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At least 19 recordsLinked to original sources
PubMed2025

S-GMAS: Genome-Wide Mediation Analysis With Brain Subcortical Shape Mediators.

Mediation analysis is widely utilized in neuroscience to investigate the role of brain image phenotypes in the neurological pathways from genetic exposures to clinical outcomes. However, it is still difficult to conduct mediation analyses with whole genome-wide exposures and brain subcortical shape mediators due to several challenges including (i) large-scale genetic exposures, that is, millions of single-nucleotide polymorphisms (SNPs); (ii) nonlinear Hilbert space for shape mediators; and (iii) statistical inference on the direct and indirect effects. To tackle these challenges, this paper proposes a genome-wide mediation analysis framework with brain subcortical shape mediators. First, to address the issue caused by the high dimensionality in genetic exposures, a fast genome-wide association analysis is conducted to discover potential genetic variants with significant genetic effects on the clinical outcome. Second, the square-root velocity function representations are extracted from the brain subcortical shapes, which fall in an unconstrained linear Hilbert subspace. Third, to identify the underlying causal pathways from the detected SNPs to the clinical outcome implicitly through the shape mediators, we utilize a shape mediation analysis framework consisting of a shape-on-scalar model and a scalar-on-shape model. Furthermore, the bootstrap resampling approach is adopted to investigate both global and spatial significant mediation effects. Finally, our framework is applied to the corpus callosum shape data from the Alzheimer's Disease Neuroimaging Initiative.

Humans↗
PubMed2024

Mannose receptor (MRC1) mediates uptake of dextran in macrophages via receptor-mediated endocytosis.

UNLABELLED: Macrophages maintain surveillance of their environment using receptor-mediated endocytosis and pinocytosis. Receptor-mediated endocytosis allows macrophages to recognize and internalize specific ligands whereas macropinocytosis non-selectively internalizes extracellular fluids and solutes. Here, CRISPR/Cas9 whole-genome screens were used to identify genes regulating constitutive and growth factor-stimulated dextran uptake in murine bone-marrow derived macrophages (BMDM). The endocytic mannose receptor c-type 1 ( Mrc1 , also known as CD206) was a top hit in the screen. Targeted gene disruptions of Mrc1 reduced dextran uptake but had little effect on uptake of Lucifer yellow, a fluid-phase marker. Other screen hits also differentially affected the uptake of dextran and Lucifer yellow, indicating the solutes are internalized by different mechanisms. We further deduced that BMDMs take up dextran via MRC1-mediated endocytosis by showing that competition with mannan, a ligand of MRC1, as well as treatment with Dyngo-4a, a dynamin inhibitor, reduced dextran uptake. Finally, we observed that IL4-treated BMDM internalize more dextran than untreated BMDM by upregulating MRC1 expression. These results demonstrate that dextran is not an effective marker for the bulk uptake of fluids and solutes by macropinocytosis since it is internalized by both macropinocytosis and receptor-mediated endocytosis in cells expressing MRC1. This report identifies numerous genes that regulate dextran internalization in primary murine macrophages and predicts cellular pathways and processes regulating MRC1. This work lays the groundwork for identifying specific genes and regulatory networks that regulate MRC1 expression and MRC1-mediated endocytosis in macrophages. SIGNIFICANCE STATEMENT: Macrophages constantly survey and clear tissues by specifically and non-specifically internalizing debris and solutes. However, the molecular mechanisms and modes of regulation of these endocytic and macropinocytic processes are not well understood. Here, CRISPR/Cas9 whole genome screens were used to identify genes regulating uptake of dextran, a sugar polymer that is frequently used as a marker macropinocytosis, and compared with Lucifer yellow, a fluorescent dye with no known receptors. The authors identified the mannose receptor as well as other proteins regulating expression of the mannose receptor as top hits in the screen. Targeted disruption of Mrc1 , the gene that encodes mannose receptor, greatly diminished dextran uptake but had no effect on cellular uptake of Lucifer yellow. Furthermore, exposure to the cytokine IL4 upregulated mannose receptor expression on the cell surface and increased uptake of dextran with little effect on Lucifer yellow uptake. Studies seeking to understand regulation of macropinocytosis in macrophages will be confounded by the use of dextran as a fluid-phase marker. MRC1 is a marker of alternatively activated/anti-inflammatory macrophages and is a potential target for delivery of therapeutics to macrophages. This work provides the basis for mechanistic underpinning of how MRC1 contributes to the receptor-mediated uptake of carbohydrates and glycoproteins from the tissue milieu and distinguishes genes regulating receptor-mediated endocytosis from those regulating the bona fide fluid-phase uptake of fluids and solutes by macropinocytosis.

