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Biomedical subjects

M Kahan

Publications and source records attributed to M Kahan.

At least 19 recordsLinked to original sources
PubMed2000

Identification and characterization of a thrombomodulin gene mutation coding for an elongated protein with reduced expression in a kindred with myocardial infarction.

Thrombomodulin is an endothelial cell receptor for thrombin. It functions as a natural anticoagulant by greatly accelerating activation of protein C by thrombin. Using a direct gene screening strategy we identified a frameshift insertion mutation, insT 1689, in the thrombomodulin gene of a patient with myocardial infarction. The mutation predicts an elongated gene product because of substitution of the 12 C-terminal amino acids by 61 abnormal residues. Pedigree analysis showed that the mutation was also likely to have been present in a sibling who had had fatal myocardial infarction. Carriers of the mutant allele express significantly lower amounts of thrombomodulin on the surface of their monocytes detected by flow cytometry and have lower levels of soluble thrombomodulin in plasma. Wild type and the mutant thrombomodulin were expressed in COS-7 cells. Cellular distribution of the expressed proteins was evaluated by immunofluorescence microscopy, which showed reduced cell surface expression and intense juxtanuclear localization of the abnormal protein. This suggests impaired translocation through the endoplasmic reticulum/Golgi apparatus. Cells expressing abnormal thrombomodulin had reduced ability ( approximately 2.5-fold) to accelerate the thrombin mediated activation of protein C. This is the first demonstration of reduced expression arising from a natural thrombomodulin gene mutation. The results provide support for the suggestion that gene mutation of thrombomodulin may be important in the pathogenesis of some cases of occlusive thrombotic disease. (Blood. 2000;95:569-576)

Adult↗
PubMed1996

IL-3 in combination with IL-4, induces the expression of functional CD1 molecules on monocytes.

CD1 molecules have recently been shown to present bacterial antigens to CD4-CD8-TCR alpha beta + T lymphocytes. The expression of CD1 on monocytes can be induced by GM-CSF and is further enhanced by IL-4. GM-CSF and IL-3 receptors share a common chain and often have similar activities; however, only IL-3, but not GM-CSF, can stimulate CD4-CD8-TCR alpha beta + T lymphocytes directly. In this study we show that IL-3, in combination with IL-4, can also induce the expression of CD1 on monocytes to a level comparable to that induced by GM-CSF/IL-4. This induction of CD1 by IL-3 can be suppressed by IL-10. Furthermore, CD1-induced antigen presentation was similar whether CD1 was induced by IL-3/IL-4 or GM-CSF/IL-4. The ability of IL-3 to induce expression of CD1 molecules and to directly stimulate CD4-CD8- alpha beta + TCR T lymphocytes raises interest in the role of this cytokine in the development, differentiation and function of this T cell subset.

Antigens, CD1↗
PubMed1996

Identifying and managing problem drinkers.

Problem drinking is far more common than severe alcohol dependence and is associated with considerable morbidity and health care costs. Whereas patients with alcohol dependence respond best to intensive treatment, one or more brief sessions of physician advice and counseling reduces alcohol consumption among problem drinkers. The two most useful tools to identify problem drinkers are the CAGE and the drinking problem question.

Alcoholism↗
PubMed1996

Opiate-dependent patients receiving methadone. How physicians should manage therapy.

Methadone treatment can reduce illicit drug use, needle sharing, and the social costs and health risks of heroin addiction. It is superior to no treatment, detoxification, or treatment programs lasting less than 3 months. For most patients, the optimal methadone dose is 50 to 120 mg daily. Supervised, random urine drug specimens should be collected at least twice weekly. Long-term counseling is essential and should include information on the risks of needle sharing and on screening for HIV and hepatitis B and C.

Adult↗
PubMed1995

Effectiveness of physician-based interventions with problem drinkers: a review.

OBJECTIVE: To review the results of randomized controlled trials on the effectiveness of brief physician interventions with problem drinkers. DATA SOURCES: The MEDLINE and EMBASE databases were searched for articles published from 1966 and 1972 respectively, with the terms "problem/controlled/responsible/moderate/risk/drink"; "advice/drink"; "physician, nurse, general practitioner"; and "random." Forty-three articles were identified in the EMBASE search and 112 articles in the MEDLINE search. STUDY SELECTION: All trials examining the effectiveness of interventions by physicians in reducing alcohol consumption among problem drinkers attending a health-care facility were reviewed. Trials involving subjects attending an alcohol treatment clinic and those involving interventions delivered solely by nonphysicians were excluded. Eleven trials met the final selection criteria. DATA EXTRACTION: For each article, two of the authors independently assigned a score from 0 to 2 on a number of criteria for validity and generalizability. DATA SYNTHESIS: The four trials with the highest validity scores showed that men in the intervention groups reduced their weekly alcohol consumption by five to seven standard drinks more than the men in the control groups. Results for women were inconsistent. No convincing evidence of declines in alcohol-related morbidity among men or women was found. CONCLUSIONS: The trials support the use of brief interventions by physicians for patients with drinking problems. Although further studies are needed to determine their effect on morbidity and mortality, the public health impact of such interventions is potentially enormous. Further research is needed to determine which patients are best suited for brief interventions, the optimal intensity of treatment and which components of brief interventions are most effective. Research is also needed to establish which strategies are effective in inducing physicians to use brief interventions.

