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S Sharrow

Publications and source records attributed to S Sharrow.

10 recordsLinked to original sources
PubMed2001

Maturation versus death of developing double-positive thymocytes reflects competing effects on Bcl-2 expression and can be regulated by the intensity of CD28 costimulation.

Immature double-positive (DP) thymocytes mature into CD4(+)CD8(-) cells in response to coengagement of TCR with any of a variety of cell surface "coinducer" receptors, including CD2. In contrast, DP thymocytes are signaled to undergo apoptosis by coengagement of TCR with CD28 costimulatory receptors, but the molecular basis for DP thymocyte apoptosis by TCR plus CD28 coengagement is not known. In the present study, we report that TCR plus CD28 coengagement does not invariably induce DP thymocyte apoptosis but, depending on the intensity of CD28 costimulation, can induce DP thymocyte maturation. We demonstrate that distinct but interacting signal transduction pathways mediate DP thymocyte maturation signals and DP thymocyte apoptotic signals. Specifically, DP maturation signals are transduced by the extracellular signal-related kinase (ERK)/mitogen-activated protein kinase (MAPK) pathway and up-regulate expression of the antiapoptotic protein Bcl-2. In contrast, the apoptotic response stimulated by CD28 costimulatory signals is mediated by ERK/MAPK-independent pathways. Importantly, when TCR-activated thymocytes are simultaneously coengaged by both CD28 and CD2 receptors, CD28 signals can inhibit ERK/MAPK-dependent Bcl-2 protein up-regulation. Thus, there is cross-talk between the signal transduction pathways that transduce apoptotic and maturation responses, enabling CD28-initiated signal transduction pathways to both stimulate DP thymocyte apoptosis and also negatively regulate maturation responses initiated by TCR plus CD2 coengagement.

Animals↗
PubMed1997

Preassembly of interleukin 2 (IL-2) receptor subunits on resting Kit 225 K6 T cells and their modulation by IL-2, IL-7, and IL-15: a fluorescence resonance energy transfer study.

Assembly and mutual proximities of alpha, beta, and gamma(c) subunits of the interleukin 2 receptors (IL-2R) in plasma membranes of Kit 225 K6 T lymphoma cells were investigated by fluorescence resonance energy transfer (FRET) using fluorescein isothiocyanate- and Cy3-conjugated monoclonal antibodies (mAbs) that were directed against the IL-2R alpha, IL-2R beta, and gamma(c) subunits of IL-2R. The cell-surface distribution of subunits was analyzed at the nanometer scale (2-10 nm) by FRET on a cell-by-cell basis. The cells were probed in resting phase and after coculture with saturating concentrations of IL-2, IL-7, and IL-15. FRET data from donor- and acceptor-labeled IL-2R beta-alpha, gamma-alpha, and gamma-beta pairs demonstrated close proximity of all subunits to each other in the plasma membrane of resting T cells. These mutual proximities do not appear to represent mAb-induced microaggregation, because FRET measurements with Fab fragments of the mAbs gave similar results. The relative proximities were meaningfully modulated by binding of IL-2, IL-7, and IL-15. Based on FRET analysis the topology of the three subunits at the surface of resting cells can be best described by a "triangular model" in the absence of added interleukins. IL-2 strengthens the bridges between the subunits, making the triangle more compact. IL-7 and IL-15 act in the opposite direction by opening the triangle possibly because they associate their private specific alpha receptors with the beta and/or gamma(c) subunits of the IL-2R complex. These data suggest that IL-2R subunits are already colocalized in resting T cells and do not require cytokine-induced redistribution. This colocalization is significantly modulated by binding of relevant interleukins in a cytokine-specific manner.

Adult↗
PubMed1993

Structurally distinct T cell receptor complexes on developmentally distinct T cell populations in severe combined immunodeficiency mice expressing a TCR beta transgene.

T cell differentiation and TCR expression were assessed in severe combined immunodeficiency (SCID) mice possessing an already rearranged TCRV beta 8 transgene. Unlike nontransgenic SCID mice, TCRV beta 8-transgenic SCID mice contained a broad spectrum of T cell populations, including both immature thymocytes and mature T cells. In TCRV beta 8-transgenic SCID mice, immature CD4-CD8- and CD4+CD8+ thymocytes expressed surface TCR complexes structurally distinct from those expressed by mature single-positive T cells. Immature CD4+CD8+ thymocytes expressed surface TCR beta chains without a clonotypic TCR partner chain and largely without associated CD3 components. In contrast, mature single-positive T cells expressed fully assembled surface TCR complexes containing disulfide-linked heterodimers consisting of transgenic TCR beta chains and endogenous TCR alpha chains. The surface TCR complexes on mature T cells were associated with CD3 components and were competent to transduce TCR-mediated proliferative signals. Thus, T cells at different stages of development in TCRV beta 8-transgenic SCID mice express structurally distinct surface TCR complexes, demonstrating that the developmental stage achieved by T cells in these mice is related to the structure of the surface TCR complexes they express. Indeed, the present results indicate that successful differentiation into single-positive T cells requires surface expression of fully assembled TCR complexes.

