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Biomedical subjects

N Manjunath

Publications and source records attributed to N Manjunath.

At least 37 records · Page 2Linked to original sources
PubMed1998

TCR signaling induces selective exclusion of CD43 from the T cell-antigen-presenting cell contact site.

CD43, a large highly glycosylated molecule, is arguably the most abundant molecule on the surface of T cells. Nevertheless, the function of CD43 remains unclear. Utilizing fluorescence microscopy, we find that CD43 is excluded from the T cell-APC contact site. This exclusion is Ag dependent since optimal CD43 exclusion requires Ag-pulsed APC, and since signaling through CD3, in the absence of any other receptor ligand interactions, can induce the modulation of CD43. These data suggest that CD43 may function as a barrier to nonspecific T cell-APC interactions that is removed as a result of T cell activation. Exclusion from the interaction site is a unique feature of CD43 and not universally found for all large highly glycosylated molecules since CD45 is not excluded. Thus, CD43 may represent a novel regulatory molecule on the T cell surface that can direct T cell interactions by changing its location on the cell surface.

Antigen-Presenting Cells↗
PubMed1998

Negative regulation of T cell homing by CD43.

We report that the cell surface mucin CD43 acts as an anti-adhesin on T lymphocytes. CD43-deficient murine lymphocytes homed significantly more frequently to secondary lymphoid organs than wild-type cells. Intravital microscopy of peripheral lymph node venules revealed that CD43-deficient lymphocytes were twice as likely to tether, roll, and stick than wild-type cells. This effect was due to CD43 interference with the homing receptor, L-selectin, and was most pronounced in venules with low L-selectin ligand density. In vitro, CD43-deficient cells tethered to L-selectin ligands more efficiently and rolled more slowly than wild-type lymphocytes. Thus, CD43 exerts a negative regulatory effect on T cell trafficking by counterbalancing L-selectin-mediated adhesion.

Animals↗
PubMed1998

Regulation of in vitro and in vivo T cell activation by CD43.

Accessory molecule interactions can be critical in determining the outcome of a T cell's encounter with antigen. Cell adhesion proteins may augment T cell responses by facilitating TCR engagement of the antigen-MHC complex, while co-stimulatory molecules may deliver distinct signals that modulate T cell responsiveness. CD43 (leukosialin, sialophorin) has been suggested to influence cell activation by steric hindrance based upon the large size and glycosylation of the protein, as well as the relative abundance of the protein on the cell surface. In this paper we examine both in vitro and in vivo T cell-dependent responses in CD43-deficient mice. We demonstrate that T cells from CD43-deficient mice are hyper-responsive following both in vivo and in vitro activation, and that this is observed in response to not only TCR-CD3-mediated stimulation, but also following receptor-independent activation. This data suggests that mechanisms other than non-specific steric hindrance are important in the regulation of T cell activation by CD43.

Animals↗
PubMed1995

CD43 regulates tyrosine phosphorylation of a 93-kD protein in T lymphocytes.

The leukocyte sialyloglycoprotein CD43 exhibits features of a signal transducing molecule and is thought to be important for T-cell activation and adhesion. However, cellular biochemical events in which CD43 participates remain poorly understood. Here we provide evidence that CD43 regulates tyrosine phosphorylation of a specific substrate in T cells. A 93-kD tyrosine phosphoprotein was identified specifically in the CD43+ T-cell line CEM, but not in their CD43-deficient counterparts derived by gene targeting. The 93-kD phosphoprotein was detected in the CD43-deficient CEM cells after transfection with CD43 cDNA, and it could be specifically phosphorylated in lysates from the CD43-deficient cells by incubation with a CD43 immunoprecipitate obtained from the CD43+ cells. Expression of CD43 in HeLa cell transfectants was associated with the appearance of novel phosphoproteins including one with a molecular weight of approximately 93 kD, confirming that tyrosine phosphorylation of cellular substrates results specifically from CD43 expression. We conclude that CD43 regulates tyrosine phosphorylation of a 93-kD T-cell substrate.

Antigens, CD↗
PubMed1995

Negative regulation of T-cell adhesion and activation by CD43.

CD43 is a cell-surface sialoglycoprotein expressed by a variety of haematopoietically derived cells, including T lymphocytes. Earlier observations of defective CD43 expression by T lymphocytes from boys with the X-chromosome-linked Wiskott-Aldrich syndrome suggested the importance of CD43 in lymphocyte function. Subsequent studies have suggested that CD43 facilitates leukocyte adhesion and has a co-stimulatory role during T-cell activation. To define the physiologically relevant function(s) of CD43, we have generated CD43-knockout mice. We report here that CD43-deficient T cells from such mice show a marked increase in their in vitro proliferative response to concanavalin A, anti-CD3, the superantigen SEB and allostimulation. Additionally, CD43-deficient T cells show a substantial enhancement in homotypic adhesion and in their ability to bind different ligands, including fibronectin and the intercellular adhesion molecule ICAM-1. Vaccinia-virus-infected CD43-knockout mice mounted an augmented anti-vaccinia cytotoxic T-cell response compared with their wild-type littermates, yet developed an increased virus load. We conclude that CD43 negatively regulates T-cell activation and adhesion and is important for viral clearance.

