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Biomedical subjects

S M Friedman

Publications and source records attributed to S M Friedman.

At least 19 recordsLinked to original sources
PubMed1995

Th1 CD4+ lymphocytes delete activated macrophages through the Fas/APO-1 antigen pathway.

The Fas/APO-1 cytotoxic pathway plays an important role in the regulation of peripheral immunity. Recent evidence indicates that this regulatory function operates through deletion of activated T and B lymphocytes by CD4+ T cells expressing the Fas ligand. Because macrophages play a key role in peripheral immunity, we asked whether Fas was involved in T-cell-macrophage interactions. Two-color flow cytometry revealed that Fas receptor (FasR) was expressed on resting murine peritoneal macrophages. FasR expression was upregulated after activation of macrophages with cytokines or lipopolysaccharide, although only tumor necrosis factor-alpha rendered macrophages sensitive to anti-FasR antibody-mediated death. To determine the consequence of antigen presentation by macrophages to CD4+ T cells, macrophages were pulsed with antigen and then incubated with either Th1 or Th2 cell lines or clones. Th1, but not Th2, T cells induced lysis of 60-80% of normal macrophages, whereas macrophages obtained from mice with mutations in the FasR were totally resistant to Th1-mediated cytotoxicity. Macrophage cytotoxicity depended upon specific antigen recognition by T cells and was major histocompatibility complex restricted. These findings indicate that, in addition to deletion of activated lymphocytes, Fas plays an important role in deletion of activated macrophages after antigen presentation to Th1 CD4+ T cells. Failure to delete macrophages that constitutively present self-antigens may contribute to the expression of autoimmunity in mice deficient in FasR (lpr) or Fas ligand (gld).

Animals↗
PubMed1995

CD40 ligation induces Apo-1/Fas expression on human B lymphocytes and facilitates apoptosis through the Apo-1/Fas pathway.

The Apo-1/Fas antigen (CD95) mediates programmed cell death of lymphocytes when bound by Fas ligand or anti-Apo-1/Fas antibody. In contrast, the CD40 antigen provides a potent activation and survival signal to B lymphocytes when it is engaged by its T cell ligand (CD40L, gp39) or cross-linked by anti-CD40 antibody. In this study, we use human tonsillar B cells and the Ramos Burkitt's lymphoma B cell line, which serves as a model for human germinal center B lymphocytes, to study the effectors of Apo-1/Fas expression and apoptosis of human B cells. We found that Apo-1/Fas expression was upregulated on both malignant and normal human B lymphocytes after CD40 ligation induced by (a) cognate T helper-B cell interaction mediated by microbial superantigen (SAg); (b) contact-dependent interaction with CD40L+, but not CD40L- Jurkat mutant T cell clones; and (c) monoclonal anti-CD40, but not any of a panel of control antibodies. Enhanced B cell Fas/Apo-1 expression is functionally significant. Coculture of Ramos Burkitt's lymphoma line cells with irradiated SAg-reactive CD4+ T cells with SAg or CD40L+ Jurkat T cells results in B cell apoptosis, evidenced by reduced cell viability and DNA laddering. This process is augmented by the addition of anti-Apo-1/Fas monoclonal antibody, consistent with an acquired susceptibility to Apo-1/Fas-mediated apoptosis. These data support an immunoregulatory pathway in which seemingly contradictory signals involving the B cell proliferation/survival antigen CD40, as well as the Apo-1/Fas molecule, which mediates programmed cell death of lymphocytes, are linked in the process of human B cell activation.

Antibodies, Monoclonal↗
PubMed1995

DNA supercoiling in a thermotolerant mutant of Escherichia coli.

A spontaneously occurring, nalidixic acid-resistant (NalR), thermotolerant (T/r) mutant of Escherichia coli was isolated. Bacteriophage P1-mediated transduction showed that NalR mapped at or near gyr A, one of the two genes encoding DNA gyrase. Expression of gyrA+ from a plasmid rendered the mutant sensitive to nalidixic acid and to high temperature, the result expected for alleles mapping in gyrA. Plasmid linking number measurements, made with DNA from cells grown at 37 degrees C or shifted to 48 degrees C, revealed that supercoiling was about 12% less negative in the T/r mutant than in the parental strain. Each strain preferentially expressed two different proteins at 48 degrees C. The genetic and supercoiling data indicate that thermotolerance can arise from an alteration in DNA gyrase that lowers supercoiling. This eubacterial study, when coupled with those of archaebacteria, suggests that DNA relaxation is a general aspect of thermotolerance.