Journal Article↗
PubMed2026

Gut Microbiota, Lipidome, and Metabolites Mediate Immune Dysregulation in Diabetic Microvascular Disease: A Two-sample Mendelian Randomization and Mediation Analysis.

INTRODUCTION: Diabetic microvascular disease (DMiVD) involves dysregulated immune cell function, but the precise pathogenic mechanisms remain unclear. MATERIALS AND METHODS: We conducted a two-sample Mendelian randomization (MR) study using comprehensive GWAS and FinnGen summary statistics, encompassing 731 immune cell phenotypes, 473 gut microbial taxa, 91 inflammatory proteins, 179 lipid types, 1,400 plasma metabolites, 20 micronutrients, and DMiVD cases. The analysis aimed to evaluate causal associations between these variables and DMiVD. We further explored potential mediating roles of gut microbiota, plasma lipidome, and metabolites using mediation analysis, with multiple sensitivity tests confirming the robustness of our findings. RESULTS: We identified 20 immune cell phenotypes, 33 gut microbial taxa, 31 lipid types, and 83 plasma metabolites with significant causal associations with DMiVD. Mediation analysis revealed that the risk effect of CD3+ resting Tregs on diabetic nephropathy was partly mediated by phosphatidylcholine (16:0_18:2) (10.7%). Additionally, the protective effect of CX3CR1 on monocytes against DMiVD was partly mediated by Unclassified Bacilli A (35%), Species CAG-177 sp003538135 (22.6%), and triacylglycerol (52:6) (25.5%). DISCUSSION: These findings advance understanding of DMiVD pathogenesis, highlighting that modulation of key metabolic pathways and immune regulatory nodes may represent promising therapeutic strategies. Further experimental studies are needed to validate these potential causal relationships. CONCLUSION: Using causal inference approaches, this study identifies immune cell-mediated mechanisms underlying DMiVD, involving gut microbiota, plasma lipids, and metabolites. The results suggest potential intervention targets for mechanistic studies and therapeutic development.

Mendelian Randomization Analysis↗
PubMed1977

Suppression of antibody-mediated and cell-mediated murine immunity by the carcinogen N-[4-(5-nitro-2-furyl)-2-thiazolyl]acetamide.

N-[4-(5-Nitro-2-furyl)-2-thiazolyl]acetamide (NFTA) administered at 1000 ppm in diet to mice for 12 weeks induced a high incidence of lymphocytic leukemia. Effects of NFTA on antibody-mediated immunity and cell-mediated immunity of BALB/c mice were studied using the spleen plaque assay for detection of immunoglobulin M-producing cells and the graft-versus-host (GVH) reaction, respectively. NFTA suppressed both responses. With the spleen plaque assay, the number of antibody-forming cells (AFC) to sheep red blood cells was significantly less than in unmedicated, control mice after treated mice received NFTA at 1000 ppm for 6 days. The GVH reaction was not suppressed at 21 days, but was severely suppressed at 70 days, prior to the histological appearance of leukemia. Effect of dose was studied by administering NFTA at 100, 250, 500, and 1000 ppm of diet for 13 to 14 weeks and then determining the response in the spleen plaque assay and GVH reactions. The ratio of AFC/spleen of NFTA-treated groups to AFC/spleen of an unmedicated control group, at the above specified doses, was 0.86, 0.22, 0.33, and 0.54 in ascending dosage order beginning with 100 ppm. For the GVH reaction, the suppression of the cell-mediated immunity was directly proportional to the dose of NFTA. Suppression of the antibody-mediated immunity in relation to the induction of leukemia at 28 weeks was studied by feeding NFTA at 500 ppm for 14 weeks, followed by unmedicated diet for 14 weeks. During the 11th week, mice were immunized with SRBC; 5 days later the spleens were removed and the spleen plaque assay was performed. Eight of 18 mice fed NFTA developed leukemia. The number of AFC/spleen was 78 X 10(3) +/- 34 for those with leukemia and 68 X 10(3) +/- 24 (p greater than 0.5) for those without leukemia, compared with 170 X 10(3) +/- 74 for the control mice (p less than 0.01 for both groups, compared with controls). A closely related carcinogenic nitrofuran, N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide, did not suppress the antibody-mediated immunity response measured during the 11th week of administration.