Animals↗
PubMed1995

CD43 diminishes susceptibility to T lymphocyte-mediated cytolysis.

CD43 is a major membrane sialoglycoprotein expressed by cells of hematopoietic origin. One property of CD43 is its ability to interfere with heterotypic and homotypic cellular adhesion. To determine whether CD43 expression can affect cell functions requiring intercellular adhesion, we compared a CD43-positive human T cell line (CEM) and its CD43-negative counterpart derived by gene targeting for susceptibility to cell-mediated lysis. CD43-negative CEM cells were more susceptible than CD43-positive cells to lysis by allospecific T cell lines derived from several donors. Induction of CD43 expression on transfected HeLa cells also imparted resistance to lectin-mediated lysis by a CD8+ T cell clone. The effect of CD43 expression on reducing susceptibility to lysis was more pronounced in short-term cytotoxicity assays and tended to disappear as the time of contact between the effector cell and its target increased. The enhanced susceptibility of CD43-negative cells to lysis was not associated with increased expression of adhesion molecules known to mediate antigen-independent cellular adhesion. Sialic acid residues on CD43 contributed to the CD43 protective effect. These results suggest that either diminished CD43 expression or incomplete sialylation may render hematopoietic cells more susceptible to T lymphocyte-mediated cytolysis.

Antigens, CD↗
PubMed1993

Targeted disruption of CD43 gene enhances T lymphocyte adhesion.

CD43 is a major leukocyte surface glycoprotein thought to have important functions for T lymphocyte adhesion and activation. We investigated the function of CD43 by using gene targeting to eliminate CD43 expression in the human T lymphocyte line CEM and then testing their adhesive phenotype. Loss of CD43 expression by the CEM cells enhanced their homotypic adhesion and binding to two distinct ligands, fibronectin and HIV-1 gp120. The enhanced homotypic adhesion was blocked specifically by an anti-beta 1 integrin mAb, and the enhanced binding to fibronectin and gp120 was blocked specifically by anti-beta 1 integrin and anti-CD4 mAb, respectively. Partial reconstitution of CD43 expression in the CD43-negative cells resulted in a corresponding reversion to a less adhesive phenotype. These data suggest that CD43 interferes with T lymphocyte adhesion and that CD43 can regulate lymphocyte adhesion by providing a threshold that must be overcome for cell-cell and cell-ligand interactions to occur.

Antigens, CD↗
PubMed1991

Rapid diagnosis of tuberculous meningitis by polymerase chain reaction.

The polymerase chain reaction (PCR) in cerebrospinal fluid was compared with conventional bacteriology and an enzyme-linked immunosorbent assay (ELISA) for cerebrospinal fluid antibodies in the diagnosis of tuberculous meningitis (TBM). PCR was the most sensitive technique; it detected 15 (75%) of 20 cases of highly probable TBM (based on clinical features), 4 (57%) of 7 probable cases, and 3 (43%) of 7 possible cases. ELISA detected 11 (55%) of the highly probable cases and 2 each of the probable and possible cases. Culture was positive in only 4 of the highly probable cases. Among the controls (14 pyogenic meningitis, 3 aseptic meningitis, 34 other neurological disorders), 6 subjects tested early in the study (2 pyogenic meningitis, 4 other disorders) were PCR positive. Second DNA preparations from their stored cerebrospinal fluid samples were all PCR negative, suggesting that the false-positive results were due to cross-contamination. 18 PCR-positive TBM samples retested were all still PCR positive. The antibody ELISA was positive in 3 controls despite the use of a high cutoff value.

Bacteriological Techniques↗
PubMed1991

Evaluation of a polymerase chain reaction for the diagnosis of tuberculosis.

