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At least 37 records · Page 2Linked to original sources
PubMed1979

Mechanism of cell-mediated cytotoxicity at the single cell level. II. Evidence for first-order kinetics of T cell-mediated cytolysis and for heterogeneity of lytic rate.

The kinetics and rate of T cell-mediated cytolysis was assessed by measuring the times required for lysis of isolated target cells by single cytotoxic lymphocytes. Single target cell lysis was determined microscopically by observing trypan blue uptake as a function of time of incubation of effector-target conjugates in agarose. Lysis of EL-4 target cells by alloimmune peritoneal exudate lymphocytes was initiated without a lag and was essentially complete at 2 hr. Both zero-order and first-order kinetics equations were analyzed for fit to the 0 to 2 hr lysis values. Statistically, the zero-order kinetic function could be rejected (p greater than 0.05), but the first-order kinetics function (p less than 0.01) could not. This strong evidence for first-order kinetics of T cell-mediated cytolysis implies that within each CTL-target cell population, cytolysis occurs exponentially as a random decay process and that one event in the entire process of cytolysis is rate limiting. The first-order equation was then applied to measurements of the rate of cytolysis in many different individual effector-target cell combinations. Significant differences in the lytic rate were apparent when either the effector or target cell were varied, with the rate constants spanning a 5-fold range. The heterogeneity of lytic rates is consistent with the hypothesis that lytic efficiency is a function of both the effector and target cells used.

Animals↗
PubMed1979

The basophil. Its morphology, biochemistry, motility, release reactions, recovery, and role in the inflammatory responses of IgE-mediated and cell-mediated origin.

The current state of our knowledge of basophils is reviewed. Much has recently been learned about these cells-their morphology, biochemical contents, interactions with homocytotropic antibodies, release of mediators in anaphylaxis, capacity for ingesting and releasing exogenous tracers, motility, participation in and progressive degranulation in cell-mediated hypersensitivity reactions, and their recovery from degranulation. It seems unlikely that basophils exist to destroy the organism by anaphylactic shock. Nonetheless, basophil function is probably closely related to the potent chemicals stored in their cytoplasmic granules. Perhaps small amounts of these chemicals are required for homeostasis and these cells function by releasing such substances as they are needed. This hypothesis requires that basophils be capable of releasing their contents slowly and piecemeal, which apparently occurs. This hypothesis also requires that physiological, rather than pharmacological, roles be found for histamine.

Animals↗
PubMed1977

III. Mediators of allergic reactions. Endogenous and exogenous stimulating or suppressor substances. Mediators of experimental hypersensitivity pneumonitis.

Using a physiologic model of hypersensitivity pneumonitis where depressions of arterial oxygen tension in unimmunized rabbits are monitored following aerosol challenge with Aspergillus terreus spores, attempts were made to assess the nature of the cellular and pharmacologic mediators of the impairment. Unlike normal animals no PaO2 depressions were obtained following aerosol challenge in either rabbits deficient in C6 or in rabbits made thrombocytopenic with antiplatelet serum. Such aerosols were also shown to produce platelet count depressions of up to 45% in normal rabbits. Finally, in vitro evidence of histamine release was obtained following incubation of Aspergillus extract, platelets and autologous serum from unimmunized rabbits. It was concluded that Aspergillus-induced pulmonary disease may be initiated by platelet release of mediators such as histamine stimulated by nonspecific complement activation.

Aerosols↗
PubMed1975

Cell-mediated immunity: differential maturation of mixed leukocyte reaction and cell-mediated lympholysis.

While spleen cells from neonatal B10 (H-2b) are reactive (proliferate) in one-way mixed leukocyte culture, cell-mediated lympholysis reactivity does not arise until 7 days of age. When B10 cells are sensitized to B10.D2 (H-2d), cross-killing of third-party B10.BR (H-2k) target is always lower than the specific killing of B10.D2 targets and is not demonstrable until 27 days after birth.

Aging↗
PubMed1977

Mechanisms of resistant of herpesviruses: comparison of the effectiveness of different cell types in mediating antibody-dependent cell-mediated cytotoxicity.

Enriched populations of polymorphonuclear leukocytes (PMN) and macrophages obtained from the mammary gland and of granulocytes (PBG) and lymphocytes (PBL) prepared from peripheral blood of the same animal were compared for their ability to mediate antibody-dependent cell cytotoxocity against antibody-sensitized infectious bovine rhinotracheitis virus-infected target cells (IBR-GBK) and antibody-sensitized chicken erythrocyte targest (CRBC). The order of effectiveness was PMN leads to macrophages leads to PBG leads to PBL. The reason why PBG (86% PMN) were less than 50% as active as mammary PMN (99% PMN) was explored and discussed. The findings that PMN were more effective on a cell-to-cell basis, required less antiserum to sensitize for cytotoxicity, and destroyed IBR-GBK cells faster and more completely than other cell types could mean that PMN may be the cell type most importnat in causing early recovery from herpesvirus infections.

