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At least 865 records · Page 48Linked to original sources
PubMed1980

Functional analysis of human T cell subsets defined by monoclonal antibodies. I. Collaborative T-T interactions in the immunoregulation of B cell differentiation.

T-B and T-T interactions involved in the regulation of PWM-triggered human B cell differentiation were studied in vitro. Functionally distinct human T cell subsets were isolated by C-mediated lysis by using the monoclonal antibodies OKT4 and OKT8. Graded numbers of either untreated or irradiated T cell subsets were added to autologous B cells, and total antibody synthesis was measured after 5 to 6 days of culture by using a highly sensitive reverse hemolytic plaque assay. The data indicate that a) the helper activity that is exclusively contained within the OKT4+ population is radiosensitive. Only at high T/B ratios can this radiosensitivity be overcome; b) the OKT8+ population contains radiosensitive cells important in suppressing B cell differentiation, and c) the suppression induced with OKT8+ cells requires the presence of radiosensitive OKT4+ cells. Thus, OKT8+ cells added to cultures containing B cells and irradiated OKT4+ cells do not suppress the PFC response. Addition of unirradiated OKT4+ cells to these cultures permits reexpression of suppression by OKT8+ cells. It is concluded that two radiosensitive cells, one within the OKT4+ population and the other within the OKT8+ population, collaborate to induce suppression. Possible mechanisms for this suppressive interaction including induction of suppressor precursor cells within the OKT4+ population or inhibition of OKT4+ helper cells by OKT8+ cells are discussed.

Antibodies↗
PubMed1981

Functional analysis of human T cell subsets defined by monoclonal antibodies. II. Collaborative T-T interactions in the generation of TNP-altered-self-reactive cytotoxic T lymphocytes.

In previous reports we have demonstrated that human T cells, responding to soluble and alloantigens, release helper factor(s) that amplify primary in vitro hapten-altered-self-reactive CTL responses. In the present studies, we have employed complement-fixing monoclonal antibodies (OKT4 and OKT8) that recognize functionally distinct human T cell subsets to investigate the role of T-T interaction in the generation of these killer cells. In all experiments, purified OKT4+ responder T cells were deficient in cytotoxic activity, whereas responder populations containing OKT8+ T cells generated substantial cytotoxicity; demonstrating that TNP-altered-self-reactive CTL precursors are contained within the OKT8+ T cell subset. Further, optimal cytotoxic responses were obtained from responder populations containing both OKT4+ and OKT8+ T cells, suggesting that cooperative interaction between these subsets may result in an amplification of killer cell activity. This interpretation was supported by the following observations: (1) the amplifying effect of soluble antigen required the presence of both OKT4+ and OKT8+ responders; (2) during MLC, OKT4+ but not OKT8+ responder T cells generate helper factor(s) that amplify TNP-altered-self-reactive CTL responses; (3) helper factor(s) bypass the requirement for direct OKT4-OKT8 T cell interaction, triggering a CTL response that is proportional to the percentage of OKT8+ T cells present within the responder population. In additional studies, we determined that the TNP-altered-self-reactive effector CTL maintain the OKT3+, OKT4-, OKT8+ surface phenotype displayed by the CTL precursor.

Antibodies↗
PubMed1995

Duplication of the extracranial internal carotid artery.

We describe a case of duplication of the left internal carotid artery from a point 1 cm distal to the origin to the proximal petrous segment where the vessel reunites. Duplication and fenestration of the internal carotid artery are discussed. A review of embryologic development is presented. Identification of these entities is important, especially in patients who require surgical intervention involving the internal carotid artery.

Angiography, Digital Subtraction↗
PubMed1994

CD40 molecules induce down-modulation and endocytosis of T cell surface T cell-B cell activating molecule/CD40-L. Potential role in regulating helper effector function.