Animals↗
PubMed1977

In vitro cell-mediated cytotoxicity in primary biliary cirrhosis and chronic hepatitis. Dysfunction of spontaneous cell-mediated cytotoxicity in primary biliary cirrhosis.

The in vitro cytotoxic function and target cell specificity of peripheral blood lymphocytes from selected patients with primary biliary cirrhosis and hepatitis B surface antigen-negative chronic hepatitis were investigated using 51Cr-labeled human Chang and EL-4 mouse sarcoma cell targets in assays of spontaneous cell-mediated cytotoxicity (SCMC) and mitogen-induced cellular cytotoxicity (MICC). In addition, antibody-dependent cellular cytotoxicity (ADCC) against Chang cells was assessed. At an effector-to-target cell ration of 100:1, the mean SCMC against Chang cells was much less in patients with primary biliary cirrhosis than that in either the controls (P less than 0.001) or the patients with chronic hepatitis (P less than 0.005) whereas the value for patients with chronic hepatitis did not differ significantly from that of the controls. The mean SCMC against EL-4 mouse sarcoma cells was also less in patients with primary biliary cirrhosis than in controls (P less than 0.005) whereas the value for chronic hepatitis was not significantly different from that of the controls or patients with primary biliary cirrhosis. In contrast, MICC against both targets and ADCC against Chang cells were similar for each group. Comparison of SCMC and MICC against both target cells, measured simultaneously, showed similar cytotoxic potenital against both target cells for each group. Effector cells capable of mediating cytotoxicity in each assay were defined by testing the cytotoxic function of lymphocyte subpopulations isolated from two representative patients with each disease using techniques of immunoabsorbent affinity chromatography and Fc receptor binding to antigen-antibody complexes. In both primary biliary cirrhosis and chronic hepatitis SCMC and ADCC were mediated by a subpopulation of lymphocytes which lack surface immunoglobulin (sIg-) and bear Fc receptors (Fc+). In contrast, MICC was mediated by sIg- cells which lack Fc receptors. Lymphocytes bearing sIg- were not cytotoxic in any assay. These results establish a difference in cytotoxic function in primary biliary cirrhosis and chronic hepatitis by defining the presence of a defect in spontaneous cytotoxic function of sIg-, Fc+ lymphocytes against Chang cells in primary biliary cirrhosis.

Adult↗
PubMed1979

Human natural cell-mediated cytotoxicity against fetal fibroblasts. IV. Comparison of cytotoxic activity with antibody-dependent cell-mediated cytotoxicity.

The dependence of human natural killer (NK) cell activity on antibodies was investigated. Absorption of the culture medium with target cells, trypsinization of the effector cells followed by a brief recovery, and incubation of the effector cells in serum-free nutrient medium did not affect natural killer cell activity against fetal fibroblasts. No soluble mediator in the nutrient media of effector cell--fibroblast co-cultures could be demonstrated. It was therefore concluded that antibodies are not involved in the cytolytic activity of natural killer cells. However, competition data and the activity of isolated NK cells against antibody-coated target cells suggested overlapping between the effector cells mediating natural and antibody-dependent cell-mediated cytotoxicity.

Antibody-Dependent Cell Cytotoxicity↗
PubMed2026

Oncolytic HSV-1-Mediated JAG1 Blockade Induces Glioma Senescence-Associated Secretory Phenotype to Increase Macrophage Activation and Cetuximab-Mediated Senolysis.