Alcohol Drinking↗
PubMed1995

Differential effects of interleukin-10 on the expression of HLA class II and CD1 molecules induced by granulocyte/macrophage colony-stimulating factor/interleukin-4.

Interleukin (IL)-10 down-regulates HLA class II molecules, whether constitutively expressed or up-regulated by interferon-gamma or IL-4 on monocytes but not on B lymphocytes. In this study we show that IL-10 does not inhibit HLA class II expression induced by the combination granulocyte/macrophage colony-stimulating factor and IL-4 on monocytes, although it simultaneously abrogates the expression of CD1 molecules induced by the same combination of cytokines. CD1 molecules can act as element of genetic restriction for CD4- CD8- T lymphocytes, and the suppression of CD1 expression by IL-10 abolished antigen presentation to CD1-restricted CD4- CD8- T cell receptor-positive T cells. Although HLA class II expression was not down-regulated by IL-10, the antigen specific proliferative response of CD4+ T cells was nevertheless decreased. This was not caused by down-regulation of known co-stimulatory molecules such as B7.1, B7.2 and ICAM-1. IL-10 decreased the antigen specific proliferative response further by directly influencing the T lymphocytes. Our results indicate that IL-10 exerts some of its immunoregulatory functions by differential modulation of antigen presenting molecules, induced by the same combination of cytokines.

Antigen Presentation↗
PubMed1995

Soluble TNF receptor production by activated T lymphocytes: differential effects of acute and chronic exposure to TNF.

Soluble tumour necrosis factor receptors (sTNF-R) are up-regulated at sites of chronic inflammation such as rheumatoid synovial joints. The p75 sTNF-R is the more abundant, suggesting an important role for this TNF inhibitor in regulating TNF bioactivity in vivo. As the precise cellular source of these soluble receptors is not known, we investigated the production and regulation of sTNF-R by T lymphocytes, an abundant cell type in inflammatory infiltrates, which upon activation express high levels of p75 surface receptors. Using panels of T-cell lines and clones expressing high levels of p75 TNF-R, we found that p75 sTNF-R production upon stimulation is a feature common to all subsets of T cells, including cells of the CD4-CD8- double negative phenotype expressing either alpha beta or gamma delta T-cell receptors (TCR). In contrast, levels of p55 sTNF-R were only detected when T cells were stimulated at higher densities and by potent mitogens such as phorbol 12-myristate 13-acetate (PMA). Detailed kinetic analyses revealed that the production of p75 sTNF-R was biphasic, the first phase was activation dependent, occurring in the absence of detectable TNF, while the second phase of p75 sTNF-R production was regulated by cytokines such as TNF. Unlike short-term exposure to TNF which enhances sTNF-R production in vitro and in vivo, prolonged exposure of T lymphocytes to TNF suppressed p75 sTNF-R (but not p55 sTNF-R) production in a dose- and time-dependent fashion. These results suggest that in patients with chronic inflammatory disease, which are exposed to augmented levels of bioactive TNF for prolonged periods, the production of p75 sTNF-R may be impaired.

Clone Cells↗
PubMed1993

The effects of tumor necrosis factor (TNF) derivatives on TNF receptors.

The pleiotropic cytokine TNF has been implicated in the regulation of many immune and inflammatory responses in vivo, and in addition exerts a wide range of effects on target cells in vitro. However, although two cell surface receptors for TNF have been identified, and their cDNAs cloned, the amino acid residues necessary for the biological activity of TNF have not been characterized. We have therefore constructed derivatives of TNF termed 'muteins', in which the first 3 to 7 amino acids of native TNF-alpha have been replaced, using synthetic cDNA expressed in E. coli. In the present study we compare the effects of native TNF-alpha and muteins III, IV, V and VI in several different in vitro systems and in one in vivo model. We observed binding to the p75 TNF receptor on Jijoye Burkitt lymphoma cells with native TNF-alpha and mutein III alone, whereas the p55 TNF receptor on the human epithelioid carcinoma cell line HeLa bound TNF-alpha, mutein III and mutein V. Muteins IV and VI failed to recognize either TNF receptor. WEHI 164 fibrosarcoma cells were killed by muteins III, V and VI. Human umbilical vein endothelial cells responded to native TNF-alpha and to muteins III, IV and V, but not to mutein VI, by increasing the surface expression of ICAM-1 antigen and secretion of the cytokines GM-CSF and IL-6. All four compounds were pro-inflammatory in a mouse in vivo model. The results presented in this report confirm that N-terminal amino acids are critical for both receptor binding and biological activity of TNF-alpha.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Evidence that rapamycin has differential effects of IL-4 function. Multiple IL-4 signaling pathways and implications for in vivo use.