The T-BAM/CD40-L molecule on CD4+ T cells interacts with B cell CD40 molecules to deliver contact-dependent signals that drive B cell activation and Ig secretion. Cell surface T-BAM/CD40-L expression is transient and may be closely regulated in order to limit the activation and clonal selection of noncognate B cells. We demonstrate that B cells, but not non-B cells, rapidly and specifically down-modulate surface T-BAM/CD40-L expression in a contact-dependent and temperature-sensitive manner that renders T cells unable to activate resting bystander B cells. Because the ability to down-modulate T-BAM/CD40-L correlated with CD40 expression, the role of CD40 molecules in down-modulating its ligand was directly assessed. Anti-CD40 mAb, but not control mAb, block B cell-induced T-BAM/CD40-L down-modulation. Furthermore, CD40+ nonlymphoid transfectants specifically down-modulate surface T-BAM/CD40-L expression. B cells induce T-BAM/CD40-L internalization into cytoplasmic compartments in a process that is inhibited by cytochalasin B. Pretreatment of activated T cells with lysosomotropic agents does not affect CD40-induced down-modulation of surface T-BAM/CD40-L but results in a marked accumulation of T-BAM/CD40-L in cytoplasmic vesicles. Together, these studies strongly suggest that CD40 induced T-BAM/CD40-L down-modulation occurs, in part, by receptor-mediated endocytosis followed by lysosomal degradation and may represent a mechanism to regulate CD4+ T cell helper effector functions.

Amino Acid Sequence↗
PubMed1995

Opposing roles of CD95 (Fas/APO-1) and CD40 in the death and rescue of human low density tonsillar B cells.

The regulation of B cell death plays roles in the selection of Ag-specific B cells in humoral immune responses, controlling B cell homeostasis and perhaps limiting transformation. The present work addresses whether CD95 induces tonsillar B cells to undergo apoptosis and, if so, whether contact-dependent CD40-L:CD40 signaling can rescue tonsillar B cells from CD95-induced apoptosis. CD95 triggering by anti-CD95 mAb (APO-1) was studied in human tonsillar B cell populations that were separated by density centrifugation into fractions enriched for either low density, CD38+ B cells or high density, resting B cells. Low density tonsillar B cells express CD95 and undergo anti-CD95-mediated apoptosis by analysis of cellular morphology or DNA fragmentation by TUNEL assay. The induction of apoptosis in low density tonsillar B cells by anti-CD95 mAb is inhibited by CD40 signals provided by stably transfected CD40-L+ 293 cells, but not by control transfected 293 cells (expressing CD8). In addition, the rescuing effect of CD40-L+ cells is inhibited specifically by anti-CD40-L (mAb 5c8). The counteracting effects of CD95 and CD40 signaling were also studied in Ramos 2G6, a homogeneous B cell tumor line of germinal center phenotype that expresses CD95 and CD40. Similar to the behavior of low density tonsillar B cells, Ramos 2G6 undergoes anti-CD95-mediated apoptosis, which is prevented by CD40-mediated rescue. These data show that CD95 induces apoptosis in low density tonsillar B cells and that CD40-L:CD40 interactions rescue low density tonsillar B cells or the B cell tumor Ramos 2G6 from CD95-induced apoptosis, and suggest roles for CD95 and CD40 in B cell death and selection, respectively.

Apoptosis↗
PubMed1994

T-BAM/CD40-L on helper T lymphocytes augments lymphokine-induced B cell Ig isotype switch recombination and rescues B cells from programmed cell death.

An important component of T cell help for B lymphocyte differentiation is the contact-dependent signaling mediated by the T cell-B cell activating molecule (T-BAM/CD40-L), an activation-induced surface membrane protein on CD4+ T helper cells in lymphoid follicles that interacts with the B cell surface molecule, CD40. The present study dissects the roles of T-BAM/CD40-L in helper function by means of a neutralizing anti-T-BAM/CD40-L mAb (5c8), a T-BAM/CD40-L-expressing T cell tumor subclone (Jurkat D1.1), and a T-BAM/CD40-L-responsive IgM+ B cell tumor of germinal center origin (RAMOS 266). Like activated T cells, D1.1 cells induce B cells to synthesize IgG, IgA, and IgE in a process that is specifically inhibited by the mAb 5c8. Although rIL-4 alone, but not Jurkat D1.1, induces IgH C gamma mRNA transcripts in RAMOS 266, the T-BAM/CD40-L molecule on D1.1 acts on rIL-4-primed RAMOS B cells to augment expression of C gamma transcripts. In addition, IgG+ RAMOS 266 clones were expanded from D1.1- and rIL-4-stimulated cultures that had undergone deletional IgH isotype switch recombination events. Furthermore, T-BAM/CD40-L signals delivered by the D1.1 clone dramatically rescue RAMOS 266 from mAb anti-IgM-induced apoptosis. Taken together, these data support the idea that T-BAM/CD40-L plays important roles in inducing Ig isotype switch recombination and the clonal selection of isotype-switched B cells.