UNLABELLED: Oncolytic HSV-1 (oHSV) treatment induces Notch signaling and myelosuppression in the tumor microenvironment (TME) of preclinical cancer models. Clinically, the Notch ligand JAG1 was upregulated in patients with recurrent high-grade glioma treated with the oHSV CAN-3110 and correlated with poor prognosis. To better understand endogenous JAG1-mediated signaling in glioma cells and tumor-associated macrophages (TAM), we engineered a JAG1-antagonizing oHSV (OD-0J1) and interrogated its impact on cancer and myeloid cells in the TME. OD-0J1 antagonized JAG1-mediated Notch signaling and suppressed tumor growth in athymic nude and humanized mice, an effect reliant on Notch signaling in tumor cells. Kinome profiling revealed that OD-0J1 treatment suppressed CDK1, resulting in activation of the G2-M cell cycle checkpoint. Cell cycle arrest led to senescence and correlated with increased reactive oxygen species, p62, and autophagosome accumulation and senescence-associated β-galactosidase activity. OD-0J1-induced senescence resulted in increased production of inflammatory chemokines and damage-associated molecular patterns (DAMP), such as IL1β, HMGB1, and extracellular ATP. Coculturing macrophages with OD-0J1-infected tumor cells led to stimulation of chemotactic and proinflammatory pathways, as well as increased Fc receptor activation. Single-cell RNA sequencing and flow cytometric analysis of F4/80+ cells isolated from tumors showed a shift from tumor-supporting TAMs to inflammatory macrophages upon OD-0J1 treatment. Heightened EGFR activation in senescent cells was a mechanism to escape cell death, which created a unique opportunity for cetuximab as a senolytic agent. Combination therapy reduced EGFR signaling and induced macrophage-mediated antibody-dependent cellular cytotoxicity, thereby increasing the antitumor therapeutic efficacy of OD-0J1. SIGNIFICANCE: Leveraging JAG1 antagonism in the context of oncolytic virotherapy rewires macrophage polarization within the tumor microenvironment, which has wide implications for sensitizing tumors to antibodies, senolytic agents, and BiTE therapies.

Humans↗
PubMed1979

Antibody-dependent cell-mediated cytotoxicity (ADCC) and cell-mediated cytotoxicity (CMC) to HBsAg-coated target cells in patients with hepatitis B and chronic hepatitis (CAH).

A new technique using HBsAg-coated Chang cells as target cells was developed in order to measure cell-mediated immune reactions to HBsAg. The specificity of cytotoxic reactions was tested in experiments using Chang cells conjugated with human serum albumin. Antibody-dependent cell-mediated cytotoxicity (ADCC) specific for the HBsAg-coated target cells was demonstrated up to dilutions of anti-HBsAg serum of 10,000 : 1, when lymphocytes from the peripheral blood of normal individuals were added to the target cells. Spontaneous cell-mediated cytotoxicity (CMC) to HBsAg-coated target cells was demonstrated for lymphocytes from patients with hepatitis B and from patients with chronic active hepatitis (CAH), but not for lymphocytes from healthy controls. The CMC of hepatitis B lymphocytes to HBsAg-coated target cells was inhibited in the presence of antiserum to HBsAg. In experiments using purified lymphocyte populations evidence is presented that the CMC is T-cell dependent. HLA-restriction of the CMC was not observed. The described cytotoxicity test system has the advantage that target cells conjugated with defined antigens are used and that relevant control target cells are available.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1976

Cell-mediated immunity to Friend virus-induced leukemia. II. Characteristics of primary cell-mediated cytotoxic response.

The primary cell-mediated cytotoxic response to a Friend virus-induced leukemia, FBL-3, in C57BL/6 mice was measured by the 125IUdR release assay. Intraperitoneal (i.p.) inoculation of 1 x 10(1) FBL-3 cells produced progressive tumor growth (progressors); subcutaneous (s.c.) inoculation of as many as 5 x 10(6) FBL-3 cells produced only transient tumor growth (regressors), and these mice would subsequently resist i.p. challenge of FBL-3 cells at 3 days after s.c. inoculation. The kinetics of the primary cell-mediated cytotoxic response of regressors was biphasic. Significant cytotoxicity could be detected at 3 to 5 days after s.c. inoculation of 5 x 10(6) FBL-3 cells peaked at days 10 to 14, declined to a very low level or became undetectable around days 20 to 30; then the reactivity reappeared and persisted at least up to 60 days. In progressors, the kinetics of the cell-mediated cytotoxic response was similar to the regressors, but the reactivity was much lower. The cytotoxic response was found to be T cell dependent, during both the first peak (days 10 to 14) and the second peak (days 40 to 60). In adoptive transfer experiments, lymphocytes from regressors gave 90% protection against i.p. challenge of FBL-3; lymphocytes from progressors only gave 40% protection.

