PubMed Health⌕ Search

Biomedical subjects

A Mirza

Publications and source records attributed to A Mirza.

At least 37 records · Page 2Linked to original sources
PubMed1995

The receptor DEC-205 expressed by dendritic cells and thymic epithelial cells is involved in antigen processing.

Dendritic cells and thymic epithelial cells perform important immunoregulatory functions by presenting antigens in the form of peptides bound to cell-surface major histocompatibility complex (MHC) molecules to T cells. Whereas B cells are known to present specific antigens efficiently through their surface immunoglobins, a comparable mechanism for the capture and efficient presentation of diverse antigens by dendritic cells and thymic epithelial cells has not previously been described. We show here that their antigen-presentation function is associated with the high-level expression of DEC-205, an integral membrane protein homologous to the macrophage mannose receptor and related receptors which are able to bind carbohydrates and mediate endocytosis. DEC-205 is rapidly taken up by means of coated pits and vesicles, and is delivered to a multivesicular endosomal compartment that resembles the MHC class II-containing vesicles implicated in antigen presentation. Rabbit antibodies that bind DEC-205 are presented to reactive T-cell hybridomas 100-fold more efficiently than rabbit antibodies that do not bind DEC-205. Thus DEC-205 is a novel endocytic receptor that can be used by dendritic cells and thymic epithelial cells to direct captured antigens from the extracellular space to a specialized antigen-processing compartment.

Amino Acid Sequence↗
PubMed1995

Tissue distribution of the DEC-205 protein that is detected by the monoclonal antibody NLDC-145. I. Expression on dendritic cells and other subsets of mouse leukocytes.

Prior studies by a variety of groups demonstrated that the mAb NLDC-145 reacted primarily with dendritic cells (DCs) and the epithelial cells of the thymic cortex. We recently reported that this mAb recognizes DEC-205, a 205-kDa integral membrane glycoprotein with a unique amino-terminal sequence, and raised a rabbit polyclonal antibody to purified DEC-205 with higher affinity for the blotted antigen than the original mAb. Here we utilize both the polyclonal and NLDC-145 to reassess the expression and function of DEC-205 on leukocytes. By cytofluorography, DCs derived from the epidermis (Langerhans cells) and from proliferating bone marrow progenitors (BMDCs) expressed high levels (2-3 logs) of DEC-205, while freshly isolated spleen DCs comprised two subsets, most (80%) staining at low levels (< or = 1 log), the remainder moderately (1.5 logs). DEC-205 epitopes were sensitive to trypsin, but were regenerated in culture. Resident and inflammatory peritoneal macrophages did not express the antigen, except for small amounts on thioglycollate-elicited cells. B cells from spleen, lymph node, bone marrow, blood, and peritoneal fluid expressed levels of DEC-205 that were 10- to 50-fold lower than those on BMDCs. Marrow pro- and pre-B cells did not express DEC-205. Polyclonal anti-DEC-205 failed to inhibit either stimulation of a primary mixed leukocyte reaction by DCs in vitro, or a local graft vs host response in vivo, where parental T cells were injected into F1 mice. DEC-205 is therefore more broadly expressed on leukocytes than previously appreciated, but its function remains unclear.

Animals↗
PubMed1995

Tissue distribution of the DEC-205 protein that is detected by the monoclonal antibody NLDC-145. II. Expression in situ in lymphoid and nonlymphoid tissues.

The rat monoclonal antibody NLDC-145, which has been utilized as a marker for mouse dendritic cells in numerous studies, binds an antigen that is more broadly distributed. This antigen is a unique 205-kDa integral membrane glycoprotein called DEC-205, which we have recently purified in quantities sufficient for basic biochemical studies, N-terminal sequencing, and immunization of rabbits. In cytofluorographic experiments, both the new polyclonal antibody and the original monoclonal detected DEC-205 on many classes of nondendritic murine leukocytes, particularly B cells. The quantities of DEC-205 on the surfaces of these cells were 10 to 50 times lower than those on epidermal and bone marrow dendritic cells. Here we utilize these reagents to reassess the tissue distribution of DEC-205 by immunohistochemical staining of frozen sections from a variety of organs, and by multiple-organ immunoblotting. Abundant expression of DEC-205 was confirmed histologically on thymic and intestinal epithelia and on dendritic cells in the T cell areas of peripheral lymphoid organs. In addition, DEC-205 was visualized in several other locations: B lymphocytes within B cell follicles, the stroma of the bone marrow, the epithelia of pulmonary airways, and the capillaries of the brain. Immunoblotting confirmed the presence of substantial levels of DEC-205 protein in lysates prepared from lymphoid tissues and from lung, marrow, and intestine. Thus, while DEC-205 is expressed at high levels by dendritic cells, it is also expressed by a number of other cell types in situ.

Animals↗
PubMed1993

Sequestration from immune CD4+ T cells of mycobacteria growing in human macrophages.