Animals↗
PubMed1994

Phenotypic and functional characterization of T-BAM (CD40 ligand)+ T-cell non-Hodgkin's lymphoma.

The precise mechanisms regulating T-helper function have been intensively investigated. We and others have recently identified a new T-cell-B-cell-activating molecule called T-BAM that directs B-cell differentiation by interacting with the CD40 molecule on B cells. Using a specific monoclonal antibody against T-BAM (5C8), we have previously shown that T-BAM expressing T cells are predominantly CD4+CD8- and in normal lymphoid tissue have a unique distribution. However, no information has been obtained regarding the phenotype and functional properties of human neoplastic T cells. Therefore, we investigated T-BAM expression immunohistochemically in 87 well-characterized T-cell non-Hodgkin's lymphomas and lymphoid leukemias (LL). We found that 21/81 neoplasms expressed detectable T-BAM and these positive tumors belong almost exclusively to the CD4+CD8- subtype. In addition, to determine whether T-BAM expression could be induced on T-BAM-LL cells, we activated T-BAM-LLs in vitro and showed that T-BAM could be upregulated only in CD4+CD8- tumors. Our studies clearly show that T-BAM is constitutively expressed in a large number of T-cell neoplasms with a relative mature phenotype (CD4+CD8-) and that only CD4+ neoplastic T cells can be induced in vitro to express this molecule. Additional studies are necessary to identify the biologic significance of T-BAM expression and its potential and clinical implications.

CD4-Positive T-Lymphocytes↗
PubMed1994

CD40 ligand (CD40L) expression and B cell function in agammaglobulinemia with normal or elevated levels of IgM (HIM). Comparison of X-linked, autosomal recessive, and non-X-linked forms of the disease, and obligate carriers.

Hyper-IgM syndrome is a rare immunodeficiency characterized by low or absent IgG, IgA, and IgE with normal or elevated levels of IgM. It can occur as an acquired or familial disorder with either X-linked or autosomal modes of inheritance. The X-linked form (HIGM1) is a result of mutations in the CD40 ligand (CD40L) gene, but the defect in non-X-linked forms of the disease (HIM) has not been determined. We show here that CD40L expression on activated T cells from non-X-linked patients can be detected by CD40Fc, 5c8 Mab, and anti-TRAP, whereas activated T cells from HIGM1 patients either had no detectable CD40L (Type I), or stained with anti-TRAP but not CD40Fc or 5c8 (Type II). Activated T cells from obligate carriers varied from low to normal expression of CD40L. B cells from HIGM1 and non-X-linked HIM patients proliferated in response to CD40L. Costimulation of B cells from HIGM1, from sporadic HIM, or from non-X-linked HIM patients with CD40L plus IL-2 resulted in some IgM production, but no significant IgG or IgA. Costimulation with CD40L plus IL-10 resulted in significant IgG and/or IgA secretion by B cells from some HIGM1 patients, but consistently failed to stimulate IgG or IgA secretion by B cells from non-X-linked patients. In addition, costimulation with CD40L and IL-4 failed to induce IgE secretion by B cells from one non-X-linked HIM patient, and induced a weak response in another. These results suggest that patients with non-X-linked forms of HIM may have an intrinsic B cell defect preventing heavy chain switching, which is not related to expression of CD40L.

Adolescent↗
PubMed1976

Triggering of human peripheral blood B cells: polyclonal induction and modulation of an in vitro PFC response.

