovary (CHO) cells. Here we show that the FcepsilonRI-mediated up-regulation of normal basophil VLA-4 adhesion is abolished by the Src inhibitor, PP1, the Syk inhibitor, ER-27319, and the phosphatidylinositol 3-kinase inhibitor, wortmannin. PP1, but not ER-27319 or wortmannin, also reduces basal adhesion and adhesion stimulated by chemotactic peptide, by Ca(++) ionophores, and by phorbol myristate acetate (PMA). Nonreleaser basophils (the consistently Syk-deficient, variably Lyn-deficient, severely degranulation-impaired cells found in about 10% of donors) share the PP1 phenotype of lowered basal adhesion, no FcepsilonRI-mediated adhesion up-regulation, and reduced adhesive responses to chemoattractant ionophores and PMA. These results implicate Src kinases in the control of basal VLA-4 activity and place Syk and phosphatidylinositol 3-kinase in the pathway linking FcepsilonRI cross-linking to VLA-4 up-regulation. Both Src and Syk-regulated components of adhesion may be impaired in nonreleaser basophils.

Acridines↗

PubMed2000

Multiple defects in Fc epsilon RI signaling in Syk-deficient nonreleaser basophils and IL-3-induced recovery of Syk expression and secretion.

Human basophils respond to Ag-induced cross-linking of their high affinity IgE receptor, FcepsilonRI, by releasing histamine and other mediators from granules, producing IL-4 and other cytokines and, as shown in this study, by forming membrane ruffles and showing increased very late Ag-4 (VLA-4)-mediated adhesion to VCAM-1-expressing target cells. We have identified five blood donors whose basophils lack detectable levels of the FcepsilonRI-associated protein tyrosine kinase, Syk. Despite showing no obvious ultrastructural differences from normal basophils, nonreleaser basophils fail to form membrane ruffles, to show increased VLA-4-mediated adhesive activity, or to produce IL-4 in response to FcepsilonRI cross-linking. Although Syk protein levels are suppressed in basophils from all five donors, Syk mRNA is consistently present. Furthermore, culturing nonreleaser basophils for 4 days with IL-3 restores Syk protein expression and FcepsilonRI-mediated histamine release. Understanding the reversible suppression of Syk protein expression in nonreleaser basophils, and learning to replicate this property in patients with allergic inflammation could be a powerful and specific way to limit symptomatic disease.

Antibodies, Anti-Idiotypic↗

PubMed1999

Syk deficiency in nonreleaser basophils.

BACKGROUND: Peripheral blood basophils from 10% to 20% of donors fail to degranulate in response to cross-linking the high-affinity IgE receptor FcepsilonRI. The molecular mechanisms underlying the nonreleaser phenotype have not been established. OBJECTIVES: Our aim was to compare the expression of FcepsilonRI-associated protein tyrosine kinases between nonreleaser and releaser basophils. METHODS: With use of Western blotting we investigated Syk and Lyn protein levels in highly purified basophils from 3 anti-IgE nonreleasers and 2 releasers. RESULTS: We identified 3 healthy nonatopic donors whose nonreleaser basophils express FcepsilonRI normally but fail to express protein for the tyrosine kinase Syk, which is implicated in the initiation of FcepsilonRI-mediated secretion. Protein levels for the tyrosine kinase Lyn are somewhat reduced but not absent in nonreleaser basophils. Levels of Lyn and Syk protein are similar in B cells, eosinophils, and neutrophils from releaser and nonreleaser donors. During these studies one nonreleaser "converted" into a releaser with concomitant basophil Syk expression. CONCLUSION: The absence of detectable Syk could explain the nonreleaser phenotype of basophils from some donors.

Adolescent↗

PubMed1998

Expression, structure, and location of epitopes of the major surface glycoprotein of Pneumocystis carinii f. sp. carinii.

The major surface glycoprotein (MSG) of Pneumocystis carinii f. sp. carinii consists of a heterogeneous family of proteins that are encoded by approximately 100 unique genes. A genomic expression library was screened with a panel of MSG-specific monoclonal antibodies (MAbs) to identify conserved and rare epitopes. All of the antibodies reacted with epitopes that are encoded within the 5' end of MSG. The results from the expression screening identified antibodies that recognize highly conserved, moderately conserved, and rare epitopes. Four MAbs (MAbs RA-F1, RA-E7, RA-G10, and RB-E3) reacted with a maltose binding protein-MSG-B fusion protein ([MBP]MSG-B41-1065) by immunoblotting and enzyme-linked immunosorbent assay. Three of the MAbs (MAbs RA-F1, RA-G10, and RA-E7) reacted with the same continuous epitope that was localized to amino acids 278 to 290 of MSG-B. Comparison of the sequence of the RA-F1-, RA-G10-, and RA-E7-reactive epitope to the deduced amino acid sequences of multiple MSGs demonstrated that it is highly conserved. The reactivity of RB-E3 with MSG-B was shown to be dependent on amino acids 184 to 192, which may comprise a portion of a discontinuous epitope.

Animals↗

PubMed1997

The carbohydrate recognition domain of surfactant protein A mediates binding to the major surface glycoprotein of Pneumocystis carinii.

