Biomedical subjects

P R Beatty

Publications and source records attributed to P R Beatty.

11 recordsLinked to original sources

PubMed1998

CD30 expression identifies a functional alloreactive human T-lymphocyte subset.

BACKGROUND: CD30 is a member of the tumor necrosis factor/nerve growth factor receptor family and has been proposed as a marker of specific cytokine-producing subsets in humans. Previous studies have examined the expression of CD30 on established T helper type 1 and T helper type 2 cell clones and the function of CD30+ cells after mitogenic stimulation. In this study, we examined the development and function of CD30+ T cells generated in response to alloantigen. METHODS: Primary one-way mixed lymphocyte reactions were established, and the expression of CD30 on T lymphocytes was determined by immunofluorescence and flow cytometry. Fluorescence-activated cell sorting was utilized to define the cytokine profile of alloactivated CD30+ cells after restimulation with anti-CD3 monoclonal antibodies or alloantigen. The effect of cyclosporine on the development of CD30+ cells, and on cytokines produced by CD30+ T lymphocytes, in response to alloantigen was determined. RESULTS: CD30+ T lymphocytes could be detected on day 2 of mixed lymphocyte reactions and continued to increase in number and proportion through day 6. Both CD4 and CD8 T cells expressed CD30 after primary alloantigenic stimulation. CD30+ T cells are a subset of alloactivated T cells and are the major source of interferon-gamma and interleukin-5 produced in response to alloantigen. Cyclosporine partially, but not completely, inhibits the development of CD30+ cells, and has a greater effect on interferon-gamma production than on interleukin-5 production. CONCLUSIONS: CD30+ T lymphocytes may constitute an important immunoregulatory subset in human allograft rejection.

CD4-Positive T-Lymphocytes↗

PubMed1998

Effect of cyclosporine and tacrolimus on the growth of Epstein-Barr virus-transformed B-cell lines.

BACKGROUND: Transplant patients receiving immunosuppressive drugs are at increased risk for Epstein-Barr virus (EBV)-associated disorders including posttransplant lymphoproliferative disorder. The function of T lymphocytes, which are critical to preventing the expansion of EBV-infected B cells, is inhibited by immunosuppressive drugs. The purpose of this study was to determine whether immunosuppressive drugs have direct effects on EBV-infected B cells. METHODS: The growth and proliferation of EBV-infected spontaneous lymphoblastoid cell lines (SLCLs), cultured in the presence or absence of cyclosporine (CsA) and tacrolimus (TAC), were measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and [3H]thymidine incorporation assays. The effect of CsA and TAC on the viability of SLCLs was determined by cell counts with trypan blue. Apoptosis of SLCLs was induced with an anti-Fas agonist monoclonal antibody in the presence or absence of CsA and TAC and measured by flow cytometry after terminal deoxynucleotidyl transferase end-labeling and propidium iodide staining. RESULTS: CsA and TAC, but not sirolimus, increased the growth of SLCLs. The increased growth in the presence of CsA and TAC was attributable to enhanced cell viability and not increased cell division of SLCLs. In addition, CsA and TAC inhibited Fas-mediated apoptosis of SLCLs. CONCLUSIONS: CsA and TAC enhance the survival of EBV-transformed B-cell lines. CsA and TAC promote or augment SLCL growth through protection from cell death but do not affect cell division. The inhibition of cell death by CsA and TAC may contribute to the expansion of EBV-infected cells in immunosuppressed individuals.

B-Lymphocytes↗

PubMed1998

Human hepatocytes produce an isoform of FAS that inhibits apoptosis.

BACKGROUND: Fas (Apo-1/CD95), a member of the tumor necrosis factor receptor family, can mediate apoptosis when engaged by its ligand or by anti-Fas antibody. Fas is expressed by cells of the immune system and by some nonlymphoid tissues. Numerous studies have suggested that the Fas pathway may play a role in the rejection of allografts. Functional, soluble forms of the Fas receptor are produced by activated peripheral blood mononuclear cells and some transformed cell lines. The purpose of this study was to determine if soluble variants of Fas are produced in the liver and to determine if blockade of the Fas pathway, by liver-derived soluble Fas, inhibits Fas-mediated apoptosis. METHODS: Liver and purified hepatocyte specimens were analyzed for Fas transcripts by reverse transcriptase-polymerase chain reaction with primers that span the transmembrane region of the molecule. Bile and cell lysates were analyzed for soluble Fas by specific enzyme-linked immunosorbent assay. Lysates were prepared from normal liver and hepatocytes and utilized to block Fas-mediated apoptosis of Jurkat cells as determined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling and flow cytometry. RESULTS: A variant form of Fas is abundantly expressed in normal liver and purified hepatocytes. This variant form of Fas is expressed in all normal liver specimens but only in half of the liver specimens obtained during allograft rejection. The levels of soluble Fas diminish in patients undergoing liver allograft rejection in contrast to patients with stable grafts. Importantly, a soluble form of Fas is produced in the liver by hepatocytes and can specifically inhibit Fas-mediated apoptosis. CONCLUSION: These data raise the possibility that soluble Fas, produced by hepatocytes, may influence the immune response by blocking Fas-mediated apoptosis and, thus, may have a role in liver transplantation.