In the present studies we utilized polyclonal activators to analyze the signals required to induce antibody synthesis by subpopulations of human peripheral blood lymphocytes. The in vitro synthesis of antibody directed against sheep erythrocytes was measured by a modification of the Jerne plaque assay. The plaques observed contained central lymphoid cells, could be inhibited by anti-human immunoglobulin, and were strictly dependent on both the addition of complement and viable B lymphocytes actively synthesizing protein. Kinetic analysis showed that the PFC response developed over time during cell culture with peak activity occurring between days 6 and 7. It was found that human peripheral blood B lymphocytes, isolated by Sephadex G-200 anti-Fab column chromatography, were nonspecifically induced by either PWM or soluble products of antigen-activated human T cells to differentiate into PFC. In contrast, unfractionated peripheral blood lymphocytes. Ig- cells isolated from immunoabsorbant columns, and B cells enriched by nylon wool adherence were not triggered to antibody synthesis even in the presence of polyclonal activators. B cells isolated by nylon wool adherence and further fractionated by binding and elution from anti-Fab columns were then readily triggered by PWM to differentiate into PFC. These results suggest that the interaction of human B cells with anti-Fab columns, presumably at the Ig receptor, serves as a signal important in the differentiation events leading to PFC activity. The anti-Fab interaction alone, although critical, was not sufficient to induce the differentiation of precursor cells into PFC since subsequent triggering by antigen-activated T cell supernatants or PWM was required for the development of an optimal PFC response. Additional experimental data demonstrated that the PFC response could be regulated by autologous peripheral Ig- lymphoid cells in vitro. At low concentrations of PWM, Ig- cells consistently augmented the B cell PFC response whereas at high concentrations of PWM, suppression was observed. Depletion of E rosetting cells from the Ig- population eliminated the subset responsible for augmentation but did not eliminate the suppressor cell activity.

Animals↗
PubMed1994

Postoperative evaluation for intracranial recurrence of medulloblastoma: MR findings with gadopentetate dimeglumine.

PURPOSE: To characterize the gadopentetate dimeglumine-enhanced MR features of recurrent medulloblastoma. METHODS: The postsurgical gadopentetate dimeglumine-enhanced MR images of 48 patients (206 head examinations) with prior resection of medulloblastoma were retrospectively evaluated for enhancement in the brain parenchyma, meninges (dura, pia-arachnoid), and ventricles. RESULTS: Nineteen patients had recurrent tumor as determined by clinical course and positive imaging studies. Seventeen patients with recurrent disease had intracranial enhancement predominating in the pia-arachnoid (63%) or as a focal nodular brain lesion (26%). Three of these patients also had intraventricular metastases. None of the clinically healthy patients had these findings. One patient had recurrent tumor presenting within the fourth ventricle. Only 3 of 8 intraventricular lesions observed in the 4 patients initially enhanced with gadopentetate dimeglumine. Another patient with recurrent disease had extensive skeletal metastases without involvement of the central nervous system. Dural enhancement was observed in patients both with (42%) and without (38%) recurrent tumor. CONCLUSION: The MR findings of pia-arachnoidal or focal nodular brain enhancement are highly specific in the diagnosis of recurrent medulloblastoma. Pia-arachnoidal or focal brain enhancement were also the most frequent patterns associated with recurrent tumor. Dural enhancement alone is not a reliable indicator of recurrent medulloblastoma. Not all intraventricular metastases enhance with gadopentetate dimeglumine, and careful evaluation for nonenhancing lesions within the ventricles should be made on postoperative MR examinations.

Adolescent↗
PubMed1994

Compression forces generated by the Huene alignment guide alone.

To enhance the fixation of scaphoid fractures by providing precise alignment and compression at the fracture site, the Huene alignment guide has been used in conjunction with bone screws. In an effort to predict the compressive force generated by the Huene guide alone, these forces were measured with a calibrated, strain-gauge, instrumented device. Three orthopedic surgeons each tested the guide 10 times on one cadaver scaphoid bone specimen. The magnitude of the compressive forces generated ranged from 9.0 to 67.0 N (mean 36.0 +/- 15.0 N). Comparisons of the force measurements among the individuals revealed no significant differences. This wide range of measurements could be attributed to the variability of the ratchet mechanism on the device. Because the Huene alignment guide is used to generate transcaphoid compressive forces, these results demonstrate that it does not yield consistent compression.

Bone Screws↗
PubMed1993

Clostridium perfringens infection of an anterior iliac crest bone graft donor site. A case report.