Pneumocystis carinii is a common cause of life-threatening pneumonia in immunodeficient patients. Pulmonary surfactant protein A (SP-A), an alveolar glycoprotein containing collagen-like and carbohydrate recognition domains (CRD), binds P. carinii and enhances adherence to alveolar macrophages. In this study, we examined the structural basis of the interaction between SP-A and the major surface glycoprotein of P. carinii (MSG). Rat SP-A bound to purified rat P. carinii-derived MSG in a saturable and calcium-dependent manner, which was partially reversible by coincubation with excess monosaccharides, or pretreatment of MSG with N-glycanase. Mutant recombinant SP-As with neutral amino acid substitutions for the predicted calcium- and carbohydrate-coordinating residues of the CRD were synthesized in insect cells using baculovirus vectors and tested for binding to MSG. Substitutions of negatively charged (Glu195, Glu202, and Asp215) and polar residues (Asn214) of the CRD with alanine but not substitution of the Arg197 with glycine reduced the binding of SP-A to mannose-Sepharose beads and to MSG. Deletion of the N-linked oligosaccharides from SP-A by mutagenesis of the consensus sequences for glycosylation had no effect on binding. We conclude that the CRD mediates the binding of SP-A to oligosaccharides attached to MSG.

Animals↗

PubMed1995

Adoptive transfer of lymphocytes sensitized to the major surface glycoprotein of Pneumocystis carinii confers protection in the rat.

Pneumocystis carinii is a major opportunistic pathogen and a leading cause of morbidity in patients with AIDS. CD4+ cells have been shown to be important in host defenses against P. carinii, but the antigen(s) involved with this response have not been identified. We undertook the present study to determine whether the major surface glycoprotein (MSG) of P. carinii contains epitopes that can elicit a protective cellular immune response. Spleen cells and purified CD4+ cells isolated from Lewis rats, pulsed 1-4 d with MSG, and injected into corticosteroid-treated Lewis rats with pneumocystosis resulted in significant reduction in the P. carinii burden, as judged by organism quantitation and lung histology. The protective response demonstrated by the donor cells was dependent on previous exposure to P. carinii, cell concentration, and time of incubation with MSG. In addition, reconstitution with MSG-specific CD4+ cells resulted in an early hyperinflammatory response within the lungs of these animals with a high percentage of mortality. Thus, in this model, MSG can elicit an immune response mediated by CD4+ cells, which has a harmful as well as helpful effect on the host, and these responses occur despite the presence of corticosteroids.

Animals↗

PubMed1993

Proliferative and cytokine responses to a major surface glycoprotein of Pneumocystis carinii.

Naturally derived T-cell responses by rats to a 120-kDa major surface glycoprotein (MSG) of rat-derived Pneumocystis carinii were analyzed in vitro. Specific cytokines elicited by the T-cell response to the MSG were also identified. MSG was purified from rat-derived P. carinii by three different techniques: lectin affinity chromatography, sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by electroelution, and size-exclusion high-performance liquid chromatography. The cell-mediated immunity of spleen cells isolated from Lewis rats with and without natural exposure to P. carinii to the purified MSG was studied. Exposure to P. carinii was monitored by the presence or absence of serum antibodies to P. carinii antigens by Western blotting (immunoblotting). A T-cell proliferative response to the MSG was identified only with spleen cells isolated from rats exposed to P. carinii and peaked at 4 days. Flow cytometric analysis revealed that the percentage of CD4 cells was significantly increased during the proliferative response to MSG. MSG also elicited secretion of tumor necrosis factor alpha, interleukin-1, and interleukin-2, with peak activity of these cytokines occurring after 12, 24, and 48 h, respectively, of culture. These findings suggest that MSG is important in host T-cell recognition of and immune response to P. carinii by recruitment of inflammatory cells and cytokine production.

Animals↗

PubMed1988

A comparison of cyclobenzaprine and placebo in the management of fibrositis. A double-blind controlled study.

The efficacy of cyclobenzaprine (Flexeril), as compared with placebo, was tested in a 12-week, double-blind, controlled trial of 120 patients with fibrositis. Of the patients who received placebo, 52% dropped out due to lack of efficacy of the drug, compared with 16% of patients taking cyclobenzaprine. The dropout rate due to adverse reactions was similar in the 2 groups. Patients taking cyclobenzaprine experienced a significant decrease in the severity of pain and a significant increase in the quality of sleep. There was a trend toward improvement in the symptoms of fatigue, but morning stiffness was not alleviated. These improvements in symptoms were associated with a significant reduction in the total number of tender points and in muscle tightness. Our findings indicate that cyclobenzaprine is a useful adjunct in treating patients with the fibrositis syndrome.

Adult↗

PubMed1988

Patient outcome following inpatient vs outpatient treatment of rheumatoid arthritis.

To assess the short and longterm efficacy of intensive inpatient treatment of active rheumatoid arthritis (RA), 16 patients, the test group, admitted to a hospital based rheumatic disease unit (mean length of stay 12.4 days) were studied, using clinical and laboratory variables. The comparison group was similarly evaluated, using 10 outpatients with active RA to whom hospitalization was recommended, but refused by the patients. Both groups were studied intensively over a 12-week period. In addition, a 2-year followup was performed on 12 test group inpatients and 8 comparison group outpatients, using the same variables plus a functional status questionnaire. Health care costs were determined for both groups and corrected for a 1985 dollar value. The test group showed significant improvement in morning stiffness, pain, and joint score, whereas the comparison group improved only in pain score during the initial 12-week period. At 2 years, the test group and the comparison group showed significant improvement in morning stiffness, pain, grip strength, and joint score. The comparison group initially had a somewhat lower index of disease activity. The test group maintained their initial improvement and none required rehospitalization. Functional status scores were similar for both groups. Health care costs were initially higher for the test group ($5,065); followup care cost for the test group was $99 less/year than the comparison group over 2 years. Hospitalization on a rheumatic disease unit brought about prompt, sustained improvement in 2 weeks which required nearly 2 years to achieve in the comparison group. Such hospitalization of uncomplicated RA seems warranted to decrease disability and increase the quality of life.

Adrenal Cortex Hormones↗

PubMed1987