Chromosome Mapping↗
PubMed1995

Human HLA-A0201-restricted cytotoxic T lymphocyte recognition of influenza A is dominated by T cells bearing the V beta 17 gene segment.

The major histocompatibility complex class I-restricted cytotoxic T lymphocyte (CTL) response is important in the clearance of viral infections in humans. After influenza A infection, a peptide from the matrix protein, M58-66, is presented in the context of the MHC allele HLA-A0201 and the resulting CTL response is detectable in most HLA-A0201 subjects. An initial study suggested that M58-66-specific CTL clones show conserved T cell receptor (TCR) alpha and beta gene segments. We have addressed the significance of this observation by determining the expression of V beta 17 during the development of M58-66-specific CTL lines in 21 unrelated HLA-A0201 subjects, and analyzing TCR usage by M58-66-specific CTL clones. TCR V beta 17 was the dominant V beta segment used and CD8 V beta 17 expansion correlated with M58-66-specific lysis. Limiting dilution analysis from five subjects showed the M58-66 CTL precursor frequency to vary between 1/54,000 and less than 1/250,000, and that up to 85% of the matrix peptide (M58-66)-specific CTL used the V beta 17 gene segment. The M58-66 specific CTL response was dependent on previous viral exposure and specific V beta 17 expansion, as it was not found in cord blood, despite a readily expandable V beta 17+ CD8+ T cell subpopulation. Sequence analysis of 38 M58-66-specific V beta 17 transcripts from 13 subjects revealed extensive conservation in the CDR3 region including conservation of an arginine-serine motif. To test the dependence of this CTL response on the V beta 17 gene segment, peripheral blood lymphocytes were depleted of CD8+ TCR V beta 17+ cells, before the generation of M58-66-specific CTL. In most cases such depletion blocked or severely reduced the generation of the M58-66-specific response, and under limiting dilution conditions could abolish M58-66-specific CTL precursors. These studies reveal the dependence of this natural human immune response on a particular TCR gene segment.

Alleles↗
PubMed1995

Bilateral central retinal vein occlusions in a patient with acquired immunodeficiency syndrome. Clinicopathologic correlation.

Four patients with human immunodeficiency virus (HIV) infection and central retinal vein occlusion have been previously described in the literature. The pathologic findings in a fifth patient with this association are reported. The histopathologic findings were similar to ischemic central retinal vein occlusion in persons without HIV infections. There was no evidence of HIV in vascular endothelial cells using electron microscopy and in situ hybridization techniques. The failure to identify any structural or direct infectious cause for central retina vein occlusion in this setting suggests that other hemorheologic factors related to HIV infection are probably responsible for the predisposition to vascular thrombosis.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Diabetic iris neovascularization.

PURPOSE: To compare the validity of careful slit-lamp biomicroscopic examination of the pupillary margin to screening gonioscopic examination in the early detection and prevention of neovascular glaucoma in diabetic patients. METHODS: We examined two patients with histories of diabetes mellitus. RESULTS: Angle neovascularization developed before iris neovascularization in both patients. CONCLUSION: We believe screening gonioscopic examination is valuable in patients with diabetes.

Diabetes Complications↗
PubMed1995

Increased fall rates in nursing home residents after relocation to a new facility.

OBJECTIVE: To examine the change in fall rates after relocation of nursing home residents from one facility to another and to identify resident risk factors for changes in falls following relocation. DESIGN: Retrospective review of incident reports to identify falls, followed by chart review of a longitudinal cohort. SETTING: An academic nursing home whose residents and programs moved from a 125-year-old, 233-bed facility to a newly constructed 255-bed facility. PATIENTS: A total of 210 nursing home residents were moved from one facility to the other. Of these, 133 individuals who lived in the old facility for 9 months before the move and in the new facility for 6 months after the move formed the longitudinal cohort. RESULTS: In the 3 months after the move, the fall rate increased from 0.34 to 0.70 falls per resident per quarter in the entire nursing home population (P < .001) and subsequently returned to baseline. In the longitudinal subgroup the fall rate went from 0.26 to 0.60 (P < .005). Fall-related injuries in the longitudinal subgroup went from 0.058 injuries per resident per quarter at baseline to 0.15 (P < .001). However, the injury rate per fall did not change. There were no characteristics associated with being a faller in the quarter before the move. Dementia and not being bedbound were associated with being a faller after the move. Individuals who were ambulatory or wheelchair mobile had a significant risk of increasing the number of falls after the move, and individuals with dementia had a strong but insignificant trend in this direction. CONCLUSIONS: The incidence of falling doubled after relocation of nursing home residents to a new facility. An increase in falls was seen in individuals who were not bedbound. Although nursing home relocation may be a relatively uncommon occurrence, it is reasonable to infer that older individuals who change their living environments are at increased risk for falls and fall-related injuries.