Animals↗
PubMed1989

Induction of macrophage tumoricidal activity, major histocompatibility complex class II antigen (Iak) expression, and interleukin-1 production by swainsonine.

Previous studies in our laboratory have shown that the reported antitumor activity of systemically administered swainsonine, an indolizidine alkaloid, is due at least in part to immune modulation involving effector cells (Humphries, M.J.; Matsumoto, K; White, S.L.; Olden, K. Cancer Res. 48:1410-1415; 1988 and White, S. L.; Schweitzer, K.; Humphries, M.J.; Olden, K. Biochem. Biophys. Res. Commun. 150:615-625; 1988). In this report, studies are presented to show that swainsonine was effective in activating peritoneal macrophages to cytotoxicity against tumor cells. Stimulation of tumoricidal activity of macrophages was associated with increased secretion of interleukin-1 (IL-1) and expression of the Iak major histocompatibility complex (MHC) antigen on the cell surface. The 3-fold stimulation of cytotoxicity observed in these in vivo studies was comparable to that obtained with Corynebacterium parvum, a commonly used in vivo activating agent. The in vitro incubation of thioglycollate-elicited peritoneal macrophages with swainsonine consistently resulted in levels of activation (6- to 8-fold) comparable to that obtained by treatment with known in vitro macrophage activating agents such as lipopolysaccharide (LPS) or recombinant gamma-interferon (rIFN-gamma). The stimulation observed by using swainsonine in combination with LPS was additive, suggesting different mechanisms of action. These studies have important implications not only for treatment of cancer, infectious diseases, and immune suppressive disorders, but also for elucidation of the mechanism of macrophage activation.

Alkaloids↗
PubMed1985

Interleukin 2 receptor (Tac antigen) expression in HTLV-I-associated adult T-cell leukemia.

Interleukin-2 (IL-2) is a lymphokine synthesized by some T-cells following activation. Resting T-cells do not express IL-2 receptors, but receptors are rapidly expressed on T-cells following interaction of antigens, mitogens, or monoclonal antibodies with the antigen-specific T-cell receptor complex. Using anti-Tac, a monoclonal antibody that recognizes the IL-2 receptor, the receptor has been purified and shown to be a Mr 33,000 peptide that is posttranslationally glycosylated to a Mr 55,000 mature form. Normal resting T-cells and most leukemic T-cell populations do not express IL-2 receptors; however, the leukemic cells of the 11 patients examined who had human T-cell lymphotropic virus-associated adult T-cell leukemia expressed the Tac antigen. In human T-cell lymphotropic virus-I infected cells, the Mr 42,000 long open reading frame protein encoded in part by the pX region of this virus may act as a transacting transcriptional activator that induces IL-2 receptor gene transcription, thus providing an explanation for the constant association of IL-2 receptor expression with adult T-cell lymphotropic virus-I infection of lymphoid cells. The constant expression of large numbers of IL-2 receptors which may be aberrant may play a role in the uncontrolled growth of adult T-cell leukemia cells. Two patients with Tac-positive adult T-cell leukemia have been treated with the anti-Tac. One of the patients had 6- and 3-mo remissions of his leukemia following two courses of therapy with this monoclonal antibody directed toward this growth factor receptor.

Adult↗
PubMed1984

Functional and phenotypic comparison of human T cell leukemia/lymphoma virus positive adult T cell leukemia with human T cell leukemia/lymphoma virus negative Sézary leukemia, and their distinction using anti-Tac. Monoclonal antibody identifying the human receptor for T cell growth factor.

Adult T cell leukemia (ATL) and Sézary leukemia are malignant proliferations of T lymphocytes that share similar cell morphology and clinical features. ATL is associated with HTLV (human T cell leukemia/lymphoma virus), a unique human type C retrovirus, whereas most patients with the Sézary syndrome do not have antibodies to this virus. Leukemic cells of both groups were of the T3, T4-positive, T8-negative phenotype. Despite the similar phenotype, HTLV-negative Sézary leukemic cells frequently functioned as helper cells, whereas some HTLV-positive ATL and HTLV-positive Sézary cells appeared to function as suppressors of immunoglobulin synthesis. One can distinguish the HTLV-positive from the HTLV-negative leukemias using a monoclonal antibody (anti-Tac) that appears to identify the human receptor for T cell growth factor (TCGF). Resting normal T cells and most HTLV-negative Sézary cells were Tac-negative, whereas all ATL cell populations were Tac-positive. The observation that ATL cells manifest TCGF receptors suggests the possibility that an abnormality of the TCGF-TCGF receptor system may partially explain the uncontrolled growth of these cells.