CD4+ helper T cells mediate resistance to tuberculosis, presumably by enhancing the antimicrobial activity of macrophages within which the Mycobacterium tuberculosis organism grows. A first step in resistance should be the presentation of mycobacterial antigens by macrophages to CD4+ T cells. However, when the antigenic stimulus is limited to organisms growing in human monocytes, the organisms become sequestered from immune CD4+ T cells. This block in presentation is selective for growing mycobacteria and not for other stimuli. Sequestration would allow replicating organisms to persist in infected individuals and may contribute to virulence.

Antigen-Presenting Cells↗
PubMed1993

Presentation of mycobacterial antigens by human dendritic cells: lack of transfer from infected macrophages.

When exposed to a challenge of 10 Mycobacterium bovis BCG cells per antigen-presenting cell, most human monocytes engulf several organisms. In contrast, blood dendritic cells which are potent antigen-presenting cells for several antigens are not detectably phagocytic for mycobacteria. We investigated the possibility that infected macrophages might regurgitate antigens for presentation by populations of human blood dendritic cells. Macrophages were infected with M. bovis BCG, mixed with uninfected dendritic cells, and added to immune T cells, either bulk T cells or cloned populations from BCG vaccinees or patients recovering from tuberculosis. The macrophages were from donors who were mismatched to the T cells so that transfer of antigen to major histocompatibility complex-matched dendritic cells could be evaluated. As we describe, there was no evidence for the transfer of mycobacterial antigens from macrophages to dendritic cells in a form that was stimulatory for the T cells.

Amino Acid Sequence↗
PubMed1992

Stimulation of adenovirus early gene expression by phorbol ester: its possible mechanism.

Treatment of Hela cells infected with adenovirus 5 wild type (Ad5WT) with the tumor-promoting phorbol ester TPA (12-O-tetradecanoyl phorbol-13-acetate), accelerated as well as stimulated expression of viral early genes EII and EIII but not that of EIA. TPA treatment of HeLa cells infected with dl312, an Ad5 EIA deletion mutant, activated expression of EIII but not EII. Stimulation of EII and EIII expression was blocked by H7 (1-5-isoquinolinyl sulfonyl-2-methyl piperazine), a specific inhibitor of protein kinase c (PKc). Nuclear run off assays demonstrated that TPA exerted a stimulatory effect at the level of transcription. PKc inhibitor alone reduced transcription of early genes in the absence of TPA activation. Phosphorylation of EIA 35 kDa but not 40- to 45-kDa proteins was dramatically increased by TPA. Three cellular proteins of 200, 24, and 20 kDa which coprecipitated with EIA proteins underwent enhanced and preferential phosphorylation by activated PKc. Inhibitor of PKc blocked phosphorylation of cellular proteins and reduced phosphorylation of EIA 35 kDa but not EIA 40- to 45-kDa proteins. These results tend to indicate that TPA stimulates adenovirus early gene expression through activation of protein kinase c and further suggest but do not prove that this may be due to specific phosphorylation of EIA 35 kDa and cellular proteins of 200, 24, and 20 kDa.

Adenoviridae↗
PubMed1992

Experimental studies on the acoustic properties of mastoid cavities.

This study investigated the effects of open-mastoid surgery upon ear canal resonance. In particular an attempt was made to alter resonant properties by obliterating each cavity with silastic foam. The results from this study showed that open-mastoid surgery significantly decreased resonant frequency without producing an effect upon either the peak amplitude or the quality of the resonant peak as defined by the Q-factor. Restoring the natural resonance properties of an operated ear, if indicated, is likely to be a difficult objective to achieve in surgical terms.

Acoustics↗
PubMed1992

DNA repair, cancer and gene therapy.

Fidelity of DNA synthesis is pivotal to our understanding of fundamental biological processes. An organism must replicate and repair its DNA with high accuracy and precision in order to maintain its genetic activity. DNA repair pathways enable cells to offer enhanced resistance to deleterious effects of chemicals and radiations (Lindahl, 1982). A number of pathways have been described e.g. the error-prone SOS repair (that lacks fidelity of repair process),the error-proof adaptive repair of alkylated DNA and inducible response to oxygen radical damage in DNA. These different circuits are under positive regulatory controls. However, the biochemical strategies employed to generate specific protein activators differ among the pathways. Although, the universally occurring repair activities seem to serve efficiently to counteract malignancy, error-prone polymerase and plasminogen activator have been instrumental in tumorigenesis, the process that proceeds by cascading of genetic errors (Sancar and Sancar, 1988).

Journal Article↗
PubMed1990

Nitrosoguanidine-induced adaptive repair in Pseudomonas aeruginosa.

Error-proof adaptive repair has been demonstrated in Pseudomonas aeruginosa. Cells of actively replicating wild-type Ps. aeruginosa (ATCC27853) and its auxotrophic derivative PAO 286 were subjected to stepwise adaptation (up to 1 microgram ml-1) by nitrosoguanidine (MNNG). Such cells resisted lethal and mutagenic effects of MNNG-challenge (lethal) doses more efficiently than those of nonadapted cultures. Similarly, reactivation of alkylated Pseudomonas phages was enhanced in adapted cells only. Induction of adaptive repair enzymes was sensitive to chloramphenicol (protein synthesis-inhibiting antibiotic) during adaptation treatment only. Protein extract from adapted cells showed increased levels in sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE).