Animals↗
PubMed1976

Cell-mediated immunity to Friend virus-induced leukemia. III. Characteristics of secondary cell-mediated cytotoxic response.

By employing the 125IUdR release cytotoxicity assay, we have been able to measure the primary and secondary cell-mediated cytotoxic response of C57BL/6 mice to FBL-3 cells, a syngeneic Friend virus-induced leukemia. It was found that the secondary cell-mediated cytotoxic response occurred more rapidly after challenge (within 3 days) than the primary response, and the levels of reactivity were considerably higher. As in the primary response, the secondary cytotoxic reactivity of spleen cells was T cell dependent, being eliminated by pretreatment with anti-theta antibody plus complement. However, the secondary reactivity of pertioneal exudate (PE) cells was not entirely T-cell dependent. The specificity of the secondary cytotoxic response was analyzed by primary or secondary immunization with various tumor cells and by testing of cytotoxic lymphocytes against a variety of target cells. When spleen cells were used for testing, only tumor cells induced by Friend, Moloney, or Rauscher (FMR) leukemia viruses could produce secondary cell-mediated cytotoxic responses against FBL-3 cells. This correlated well with the specificity observed in the in vivo tumor transplantation protection studies. Similarly, spleen cells immune to FBL-3 had appreciable cytotoxicity against tumor cells induced by FMR viruses. The FBL-3 immune mice also gave significant protection against the challenge of FMR leukemias. When PE cells were used for testing, they gave higher levels of cytotoxicity against tumor cells induced by FMR viruses, but also gave less, but appreciable, cytotoxicity against non-FMR tumors. The latter reactivity might be related to the antigens induced by the murine endogenous type C viruses.

Animals↗
PubMed1978

Effect of BCG on alloimmune cell-mediated cytotoxicity in (C57BL/6Jfemale x A/Jmale)F1 mice. I. Effect of different BCG treatments on cytotoxicity mediated by T-cells and macrophages.

The effect of BCG on the development of cell-mediated cytotoxicity (CMC) in the spleens of allogeneic tumor-bearing female (C57BL/6Jfemale x A/Jmale)F1 mice was studied. BCG-treated tumor-bearing animals elicited a stronger CMC response than did the untreated tumor-bearing animals. Furthermore, the degree of activation was dependent on the time, route of injection, and dose of BCG. Therefore, if the BCG was administered at suboptimal conditions, a less marked stimulation of the CMC resulted. A combination of a high BCG dose given iv 12 days before implant of P815 tumor cells and a low, second dose given at the time of implant produced the most marked activation of the CMC response. By the use of in vitro technique, the specific CMC was mediated mostly by T-cells, with macrophages making a less significant contribution.

Animals↗
PubMed2025

EP300-mediated lactylation leads to ulcerative colitis via CD86-positive plasmacytoid dendritic cells: A Mendelian randomization and mediation analysis.

This study explores the potential mechanism between lactylation and ulcerative colitis (UC) using two-sample Mendelian randomization and multi-omics analysis. This study employed expression quantitative trait loci and protein quantitative trait loci as exposures, with UC from the Finnish database as the outcome, to conduct Mendelian randomization analysis on lactylation-related target genes, aiming to investigate the causal relationships between these exposures and the outcome. Sensitivity and pleiotropy tests, combined with colocalization analysis, are performed to identify the best target genes and ensure the robustness of the results. Finally, immune cells are included for mediation analysis between lactylation and UC to explore potential mechanisms of action. Through Mendelian randomization analysis combined with sensitivity and pleiotropy tests, 2 lactylation target genes were found to have a significant causal relationship with UC. Subsequent colocalization analysis confirmed EP300 as a potential gene target. After including immune cells in the mediation analysis, it was discovered that there is a potential mechanism involving EP300, CD86+ plasmacytoid dendritic cells (pDCs), and UC. There is a significant causal relationship between lactylation and UC. Furthermore, the lactylation-modified gene EP300 may lead to UC occurrence by regulating CD86+ pDCs.