Postoperative infection of elective surgical wounds with Clostridium species has been linked to gastrointestinal tract lesions. A 55-year-old man with a history of peptic ulcer disease was treated by open reduction and internal fixation with autogeneic cancellous bone grafting from an anterior iliac crest donor site for nonunion of the clavicle. A mild serosanguinous drainage from the Penrose drain site at the iliac crest had ceased on postoperative Day 11; the patient complained of pain and a brownish drainage on postoperative Day 15. The infection was documented with cultures positive for Clostridium perfringens. Aggressive emergent surgical and antibiotic therapy resulted in complete clinical recovery. The wound infection did not advance to severe tissue damage and myonecrosis. This case represents the first reported infection of an iliac crest bone graft site with C. perfringens.

Bone Transplantation↗
PubMed1993

HIV-gp 160-induced T cell-dependent B cell differentiation. Role of T cell-B cell activation molecule and IL-6.

The HIV envelope glycoprotein gp160 has been previously demonstrated to induce differentiation of normal B lymphocytes into Ig-secreting cells; the response is T cell-dependent, and T cells pretreated with gp160 can support B cell differentiation. This study investigates the cell surface molecules and cytokines that play a role in the gp160-induced T-B cell interaction. Utilizing CD4+CD45RO+ cloned T cells as the source of helper cells, we observed that physical contact with B cells is essential for the gp160-induced B cell response; no IgG-secretion occurred if T cells were separated from the B cells by culturing them in Transwell chambers. The expression of T cell-B cell activation molecule, a novel surface molecule associated with T cell activation, was moderately increased by gp160, and antibody to T cell-B cell activation molecule abrogated the gp160-mediated Th cell function. Cell surface molecules LFA-1, ICAM-1, HLA-DR, CD28, and B7 were also involved in the T-B cell interaction since mAb to any of these molecules inhibited the gp160-induced B cell differentiation response. gp160 also induced IL-6R and CD23 molecule expression on B cells when added to cultures of T plus B cells; there was CD23 expression only in cells that formed conjugates with T cells. Paraforamaldehyde-fixed, gp160-pretreated T cells failed to elicit IgG responses in B cells, but did induce CD23 and IL-6R up-regulation on B cells. Addition of exogenous IL-6, but not IL-2 or IL-4, restored the IgG secretion. These findings indicate that the T cell dependence for gp160-induced B cell differentiation responses involves two steps: one requires contact-dependent interaction of several cell surface molecules, and the second requires IL-6 secretion.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1993

Effects of social support and undermining on African American workers' perceptions of coworker and supervisor relationships and psychological well-being.

Although social undermining is a commonly experienced stressor in human services workplaces, it has received little study in contemporary models of social work stress and burnout. Furthermore, African Americans currently make up nearly 25 percent of self-identified social workers in the United States, yet most literature on personnel relationships in human services does not reference this group. Data collected from a national sample of 288 African American members of the National Association of Social Workers were used to investigate the impact of undermining among coworker and supervisor-supervisee relationships. Multiple regression analyses revealed substantial increases in irritability, depression, anxiety, and depersonalization among social workers when social undermining was included in a set of predictor variables (age, gender, and social support). The presence of social support, however, did not diminish the impact of undermining. The authors discuss several practice and training implications of these findings.

Adult↗
PubMed1996

The cementless anatomic medullary locking femoral component: an independent clinical and radiographic assessment.

OBJECTIVE: To review the clinical performance of the anatomic medullary locking (AML) femoral stem in total hip arthroplasty. DESIGN: A clinical and radiographic review. SETTING: A tertiary lower limb joint replacement centre. PATIENTS: Two hundred and twenty-one patients with noninflammatory gonarthrosis. INTERVENTIONS: Two hundred and twenty-seven primary total hip arthroplasties with the noncemented AML component completed by two surgeons. MAIN OUTCOME MEASURES: Independent review by two experienced reviewers of the postoperative Harris hip score, radiographs of component fixation, size and degree of diaphyseal fill. RESULTS: Harris hip score was 84 (range from 43 to 98); component fixation showed bone ingrowth in 41%, stable fixation with fibrous ingrowth in 56% and unstable fixation in 3%; severe thigh pain in 4% of cases correlated with unstable fixation, and there was mild thigh pain in 20% of cases. CONCLUSION: The AML femoral stem performs well in replacement arthroplasty compared with other noncemented stems.

Adult↗