Adaptation, Physiological↗
PubMed1988

Adenovirus transcriptional complexes contain EIa encoded tumour antigens physically bound to cellular proteins.

Adenovirus type 12 transcriptional complexes were isolated from cells during the early phase of infection. Sedimentation analysis identified a fast sedimenting complex type I and a slow sedimenting complex type II. Both complexes made virus specific RNA complementary to all the early genes and both contained viral DNA, which in type II but not in type I had nucleosome like configuration. Analysis of the proteins of the complexes with antiserum against Ad 12 EIa-beta-galactosidase fusion protein expressed in E. coli demonstrated the following: (a) type I complex contained EIa 45 K protein, which co-precipitated with cellular proteins of mol. wt. 42, 58, and 60 K, (b) type II complex contained EIa 47 K protein, which co-precipitated with major cellular proteins of 35, 40-46 K and minor proteins of 58, 60, 68, 76, 86, and 120-150 K. Association of EIa specific and cellular proteins to transcriptional complexes was sensitive to both 1 M NaCl and DNAse I indicating the DNA binding nature of these proteins. Treatment of transcriptional complexes with 1 M NaCl or DNase I released EIa proteins, which still remained strongly bound to cellular proteins. These findings suggested that EIa proteins bind to viral DNA and that this binding is probably mediated by cellular proteins.

Adenovirus Early Proteins↗
PubMed1986

Effect of linkage variation on pharmacokinetics of ricin A chain-antibody conjugates in normal rats.

We have investigated the pharmacokinetics of three ricin A chain-antibody conjugates having different bridging structures. Conjugate 1 has a disulphide linkage and was prepared with the N-succinimidyl-3-(2-pyridyldithio)propionate cross-linking reagent. Conjugate 2 has a protected disulphide linkage with a methyl group substituted on the carbon atom of the bridging structure adjacent to the disulphide linkage. Its preparation necessitated the synthesis of a new cross-linking reagent N-succinimidyl 3-(2-pyridyldithio)-butyrate. Conjugate 3 has a sulphide linkage and was prepared with the cross-linking reagent N-succinimidyl 4-(iodoacetylamino)benzoate which was synthesized by a novel route. Conjugate 1 is reducible, conjugate 2 less easily reducible and conjugate 3 nonreducible. On administration to animals all three conjugates displayed biphasic kinetics. The reducibility of the bond had no significant effect on the early disappearance of the conjugate from the circulation. However, at the later time points ease of reduction of the bond was associated with a more rapid disappearance of conjugate.

Animals↗
PubMed1980

Infectivity and uncoating of adenovirus cores.

A temperature-sensitive mutant of adenovirus type 2 grown at 39 degrees (tsl-39 degrees) produces noninfectious physical particles. DNA and core structures derived from such virion particles, however, were found to be infectious at the permissive temperature. Calcium chloride mediated transfection showed that core structures were 20-40 times more infectious than deprotenized DNA. Because in vivo the noninfectious ts1-39 degrees virions are blocked in uncoating at the core-like stage, we attempted to determine the reason for the infectivity of tsl-39 degrees cores prepared in vitro by investigating the metabolic fate of labeled cores in transfected cells. As opposed to infection with virus, the tsl-39 degrees cores were found to penetrate the nucleus efficiently and uncoat by shedding their core proteins. A possible explanation for the infectivity of the cores is discussed.

Adenoviruses, Human↗
PubMed1979

Hepatotoxicity of salicylazosulfapyridine: a case report and review of the literature.

A case report of a patient with biopsy-proven hepatitis which occurred while that patient was receiving Azulfidine which recurred after a rechallenge is presented. Toxic hepatitis, an apparent drug hypersensitivity reaction can result from Azulfidine therapy and must be considered in the differential diagnosis of hepatic abnormalities in patients with inflammatory bowel disease who are taking this drug. The literature concerning toxic reactions to the drug is reviewed.

Adult↗
PubMed1973

Association of nascent polypeptide with 30S ribosomal subunits.

1. Crude extracts of Escherichia coli were used to synthesize nascent peptides under the direction of endogenous mRNA and in the presence of radioactive amino acids. Analysis of such extracts by sucrose-gradient centrifugation in low Mg(2+) concentration has shown that after 2min of incubation approximately 14% of the total labelled protein recovered on the gradient, in association with whole ribosomes, sediments with 30S ribosomal subunits; this value rises to approximately 24% after 30min of incubation. The labelled protein associated with 30S ribosomal subunits is insoluble in hot trichloroacetic acid. 2. Similar results were also obtained in extracts that synthesized polypeptides under the direction of either of the synthetic polyribonucleotides poly(A) or poly(A,G,C,U). In contrast, however, analysis of crude extracts programmed in protein synthesis by poly(U) has indicated that under these conditions 30S ribosomal subunits have no associated polyphenylalanine; similarly there is little associated peptide after programming of extracts by poly(U,C).

Amino Acids↗