The immunosuppressive drug rapamycin, which inhibits the response of T cells to growth-promoting lymphokines, has been considered to act as a general inhibitor of cytokine action. Our investigations into the effect of rapamycin on human IL-4, a cytokine controlling B and T cell function, show this not to be the case. Unexpectedly, rapamycin actually synergized with IL-4 in both the upregulation of CD23 expression and the down-regulation of the type II (p75) TNF receptor, while in the same B cell line, rapamycin simultaneously inhibited the IL-4-dependent production of TNF alpha and beta. These results raise the possibility that multiple IL-4 signaling pathways may be responsible for the pleiotropic effects of IL-4, and have important implications for both the experimental and possible clinical in vivo use of rapamycin as a selective immunosuppressant.

B-Lymphocytes↗
PubMed1993

Definition of unique traits of human CD4-CD8- alpha beta T cells.

We have studied the nature of human CD4-CD8- (double negative) alpha beta T cells to determine whether they possess unique characteristics which could further differentiate them from conventional CD4+ or CD8+ (single positive) T cells. We observed that double negative TCR alpha beta+ T cells differ from single positive T cells in the following respects: (i) their T cell receptor (TCR) repertoire is different, as revealed by the analysis of 47 clones derived from three individuals and by analysis of peripheral blood lymphocytes (PBL) prior to in vitro manipulation; (ii) their in vivo CD3:TCR expression is lower before in vitro manipulation and expansion; (iii) their direct proliferative response to IL-3, which is not mediated by secondary release of other T cell growth factors. These characteristics have also been recently ascribed to murine double negative alpha beta T cells, which develop extrathymically and are considered to be a distinct T cell lineage. Our data suggest that, like their murine counterparts, human double negative alpha beta T cells may represent a distinct T cell lineage which might develop extrathymically.

CD3 Complex↗
PubMed1993

Multiple personality in eating disorder patients.

Although the overlap between childhood sexual and physical abuse and eating disorders is well known, little work has been done on the sequelae of childhood trauma in eating disorder patients. Dissociative phenomena are common in adult survivors of childhood abuse, with multiple personality disorder (MPD) being the most extreme form of dissociative disorder. We describe two women who presented for inpatient treatment of eating disorders who were subsequently found to have MPD. Because the eating pathology in these patients contained atypical features related to the MPD process, uncovering MPD was critical in the treatment of their eating behavior. MPD should be considered in any atypical or treatment-resistant eating disorder patient.

Adult↗
PubMed1993

Expression of the identical V beta gene in human T-cell clones does not confer the same pattern of responsiveness to bacterial enterotoxins.

Superantigens are the most potent T-cell mitogens so far described, and are believed to activate virtually all the T lymphocytes bearing the appropriate V beta segment in their T-cell receptor (TcR). In order to determine whether the expression of the identical V beta gene confers the same pattern of responsiveness to bacterial superantigens, we have established a panel of 20 untransformed human T-cell clones expressing the V beta 6.7a gene in their TcR. The V beta usage was defined by immunostaining, using the V beta 6.7a-specific monoclonal antibody (mAb) OT145, and confirmed by DNA sequencing of the beta-chain. Although all the clones analysed expressed the same V beta gene, they had disparate patterns of proliferation to challenge with a panel of bacterial enterotoxins. This study demonstrates that the mere expression of the same V beta region by T lymphocytes does not grant an indistinguishable responsiveness to bacterial superantigens. Thus other, as yet undefined, T-lymphocyte components play a key role in the process of T-cell activation induced by bacterial superantigens, influencing the effects mediated by exogenous superantigens on human T cells.

Amino Acid Sequence↗
PubMed1991

Regulatory interactions among autologous T cell clones. Human bifunctional T cell clones regulate the activity of an autologous T cell clone.