Animals↗
PubMed1978

Impaired cell-mediated immunity in Hodgkin's disease mediated by suppressor lymphocytes and monocytes.

In Hodgkin's disease a possible mechanism for impaired cellular immunity is cell-mediated suppression, defined as the inhibitory interaction between suppressor cells and effector lymphocytes. To test for the presence of suppressor cells in peripheral blood, we have modified the standard, one-way mixed lymphocyte culture by adding mitomycin C-treated mononuclear cells from the responder. Suppression, expressed as a percent of the base-line mixed lymphocyte culture in which these extra cells are not present, results in a reduction of thymidine incorporated in the modified culture (i.e., 100% suppression = no net thymidine incorporation; 0% suppression = identical thymidine incorporation in both the modified and baseline culture). Suppression was found to be significantly increased in patients with both active Hodgkin's disease (78+/-4.6%) and remission Hodgkin's disease (58+/-9.3%) compared to normal individuals (21+/-6.9%) (mean+/-SE). The degree and frequency of suppression were not influenced by disease stage or prior therapy. Cell purification techniques revealed (in 10 patients studied) the suppressor cell to be a monocyte in 6, and a thymus-derived lymphocyte in 4. Possible genetic restriction of the suppressor cell interaction was indicated by a failure of suppressor cells to alter the response of lymphocytes from unrelated individuals, but suppression was obtained with lymphocytes from a histocompatible sibling. Although mononuclear cells from normal individuals suppress less frequently than cells from patients with Hodgkin's disease, normals may demonstrate suppression comparable to that observed in Hodgkin's patients. This finding suggests that suppression is a normal immunoregulatory mechanism which is altered in Hodgkin's disease.

Adolescent↗
PubMed1976

Antigen-specific and nonspecific mediators of T cell/B cell cooperation. III. Characterization of the nonspecific mediator(s) from different sources.

T cell-containing lymphoid populations produce a nonantigen-specific mediator(s) (NSM) which can replace T cell helper function in vitro in the response of B cells to sheep red blood cells (SRBC), but not to the hapten-protein conjugate, trinitrophenyl-keyhole limpet hemocyanin, (TNP-KLH). NSM produced under three conditions: 1) stimulation of KLH-primed cells with KLH; 2) allogeneic stimulation of normal spleen cells; and 3) stimulation of normal spleen cells with Con A (but not PHA) are indistinguishable on the basis of their biologic activity and m.w., estimated as 30 to 40,000 daltons by G-200 chromatography. Production of NSM is dependent on the presence of T cells. The action of NSM on B cells responding to SRBC in the presence of 2-mercaptoethanol is unaffected by severe macrophage depletion. Extensive absorption of NSM with SRBC failed to remove its activity, confirming its nonantigen-specific nature.

Animals↗
PubMed1976

Cell-mediated immunity to friend virus-induced leukemia. IV. In vitro generation of primary and secondary cell-mediated cytotoxic responses.

Primary and secondary cell-mediated cytotoxic responses to FBL-3 cells, a syngeneic Friend virus-induced leukemia in C57BL/6 mice, could be generated by in vitro techniques as tested by the 125IUdR release assay. The specificity of the cytotoxic reactions appeared to be directed against the Friend type-specific antigen and the FMR (Friend, Moloney, Rauscher) antigen which were also the major antigens for transplantation immunity to FBL-3. In comparison to the primary cytotoxic response, the secondary cytotoxic response was accelerated (detected at an earlier time after sensitization), enhanced (gave much higher levels of cytotoxicity), was also longer lasting, and could be induced by a wide dose range of tumor cells. The secondary response could only be induced with lymphocytes obtained from regressors that were resistant to FBL-3 challenge; lymphocytes from mice with progressive tumor growth had no detectable secondary response. It was found that both induction phase and the effector phase of cytotoxic responses were T cell dependent. The characteristics of these reactions were thus very similar to those obtained with in vivo immunization or challenge, providing a good correlation with in vivo tumor immunity.

Animals↗
PubMed1978

Leukocyte-adherence inhibition: a specific assay of cell-mediated immunity dependent on lymphokine-mediated collaboration between T lymphocytes.

The leukocyte-adherence inhibition (LAI) assay was studied to determine its immunologic relevance and identify the cell populations on which it depends. Two systems were employed: peripheral blood leukocytes from humans immunized with KLH, and lymph node cells from rats immunized with DNP-BCG. In both cases, LAI responses appeared about 3 to 4 days after immunization, reached a peak about 3 to 4 weeks later, and diminished thereafter. Reimmunization resulted in a booster-like response. LAI analysis in both systems showed dose-response dependency. Responses could be elicited only with the immunizing antigen. Virtual depletion of phagocytic cells had no effect on the response. E-rosette-forming cells gave an excellent response to KLH and also produced an active supernatant (lymphokine). Cells not forming spontaneous E-rosettes were inactive and could not produce active supernatants. Only those nonimmune cells that formed E-rosettes could respond to active supernatants. Thus, the LAI response is a specific indicator of cell-mediated immunity. T lymphocytes probably are required both at the antigen-reactive stage and at the stage of responding to the T cell-dependent lymphokine.