Apoptosis↗

PubMed1997

Involvement of IL-10 in the autonomous growth of EBV-transformed B cell lines.

Immunocompromised individuals have an increased incidence of EBV-associated B cell lymphomas. The growth factors responsible for the unrestrained proliferation of these lymphomas have not yet been determined. In this study, spontaneous lymphoblastoid cell lines (SLCL) were derived without the addition of growth factors or virus from four patients with EBV-associated lymphoproliferative disorder. These cell lines were EBV transformed in vivo, and infection was verified through amplification of the viral gp220 gene. SLCL have an activated B cell phenotype (CD19+, CD21+, CD23+, CD38+, and CD40+) and produce IL-6, IL-10, TNF-alpha, and lymphotoxin-alpha. To determine whether these cytokines contribute to autonomous growth, neutralizing Abs for IL-10, IL-6, and TNF-alpha, a soluble TNFR:Fc fusion protein, and soluble IL-10R were used. These experiments established that, of the cytokines produced by SLCL, only IL-10 is an autocrine factor. IL-10 was produced by the majority of cells within each SLCL, and IL-10 secretion was concomitant with SLCL growth. Our findings demonstrate that IL-10 is utilized in the autonomous growth of EBV-related lymphomas and may be crucial in the development of lymphoproliferative disorder.

B-Lymphocytes↗

PubMed1997

Cross-reactive cytotoxic T-lymphocyte-mediated lysis of Chlamydia trachomatis- and Chlamydia psittaci-infected cells.

Cells infected with Chlamydia trachomatis are lysed by CD8+ T cells in vitro. The ability of C. trachomatis-elicited spleen cells to lyse target cells infected with other chlamydial strains was determined by measuring lysis by immune spleen cells of targets infected with three strains of C. trachomatis and two strains of C. psittaci. C. trachomatis (lymphogranuloma venereum [LGV])-elicited immune murine spleen cells lysed target cells infected with other C. trachomatis serovars, although with lower sensitivity than they lysed LGV-infected target cells. Additionally, target cells infected with C. psittaci were lysed by C. trachomatis-elicited immune spleen cells. Notably, C. psittaci-infected cells were lysed with greater efficiency than were cells infected with the C. trachomatis strain used to elicit the immune spleen cells. The lysis of C. psittaci-infected cells was characterized further and could be only partially accounted for by CD8+ T-cell-mediated lysis, the remaining lysis being due to an antigen-nonspecific component. These results indicate that mechanisms of immunologically mediated lysis differ between C. trachomatis- and C. psittaci-infected cells. This has important implications for the interpretation of results obtained with C. psittaci models of infection and immune resolution, particularly as they may be extrapolated to C. trachomatis.

Animals↗

PubMed1996

Cytotoxic-T-lymphocyte-mediated cytolysis of L cells persistently infected with Chlamydia spp.

Persistent chlamydial infections have been proposed as a means whereby chlamydiae evade immune resolution of infection. Such a mechanism would require evasion not only of the humoral immune responses but also of cell-mediated immune responses. We hypothesized that if such a mechanism is important, persistently infected cells should not be recognized by cytotoxic T cells. Persistent infections were simulated in vitro by treatment of Chlamydia trachomatis- or Chlamydia psittaci-infected cells with gamma interferon (IFN-gamma), penicillin, or tryptophan depletion. Cultures were examined for induction of a chlamydial stress response (measured by transcription of groesl RNA) and for the effects on viability, infectivity, morphology, and immune recognition. Although both IFN-gamma and penicillin induced aberrant chlamydial morphology and growth, we did not find evidence that these treatments elicited a classical stress response. In addition, T-cell-mediated lysis of Chlamydia-infected target cells treated with IFN-gamma or penicillin or grown in tryptophan-deficient media was examined. The immune cell-mediated lysis of these treated infected cells demonstrated that despite the effects of these compounds on chlamydial growth and development, the infected cells continued to be efficiently recognized and killed by cytotoxic T cells. Thus, it seems unlikely that these in vitro models of persistence represent functional mechanisms to evade immune clearance.

Base Sequence↗

PubMed1994

CD8+ T lymphocyte-mediated lysis of Chlamydia-infected L cells using an endogenous antigen pathway.

Intracellular bacterial pathogens have evolved to either grow in the nutrient-rich cytoplasm or remain sequestered within a vacuole. One potentially important selective advantage for growth within a vacuole may be evasion of cell-mediated detection and cytolysis. To address this question we used the endosomally confined bacterium Chlamydia trachomatis, which naturally infects epithelial cells, to examine CTL-mediated lysis of nonphagocytic cells. CTL-mediated lysis of infected target cells was detected, although the increased expression of ICAM-1 by transfection was required. The elimination of CD8+ T cells or addition of brefeldin A or cycloheximide eliminated specific cytolysis, whereas conversely, treatment with chloroquine or ammonium chloride had only minor effects. These results implicate endogenous Ag processing for Chlamydia-specific cytolysis. This work demonstrates CTL-mediated lysis of cells infected with an intracellular bacterium that inhibits lysosomal fusion and is confined to an endosomal vacuole.