Adult↗
PubMed1983

Analysis of thymocyte subpopulations following treatment with sex hormones.

Sex steroids were found to affect both murine and avian immune systems. Female and male (NZB X NZW)F1 mice were castrated at 2 weeks of age and given Silastic implants containing either dihydrotestosterone or estradiol. Four weeks following treatment, the thymuses were studied for cell cycle kinetics and for the presence of various cell surface antigens using fluorescein-conjugated antisera and flow cytometric techniques. Estradiol therapy resulted in an increase in mature thymocytes, that is, thymocytes that had decreased peanut agglutinin receptors and decreased Thy 1 antigens on their surfaces. Additional studies with anti-Lyt 1 and 2 indicated that these mature thymocytes were of the "helper" rather than the "suppressor" phenotype. Estradiol therapy resulted in an increase in the percentages of proliferating cells in the spleen and a decrease in the percentages of proliferating cells in the thymus. In contrast, in the avian system, estradiol had little effect on proliferation in immunological organs. Dihydrotestosterone was a potent inhibitor of proliferation in the avian bursa. These results indicate that sex hormones have specific effects on different immune cell subpopulations. In the murine system the male is the heterogametic sex but in the avian system the female is the heterogametic sex. Based upon the present and previous studies, we suggest that the primary modulating hormone for immunological sex effects in the mammal is estrogen, whereas in the bird it is androgen.

Animals↗
PubMed1981

Activation of leukemic pro-suppressor cells to become suppressor-effector cells. Influence of cooperating normal T cells.

We studied the suppressor activity and surface-membrane antigens of immunoregulatory neoplastic T cells from a child with acute lymphoblastic leukemia and hypogammaglobulinemia. The neoplastic T cells were potent inhibitors of immunoglobulin production by pokeweed-mitogen-stimulated normal B cells when radiosensitive cooperative normal T cells were present. Preculturing the leukemic cells with normal T cells or soluble factors allowed them to mediate suppression without the need for cooperating T cells. While acquiring new functional capabilities, approximately 95 per cent of the leukemic cells displayed an antigen (OKT-3) that is found on mature normal T cells; 77 per cent displayed an antigen (Tac) that is found on normal activated immunoregulatory effector cells but not on thymocytes or circulating T cells that are precursors of these effector cells. The results suggest that a population of leukemic prosuppressor cells can be induced to undergo both functional and antigenic differentiation by the influence of normal T cells.

Agammaglobulinemia↗
PubMed1981

Preparative nonlytic separation of Lyt2+ and Lyt2- T lymphocytes, functional analyses of the separated cells and demonstration of synergy in graft-vs.-host reaction of Lyt2+ and Lyt2- cells.

A convenient, preparative scale, nonlytic separation of mouse T lymphocytes into Lyt2.2+ and Lyt2.2- populations is reported. Immunoglobulin-negative (Ig-) spleen cells, Ig- lymph node cells, and peanut lectin-unagglutinated (PNA-) thymocytes were incubated under sterile conditions at 0 degree C with monoclonal mouse antibody to the Lyt2.2 T cell differentiation antigen. The antibody-treated cells were washed and placed in polystyrene tissue culture dishes that had been precoated with antibody to mouse Ig. Nonadherent populations were depleted to Lyt2.2+ cells and were essentially devoid of cytotoxic T lymphocyte precursors (CTLp), but contained helper activity for in vivo T-dependent IgM, IgG and IgA antibody formation. Adherent cell populations were enriched for Lyt2.2+ cells and for CTLp. The graft-vs.-host activity of the separated, adherent (Lyt2.2+) and nonadherent (Lyt2.2-) cells in the Simonsen spleen assay in neonatal (C57BL/6 x BALB/c)F1 mice was less than of unfractionated cells, but the activity of remixed Lyt2.2+ plus Lyt2.2- cells was higher than the sum of the contributions of these cells tested separately, and equal to that of the unfractionated cells. PNA- thymocytes were also separated into Ly2.2+ and Lyt2.2- populations by fluorescence-activated cell sorting. Nonlytic separation allows the recovery of the Lyt1+2+ population, which is lost in cytotoxic elimination experiments. Under the conditions described for the plate separation, the purity of the separated cells and recovery of activity approaches that of cells separated by sorting. Therefore, the plate separation offers a convenient alternative to fluorescence-activated cell sorting when large numbers (i.e. up to 5 x 10(7) positively selected cells) are needed, as in studies of in vivo cell-mediated immune reactions.

Animals↗