A polymerase chain reaction for the specific detection of Mycobacterium tuberculosis has been developed and evaluated for clinical applicability. Primers were designed to amplify a 240 base pair region in the MPB 64 protein coding gene (nts 460-700). From among 15 different DNA templates tested (including 10 species of mycobacteria) PCR amplified the DNA from M. tuberculosis complex only, demonstrating its exquisite specificity. Sensitivity studies using serial ten-fold dilutions of M. tuberculosis bacilli determined the limit of detectability to be 10 organisms. A total of 143 clinical specimens were analysed. This consisted of 26 known non-tuberculous specimens (control group) and 117 specimens received at the Tuberculosis Diagnostic Service of AIIMS (test group). None of the specimens in the control group was positive by PCR. Out of 117 specimens in the test group, 19 were culture positive for mycobacteria and 17 of these isolates were identified as M. tuberculosis. All the specimens from which M. tuberculosis was grown were also PCR positive. The remaining two isolates were identified as mycobacteria other than M. tuberculosis and these two specimens were PCR negative. An additional 14 culture negative specimens were PCR positive yielding an overall M. tuberculosis positivity rate of 26.5% (31/117) compared to 14.5% (17/117) by culture. The superior sensitivity of PCR over culture was more evident in non-pulmonary cases where PCR picked up 10 cases in addition to three culture positives out of 69 specimens. On the other hand, out of 48 pulmonary specimens only four cases in addition to 14 culture positives were picked up by PCR.

Blotting, Southern↗
PubMed1989

A cytotoxic substance produced by a wild culture of Lactobacillus casei D-34 against tumour cells.

A wild lactic culture isolated from dahi (fermented milk) sample and characterised as L. casei D-34 was found to be significantly cytotoxic (34-36%) against three tumour cell lines, HeLa, HEp-2 and HFS-9. The cytotoxic substance (CS) was found to be in the culture supernatants, protein in nature, with a molecular weight ranging from 17,000-20,000. The crude culture supernatant was partially purified by dialysis and ion exchange chromatography as anionic, cationic and neutral fractions. Among the fractions, except for the anionic fraction, others were found to be highly cytotoxic against all three tumour cell lines. The cationic, neutral and pooled (anionic:cationic:neutral in 1:1:1 ratio) fractions showed 50, 70, 70% cytotoxicity against Hep-2 cells, 70, 88, 94% against HFS-9 cells and 50, 89, 90% against HeLa cells respectively. Pooled fraction was found to exhibit higher percent of cytotoxicity compared to individual fractions indicating a synergistic effect. (3H)-thymidine incorporation studies revealed that CS and its fractions inhibited DNA synthesis in tumour cells. The CS was stable towards heat and pH changes.

Animals↗
PubMed1989

Cytotoxic activity of lactobacilli isolated from plant and dairy sources.

Forty four cultures of Lactobacilli isolated from their natural sources such as dahi, raw milk and fermenting rice-pulse doughs etc. along with four standard strains of Lactobacilli were assayed for their cytotoxic activity against three secondary tumour cell lines. Three cultures isolated from dahi samples and identified as Lactobacillus casei D-34, L. casei D-48a, L. plantarum D-70a along with one standard strain L. casei B 1922 exhibited significant cytotoxic activity in the range of 30 to 36%.

Cell Survival↗
PubMed1989

Study of an outbreak of epidemic conjunctivitis in Delhi in 1986.

An epidemic of acute conjunctivitis occurred in Delhi during July-September 1986. The clinical presentation in total of 350 patients were characteristic of acute haemorrhagic conjunctivitis (AHC). Bacterial cultures from conjunctival swabs were sterile in 85 out of 105 (80%) patients, virus cultures in Vero and HeLa cells were negative in 30 patients. However, conjunctival scrapes from 20/30 (66.7%) patients showed specific cytoplasmic fluorescence with enterovirus 70 (EV 70) antiserum, suggesting EV 70 to be the etiologic agent of the epidemic.

Adolescent↗
PubMed1988

Correlation of histologic types of carcinoma of the uterine cervix and human papillomavirus and herpes simplex virus type 2 DNA sequences in the uterine cervical biopsies.

Forty patients with invasive cancer of cervix from New Delhi were examined for the presence of human papillomavirus (HPV) and herpes simplex virus (HSV) type 2 DNA sequences in a Southern hybridization assay. Data were analysed according to the histologic type of cancer. HPV DNA sequences were detected in 82.5% biopsies and HSV-2 DNA sequences were found in 10% biopsies. HPV-16 DNA sequences were found either alone or together with HPV-18 and/or HSV-2 Bgl II N fragment in 55% biopsies from keratinizing squamous cell carcinoma, whereas HPV-18 sequences were found in 35% biopsies. Similarly, 50% biopsies from patients with non keratinizing squamous cell carcinoma contained HPV-16 DNA and 38.9% biopsies had HPV-18 DNA. HSV-2 Bgl II N DNA sequences were present in 10% biopsies which were also positive for HPV-16 and/or HPV-18 DNA sequences. Two biopsies from adenocarcinoma of uterine cervix contained HPV-18 and HPV-16 DNA sequences. Therefore, no significant correlation seems to exist between HPV-types and histologic types or grades of differentiation of tumor.

Adenocarcinoma↗