Animals↗
PubMed1978

Cell-mediated cytotoxicity and serum-mediated blocking: evidence that their associated determinants on human tumor cells are different.

The preceding paper showed that patients with gliomas may have lymphocyte-mediated cytotoxic activity (LMC) directed against at least two determinants on the glioma cell surface. The present study showed that serum from patients with gliomas could block this LMC. The blocking activity, however, was specific for different determinants on the glioma cell than those to which the LMC was directed. Blocking activity was specific for tumor cells homotypic to those of the serum donor. It was effective, however, in blocking the cytotoxic activity against these cells of lymphocytes from patients with tumors either homotypic or heterotypic to that of the serum donor. Likewise, although patients with glioblastomas or melanomas had LMC against fetal glial cells, sera from such patients were unable to block the LMC against these fetal glial targets. The specificity of the blocking activity was confirmed by absorption of the sera with various normal and neoplastic cells. These studies have thus shown an immunologic functional dichotomy among different determinants on the glioma cell surface.

Absorption↗
PubMed1976

Studies of the mechanism of lymphocyte-mediated cytolysis. VII. Two stages in the T cell-mediated lytic cycle with distinct cation requirements.

The lysis of allogeneic cells by cytolytically active T lymphocytes has been shown to involve two stages, Each with distinct cation requirements. Cytolysis required the presence of Ca++ ions, but addition of Mg++ to Ca++ containing medium synergistically enhanced target cell destruction. This synergistic effect resulted form kinetically separable events mediated by these cations. Thus, optimal adhesions between killer and target cells necessitated the presence of Mg++; interactions also occurred, but less efficiently, in the presence of Ca++. Lymphocyte-target cell interactions resulting from the present of Mg++ did not lead to the lysis of the target cell, until Ca++ were added. A "late" stage of the establishment of a target cell lesion is thus uniquely served by Ca++.

Animals↗
PubMed2026

Phytoplasma-plant interactions: effector-mediated host reprogramming, hormonal crosstalk, metabolic alterations and plant-mediated vector manipulation.

Phytoplasmas are wall-less, phloem-restricted bacterial pathogens that infect over 1,000 plant species, causing substantial losses in agriculture, horticulture, and forestry worldwide. Despite their reduced genomes and limited metabolic autonomy, these obligate parasites colonize diverse hosts through secreted effector proteins that extensively reprogram plant development, metabolism, immune signalling, and vector interactions. Advances in genomics, transcriptomics, proteomics, metabolomics, and functional studies have substantially clarified the molecular basis of phytoplasma pathogenicity and symptom development. This review synthesizes current understanding of phytoplasma-plant interactions, covering phytoplasma biology, genome evolution, and the infection cycle across plant and insect vector hosts. We examine the molecular functions of key effectors, SAP11, SAP54/PHYL1, SAP05, TENGU, SWP1, and recently identified virulence factors, focusing on how they target host transcription factors, phytohormone networks, protein degradation pathways, and immune responses to promote colonization and disease progression. We further discuss how phytoplasma infection disrupts phytohormone signalling, primary and secondary metabolism, and developmental programs to produce characteristic disease symptoms, with particular attention to pathogen-induced changes in host volatiles and nutritional quality that alter vector behaviour and enhance transmission. Finally, we summarize insights from multi-omics studies and emerging management strategies, including CRISPR-based genome editing, RNAi, rapid molecular diagnostics, resistant cultivars, microbiome-based approaches, and sustainable vector control, and highlight key knowledge gaps and priorities for developing effective, environmentally sustainable phytoplasma disease management.

Phytoplasma↗
PubMed1976

Excitation-mediating and inhibition-mediating dopamine-receptors: a new concept towards a better understanding of electrophysiological, biochemical, pharmacological, functional and clinical data.

A great number of earlier reported experimental data dealing with the role of dopamine in dopamine-loaded structures within the mammalian brain have raised questions concerning the concept of dopamine as an inhibitory agent acting on one type of receptor. A critical review of the anatomical, histochemical, electrophysiological, pharmacological and functional studies reveals that the dopamine-loaded structures are marked by an internal differentiation at various levels. It is attempted to demonstrate that this is due to a heterogeneous distribution of two distinct types of dopamine-receptors, each characterized by their own properties: DAe and DAi-receptors. Furthermore, the experimental and clinical implications are discussed in view of the hypothesis that balance between both types of receptors is essential for normal psychomotor functioning.

Amphetamines↗