Humans↗
PubMed1975

A comparison of the effector cells involved in cell-mediated lympholysis and antibody-dependent cell-mediated cytotoxicity in man.

Some physical and mechanistic properties of cytotoxic lymphocytes and antibody-dependent killer cells were compared. Cytotoxic lymphocytes were measured by the cell-mediated lympholysis (CML) technique after sensitization of human peripheral blood leukocytes (PBL) in unidirectional mixed leukocyte culture (MLC). Killer cells were measured before and after MLC in an antibody-dependent cell-mediated cytotoxicity (ADCMC) assay using 51-Cr-labeled mouse mastocytoma cells as targets. Quantitative analysis of the cytotoxic activity of populations separated by velocity sedimentation at 1 g indicated that cytotoxic lymphocytes in MLC were a relatively heterogeneous population of rapidly sedimenting cells that corresponded morphologically to lymphoblasts. Further studies in which PBL were separated before MLC suggested that such cytotoxic lymphocytes were derived from small lymphocyte progenitors. Analysis of ADCMC in separated populations showed that most killer cells in PBL had the sedimentation properties of small lymphocytes. After stimulation of PBL in MLC, increased ADCMC activity was detected, and the increased activity was associated with a population of rapidly sedimenting cells, Comparison of the sensitivity of cytotoxic lymphocytes and killer cells to inhibition by EDTA, cytochalasin B, and dimethyl sulfoxide showed no significant differences between the two types of effector cells.

Cell Separation↗
PubMed1978

Cytotoxicity of human peripheral lymphocytes in cell-mediated lympholysis; antibody-dependent cell-mediated lympholysis and natural cytotoxicity assays after mixed lymphocyte culture.

Lymphocytes that have been purified by Ficoll-Hypaque centrifugation lose antibody-dependent and natural cytotoxic activities upon culture in tissue culture medium supplemented with human plasma. However, stimulation of peripheral lymphocytes in the mixed leukocyte culture (MLC) appears to enhance killer (K) and natural killer (NK) activities in addition to generating cytotoxic T ymphocytes. Enhancement of NK and antibody dependent activities appears to correlate with cell division as measured by 3H-thymidine uptake. However, elimination of dividing cells in the MLC by addition of 5-bromodeoxyuridine has no effect on NK and K cells activities. Since this treatment abolishes cell-mediated lympholysis mediated by cytotoxic T lymphocytes, it is a useful probe for determining the relative activities of NK, K, and cytotoxic T lymphocyte effector cells after lymphocyte stimulation.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1977

A model for distinguishing between beta1-receptors which mediate a specific effect on the heart rate and those which mediate a positively inotropic effect.

The study was conducted in six healthy male volunteers aged between 20 and 30 years. Cardiac output was determined by means of the Swan-Ganz-thermodilution-method. A control-study was carried out, during which an isoproterenolinfusion with increasing doses was given. Fifty minutes after i.v. injection of a beta-receptor-blocker the hemodynamic parameters were measured again under increasing doses of isoproterenol until the block was overcome. This study procedure was performed twice in each subject at an interval of at least 14 days. For the one study 15 mg propranolol i.v. and for the other 0,5 mg mepindolol i.v., a new beta-receptor-blocker, were injected. After i.v. injection of propranolol the dose-response-relationship-curve for the heart-rate (HR) and stroke volume (SV) describes a definite shift to the right. After mepindolol the dose-effect curve for the heart rate describes a definite shift to the right, as seen with propranolol. In contrast, only a very slight shift can be seen in respect of the SV increase, i.e. the SV and HR curves dissociate under mepindolol. The results of our study indicate, that a distinction can be made with respect to the so-called beta 1-receptors between those mediating a specific effect on the heart-rate and those mediating a mainly positive inotropic effect.

Adrenergic beta-Antagonists↗
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↗
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↗