In contrast to the ease of cloning and characterizing, at the molecular level, helper and cytotoxic T cells, suppressor T cells remain an enigma, and their existence as discrete entities is being increasingly challenged. Here we review evidence that CD4+ regulatory clones, capable of expressing both helper and suppressor functions, may account for much of the suppressor function. It is suggested that a single T cell clone, depending on the signals it receives from its environment, may release either helper or suppressor cytokines. Studying such clones under defined conditions (providing suppressor signals), may preclude detection of their helper capacity. Since some therapeutic approaches in various human diseases are based on the manipulation of helper and suppressor functions, the question whether committed suppressor cells exist has important practical implications in medicine.

Clone Cells↗
PubMed1991

Preferential expression of V beta 6.7 domain on human peripheral CD4+ T cells. Implication for positive selection of T cells in man.

The peripheral T cell receptor repertoire is mainly controlled by the processes of positive and negative selection occurring in the thymus. Studies in normal or transgenic mice have provided compelling evidence for both negative and positive selection. Negative selection is characterized by partial or total disappearance from the periphery of T cells expressing certain C beta regions, which are normally present in the thymus. Positive selection is chiefly characterized, in the periphery, by an imbalanced ratio between CD4+ and CD8+ T cells expressing a given V domain. To date little information concerning positive and negative selection has been available in man. We studied the distribution of 4 V beta domains on CD4+ and CD8+ peripheral T cells of 34 healthy individuals with a wide age-range (0-96 years). One of the V beta domain studied, V beta 6.7, is preferentially expressed on CD4+ compared to CD8+ T cells (p greater than 0.001). No significant differences were observed using the other V beta domain-specific monoclonal antibodies (V beta 5.2-5.3, 8 or 12). These results provide evidence that a process of thymic education, similar to that described in murine animal models, may also take place in man.

Adult↗
PubMed1990

Interactions between autologous T cell clones.

A human CD4 clone (Mx9/9) using the V beta 8 receptor was used as antigen to generate autologous clones (termed anti-Mx9/9 clones) which proliferate in response to this clone, but not other autologous clones. This was used as an experimental model to explore the specific interactions between autologous T cells. Anti-HLA-DR monoclonal antibodies inhibited the response of the anti-Mx9/9 clones, suggesting that these clones recognize their target antigen in association with HLA-DR. Because of the specificity of the anti-Mx9/9 clones for the initiating clone (Mx9/9), but not any other autologous V beta 8- or V beta 8+ CD4 clones, the target antigen seems to be part of the T cell receptor, but not V beta 8 itself. However, the anti-Mx9/9 clones responded also to the autologous EBV line, and thus the target antigen is not known. The regulatory activity of the anti-Mx9/9 clones was assayed by coculture with their target clone. A variety of responses were seen, both inhibitory and stimulatory, which varied depending on the "conditions" of the T cell used. These results suggest that T cells interact in a complex network, perhaps as complex as the regulatory interactions between antibody molecules and B cells.

Antibodies, Monoclonal↗
PubMed1990

Specific interactions between a human CD4+ clone and autologous CD4+ bifunctional immunoregulatory clones.

The cellular communications between a human CD4+ clone and autologous CD4+ clones induced with the first clone are described. The autoreactive clones proliferated after stimulation with the inducer clone, but not after stimulation with autologous clones expressing irrelevant specificities. The inducer clone markedly lost its ability to interact with the autoreactive clones after the modulation of its T-cell receptor. The proliferation of the autoreactive clones stimulated with the inducer clone was blocked by anti-DR monoclonal antibody. Collectively, these findings indicate that the autoreactive clones recognize idiotypic-like determinants on the receptor of the inducer clone in conjunction with DR antigen. The regulatory activity of the autoreactive clones was assayed by co-cultivation with their target inducer clone. The autoreactive clones were not committed to a single program, they could either suppress or enhance the proliferation of the target cells depending on the state of activation of the target cells. Activated target cells were suppressed whereas non-activated cells were enhanced. It is predicted that antagonistic cytokines released from the autoreactive clones exert differential effects on the target clone.

Animals↗
PubMed1990

CD5 (Ly-1)-negative, conventional splenic B cells make a substantial contribution to the bromelain plaque-forming cell response in CBA and BW mice.

CD5 (Ly-1) B cells are a minor subpopulation in mouse spleen and are thought to be responsible for the production of natural autoantibodies to bromelain-treated autologous erythrocytes (Br-RBC). Here it is shown that substantial numbers of conventional, CD5-negative, splenic B cells also secrete these antibodies in CBA and (NZB x NZW)F1 mice, whereas in NZB and BALB/c mice they are all produced by the CD5 B-cell population. However, stimulation with bacterial lipopolysaccharide in vivo preferentially activates the CD5 B-cell group to anti-Br-RBC antibody secretion.

Animals↗