Accidental Falls↗
PubMed1994

Functional three-domain single-chain T-cell receptors.

T-cell receptors (TCRs) are membrane anchored heterodimers structurally related to antibody molecules. Single-chain antibodies can be engineered by linking the two variable domains, which fold properly by themselves. However, proper assembly of the variable domains of a human TCR (V alpha and V beta) that recognize the HLA-DR2b/myelin basic protein-(85-99) peptide complex was critically dependent on the addition of a third domain, the constant region of the TCR beta chain (C beta), to the single-chain construct. Single-chain molecules with the three-domain design, but not those with the two-domain design, expressed in a eukaryotic cell as chimeric molecules linked either to glycosyl phosphatidylinositol or to the transmembrane/cytoplasmic domains of the CD3 zeta chain were recognized by a conformation-sensitive monoclonal antibody. The chimeric three-domain single-chain TCR linked to CD3 zeta chain signaled in response to both the specific HLA-DR/peptide and the HLA-DR/superantigen staphylococcal enterotoxin B complexes. Thus, by using this three-domain design, functional single-chain TCR molecules were expressed with high efficiency. The lipid-linked single-chain TCR was solubilized by enzymatic cleavage and purified by affinity chromatography. The apparent requirement of the constant domain for cooperative folding of the two TCR variable domains may reflect significant structural differences between TCR and antibody molecules.

Amino Acid Sequence↗
PubMed1994

Experimental vitreous replacement with perfluorotri-n-propylamine.

OBJECTIVE: To evaluate perfluorotri-n-propylamine, a perfluorocarbon oil, as a temporary vitreous replacement in rabbits. METHODS: After undergoing gas compression vitrectomy, rabbits were injected with perfluorotri-n-propylamine for 24 hours or 2 weeks. The rabbits were evaluated clinically and with electroretinography. The globes were then enucleated and processed for histological evaluation. RESULTS: Clinical results showed droplet dispersion in the 2-week but not in the 24-hour group. Histological evaluation showed no changes in the retinal pigment epithelium or photoreceptor outer segments. Foam cells were seen in the 2-week but not in the 24-hour group. There was a marked dampening of the electroretinographic response that normalized after the removal of the oil. CONCLUSIONS: Perfluorotri-n-propylamine demonstrated no retinal toxic side effects in rabbits and is a promising liquid perfluorocarbon oil.

Animals↗
PubMed1994

Increased frequency of V beta 17-positive T cells in patients with rheumatoid arthritis.

OBJECTIVE: To identify the T lymphocytes that mediate disease in rheumatoid arthritis (RA). METHODS: A panel of monoclonal antibodies reactive with T cell receptor (TCR) V beta gene products was used to analyze the RA T cell repertoire. RESULTS: Of 5 TCR V beta gene products studied, only V beta 17-positive T cells were increased in peripheral blood and synovial fluid (SF) from RA patients, compared with controls (P < 0.01 and P = 0.0006, respectively). Thirty-one percent of the 49 RA SF samples and none of the 19 non-RA SF samples contained > 10% V beta 17-positive T cells. Activated (Tac-positive) T cells were enriched among V beta 17-positive synovial T cells. CONCLUSION: The selective increase of V beta 17-positive T cells suggests a role for those T cells in the pathogenesis of RA.

Adult↗
PubMed1994

Human T-cell responses to Mycoplasma arthritidis-derived superantigen.

When injected into mice, Mycoplasma arthritidis causes a chronic arthritis that resembles rheumatoid arthritis, histologically. The organism produces a superantigen termed Mycoplasma arthritidis mitogen or MAM, that in humans preferentially expands T cells whose antigen receptors express V beta 17. T cells with this phenotype appear to be increased in rheumatoid synovial effusions. We describe a novel approach to isolating and characterizing human MAM-reactive T-cell lines and determining their T-cell receptor (TCR) V beta usage. Lines were prepared from T cells that clustered with dendritic cells during a 2-day exposure to MAM. Cluster and noncluster fractions of T cells were then expanded by using feeder cells and a polyclonal mitogen. Most of the MAM reactivity was found in dendritic T-cell clusters, as were most of the T cells expressing TCR V beta 17. After expansion, 76% of the cluster-derived T-cell lines were MAM reactive, while no reactivity was seen in cell lines derived from the noncluster fraction. Of the MAM-reactive lines, 49% expressed V beta 17 on some or all of the cells. Cell lines from both cluster and noncluster fractions were analyzed for TCR V beta mRNA expression by PCR amplification. Other V beta genes (5.1, 7, 8, 12, and 20) were found to be expressed by lines that were MAM reactive, although these were not a major component of the cluster-derived T cells. Some non-cluster-derived lines expressed V beta s 17, 12, and 7, but these proved to be nonreactive to MAM. Therefore, dendritic cells can be used to immunoselect and characterize T cells that express superantigen-reactive TCRs.