Animals↗

PubMed1992

Identification of Chlamydia trachomatis antigens by use of murine T-cell lines.

Chlamydia-specific short-term T-cell lines were used in conjunction with immunoblot techniques to examine Chlamydia trachomatis proteins for T-cell-stimulatory activity. This study was undertaken because of the known role of T cells in the resolution and pathogenesis of chlamydial infections. Therefore, determination of which chlamydial proteins are T-cell antigens and whether they evoke protective immunity or contribute to immunopathology is crucial. Immune lymph node cells were stimulated with whole chlamydial organism (elementary body) to derive predominantly CD4+ T-cell lines. Proteins from the elementary body and the outer membrane and cloned proteins were examined for antigenicity with these T-cell lines in a proliferation assay. Although a majority of the elementary body protein fractions were positive in this assay, only four of the outer membrane fractions were stimulatory. The cloned major outer membrane protein and outer membrane protein 2 were stimulatory in the assay and may account for the reactivity in three of the four positive outer membrane fractions. The C. trachomatis heat shock protein 60, examined because of its putative role in causing delayed-type hypersensitivity, was found to stimulate the CD4+ T cells. This approach with short-term T-cell lines with polyclonal reactivity was sensitive and specific in identifying chlamydial proteins as T-cell antigens.

Animals↗

PubMed1992

Immune specificity of murine T-cell lines to the major outer membrane protein of Chlamydia trachomatis.

The antigenically variant Chlamydia trachomatis major outer membrane protein (MOMP) is a target of antibody-mediated neutralization in vitro, and it is an important protein for designing a subunit vaccine. Knowledge of MOMP T-cell determinants will be essential to elicit rapid and strong immune responses following an encounter with infectious organisms. C. trachomatis-specific T-cell lines were derived from MOMP-immunized BALB/c mice and selected with intact organisms. We used these short-term T-cell lines to identify determinants of MOMP that could be recognized by T cells following processing of the intact organism. T-cell line proliferation in response to overlapping MOMP peptides showed that only a peptide encompassing the third variable segment (VS3) elicited a strong proliferative response. We further mapped determinants within the VS3 peptide and found that a sequence-conserved portion of the VS3 peptide elicited T-cell proliferation of T-cell lines from BALB/c mice. Thus, unlike the response to several MOMP peptides with unselected T cells, development of short-term T-cell lines with intact organisms restricted the repertoire of antigens capable of being recognized by MOMP-specific T cells.

Amino Acid Sequence↗

PubMed1990

Cysteine-rich outer membrane proteins of Chlamydia trachomatis display compensatory sequence changes between biovariants.

Two cysteine-rich proteins of Chlamydia trachomatis are essential structural components of the unique outer membrane of the infectious elementary body. These 58,000 (outer membrane protein 2; OMP2) and 15,000 (OMP3) proteins also differ structurally and chemically between biovariants that differ in invasive capability. We have identified the gene for OMP3 and sequenced both trachoma and lymphogranuloma venereum (LGV) omp3 genes. We have previously sequenced omp2 from the LGV biovar and now describe the omp2 sequence for a trachoma biovariant. Amino acid sequence differences between biovariants were few but, significantly, these changes have altered the charge of both OMP2 and OMP3 such that the net charge of each protein differs between biovariants. These compensatory charge alterations have implications for the outer membrane organization of these proteins. In addition, examination of the OMP3 sequence suggests that OMP3 may be a lipoprotein.

Amino Acid Sequence↗

PubMed1987

Attitudes and perceptions of nursing students toward preparation for interdisciplinary health care teams.

Using a modification of the Snyder's Health Care Team Questionnaire, the author conducted a study pertaining to attitudes of undergraduate nursing students toward health care teams, and perception of curriculum content on health care teams. The study design involved a random sample of 126 associate degree programmes and 122 baccalaureate degree programmes representing 14 southern states; 588 senior nursing students responded to the questionnaire. Analysis of the data collected suggested differences in attitudes of students. In addition, the data indicated that differences did exist between programmes on specific health care team concepts taught and settings chosen for clinical experiences. Differences were also detected between programmes in perception of readiness of the students to participate as health care team members, and the number of courses taught on health care teams. Data from an Interdisciplinary Health Care Team Questionnaire were analysed using univariate analysis of variance (ANOVA) with the total scale representing attitude as the dependent variable. The statistical design was a mixed model ANOVA with the type of nursing programme as the fixed factor with two levels: 'Associate Degree' and 'Baccalaureate Degree'. The School of Nursing was the random factor nested within programme type.

Attitude of Health Personnel↗