Antigen-Presenting Cells↗
PubMed1994

The apoptosis-1/Fas protein in human systemic lupus erythematosus.

Three independent mutations involving the apoptosis-1 (APO-1)/Fas receptor or its putative ligand have led to lupuslike diseases associated with lymphadenopathy in different strains of mice. To determine whether humans with SLE also have a defect in this apotosis pathway, we analyzed the expression of APO-1 on freshly isolated blood mononuclear cells and on lymphocytes activated in vitro using flow cytometry and the monoclonal antibody anti-APO-1. Significantly higher level of APO-1 expression were detected on freshly isolated peripheral B cells and both CD4+ and CD8+ T lymphocyte populations obtained from lupus patients when compared with normal controls (P < 0.001). Almost 90% of the cells that stained positive for APO-1 also expressed the CD29 antigen, suggesting that APO-1 was upregulated after lymphocyte activation in vivo. No defect in APO-1 regulation was detected after activation of SLE T (with anti-CD3) or B (with Staphylococcus aureus Cowan 1) lymphocytes in the presence of IL-2 in vitro. Similarly, the anti-APO-1 antibody induced apoptosis in 74 +/- 5% of activated SLE T cells in vitro compared with 79 +/- 6% of the normal controls (P > 0.05). These results reveal that, while APO-1/Fas may play an important role in the regulation of lymphocyte survival in SLE, no consistent defect in the expression or function of the receptor could be detected in these studies.

Antigens, Surface↗
PubMed1994

CDR3 sequence motifs shared by oligoclonal rheumatoid arthritis synovial T cells. Evidence for an antigen-driven response.

T lymphocytes reactive with as yet undefined joint-localized foreign or autoantigens may be important in the pathogenesis of RA. Molecular studies demonstrating skewed T cell antigen receptor (TCR) variable gene usage and selective expansion of particular T cell clones within the synovial compartment support this view. Based on our recent study documenting selective expansion of V beta 17+ T cells in RA, we have pursued the identification of T cells relevant to the disease process, in an informative patient, by combining molecular analysis of freshly explanted RA synovial tissue V beta 17 TCR transcripts with in vitro expansion of V beta 17+ synovial tissue T cell clones. Peripheral blood V beta 17 cDNA transcripts proved heterogeneous. In contrast, two closely related sequences, not found in the peripheral blood, dominated synovial tissue V beta 17 transcripts, suggesting selective localization and oligoclonal expansion at the site of pathology. CD4+, V beta 17+ synovial tissue-derived T cell clones, isolated and grown in vitro, were found to express TCR beta chain transcripts homologous to the dominant V beta 17 synovial tissue sequences. One clone shares with a dominant synovial tissue sequence a conserved cluster of 4/5 amino acids (IGQ-N) in the highly diverse antigen binding CDR3 region, suggesting that the T cells from which these transcripts derive may recognize the same antigen. These findings have permitted a complete characterization of the alpha/beta TCR expressed by putatively pathogenic T cell clones in RA. Functional analysis suggests that the conserved CDR3 sequence may confer specificity for, or restriction by, the MHC class II antigen, DR4.

Aged↗
PubMed1993

Interaction of Mycoplasma arthritidis superantigen with human T cells.

To define the interaction site of T cell antigen receptors (TCRs) with the superantigen of Mycoplasma arthritidis (MAM), we characterized the TCRs of human MAM-reactive T cell lines and T cell clones. Most MAM-reactive T cells express the V beta 17 gene segment; however, other V beta may also be used and not all V beta 17+ TCRs are MAM-reactive. Alignment of MAM-reactive and MAM-nonreactive V beta sequences suggests that MAM does not interact with a single site encoded by a V beta segment but that several sites may be involved or that other TCR elements contribute to formation of the MAM recognition site.

Amino Acid Sequence↗