RESUMEN
The COVID-19 pandemic and the associated mitigation measures to reduce the spread of disease affected the social, economic, and overall health of individuals. Quantitative administrative datasets typically did not contain demographic information that allowed for reporting or analysis of the impacts of COVID-19 on people living with disabilities. Understanding the experiences of this population during the pandemic can inform the design of public health responses that are more robust and better connected to community. This paper describes a qualitative participatory study with a diverse sample of people living with disabilities in King County, WA. Through 2 listening sessions and 35 semi-structured interviews, it examines what impacts COVID-19 brought for people living with disabilities; elucidates the supports that were helpful in addressing COVID-19 impacts; examines inequities faced by the disability community; and sheds light on how to engage with this community to inform the public health emergency response. The process, protocols, findings, and lessons learned are replicable by other local health departments and could be incorporated as part of routine data collection and considered for future public health emergencies.
Asunto(s)
COVID-19 , Personas con Discapacidad , COVID-19/epidemiología , Humanos , Pandemias , Investigación Cualitativa , Washingtón/epidemiologíaRESUMEN
Research partnerships between universities and communities following the principles of community-based participatory research (CBPR) have the potential to eliminate cycles of health disparities. The purpose of this article is to describe the process of establishing a community-campus network with a distinct mission and vision of developing trusting and successful research partnerships that are sustained and effective. In 2019, Morgan CARES was established to facilitate community engagement by founding a community center "within" a low-income residential neighborhood as a safe and accessible hub for creating a vibrant learning community. A community needs assessment and asset mapping was conducted and several necessary resources and services were provided to maximize networking opportunities, nurture innovative ideas and proposals, and provide seed funding. Lessons learned informed the optimization of a theoretical model that has guided the development and implementation of the program's key components. By December 2021, Morgan CARES had recruited 222 community and 137 academic members representing diverse expertise from across Baltimore City. We also successfully established new partnerships and funded a total of 17 small community-academic awards. Although in its early stages, Morgan CARES has established a dynamic learning community following a conceptual framework that could guide future similar initiatives.
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Creación de Capacidad , Relaciones Comunidad-Institución , Investigación Participativa Basada en la Comunidad , Características de la Residencia , UniversidadesRESUMEN
Mouse Hepa1-6 hepatocellular carcinoma (HCC) cells were transduced with the membrane form of macrophage colony stimulating factor (mM-CSF). When mM-CSF transduced Hepa1-6 cells were injected subcutaneously into mice, these cells did not form tumors. The spleens of these immunized mice contained cytotoxic CD8+ T lymphocytes (CTL) that killed the unmodified Hepa1-6 cells. We show that the alternative form of macrophage colony stimulating factor (altM-CSF) induced CTL-mediated immunity against Hepa1-6 cells. AltM-CSF is restricted to the H-2D(b) allele. CTLs killed RMA-S cells loaded with exogenous altM-CSF peptide. Vaccination of mice with dendritic cells pulsed with the altM-CSF peptide stimulated anti-Hepa1-6 CTLs. Hyper-immunization of mice with mM-CSF Hepa1-6 cells showed inflammation of the liver and kidneys. Although altM-CSF was expressed within liver and kidney cells, its intensity was lower than Hepa1-6 cells. AltM-CSF was detected within the human HepG2 cell line. These studies suggest that altM-CSF may be a tumor antigen for HCC.
Asunto(s)
Neoplasias Hepáticas Experimentales/inmunología , Factor Estimulante de Colonias de Macrófagos/inmunología , Linfocitos T Citotóxicos/inmunología , Animales , Antígenos de Neoplasias/inmunología , Linfocitos T CD8-positivos/inmunología , Línea Celular Tumoral , Pruebas Inmunológicas de Citotoxicidad , Ensayo de Inmunoadsorción Enzimática , Citometría de Flujo , Humanos , Inmunización , Inmunohistoquímica , Neoplasias Hepáticas Experimentales/genética , Neoplasias Hepáticas Experimentales/prevención & control , Factor Estimulante de Colonias de Macrófagos/administración & dosificación , Factor Estimulante de Colonias de Macrófagos/biosíntesis , Factor Estimulante de Colonias de Macrófagos/genética , Ratones , Ratones Endogámicos C57BL , Microscopía Fluorescente , Isoformas de Proteínas , ARN/química , ARN/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transducción GenéticaRESUMEN
Macrophage colony stimulating factor (M-CSF, also called colony stimulating factor-1) has traditionally been viewed as a growth/differentiation factor for monocytes, macrophages, and some female-specific tumors. As a result of alternative mRNA splicing and post-translational processing, several forms of M-CSF protein are produced: a secreted glycoprotein, a longer secreted form containing proteoglycan, and a short membrane-bound isoform. These different forms of M-CSF all initiate cell signaling in cells bearing the M-CSF receptor, called c-fms. Here we review the biology of M-CSF, which has important roles in bone physiology, the intestinal tract, cancer metastases to the bone, macrophage-mediated tumor cell killing and tumor immunity. Although this review concentrates mostly on the membrane form of human M-CSF (mM-CSF), the biology of the soluble forms and the M-CSF receptor will also be discussed for comparative purposes. The mechanisms of the biological effects of the membrane-bound M-CSF reveal that this cytokine is unexpectedly involved in many complex molecular events. Recent experiments suggest that a tumor vaccine based on membrane-bound M-CSF-transduced tumor cells, combined with anti-angiogenic therapy, should be evaluated further for use in clinical trials.
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Factor Estimulante de Colonias de Macrófagos/fisiología , Macrófagos/fisiología , Transducción de Señal/fisiología , Epítopos de Linfocito T/inmunología , Glioma/patología , Humanos , Intestinos/citología , Activación de Macrófagos , Monocitos/fisiología , VacunaciónRESUMEN
PURPOSE: Allogeneic glioma cell lines that are partially matched to the patient at class I human leukocyte antigen (HLA) loci and that display tumor-associated antigens (TAA) or antigenic precursors [tumor antigen precursor proteins (TAPP)] could be used for generating whole tumor cell vaccines or, alternatively, for extraction of TAA peptides to make autologous dendritic cell vaccines. EXPERIMENTAL DESIGN: Twenty human glioma cell lines were characterized by molecular phenotyping and by flow cytometry for HLA class I antigen expression. Twelve of the 20 cell lines, as well as analyses of freshly resected glioma tissues, were further characterized for protein and/or mRNA expression of 16 tumor antigen precursor proteins or TAA. RESULTS: These 20 human glioma cell lines potentially cover 77%, 85%, and 78% of the U.S. Caucasian population at HLA-A, HLA-B, and HLA-C alleles, respectively. All cells exhibited multiple TAA expressions. Most glioma cells expressed antigen isolated from immunoselected melanoma-2 (Aim-2), B-cyclin, EphA2, GP100, beta1,6-N-acetylglucosaminyltransferase V (GnT-V), IL13Ralpha2, Her2/neu, hTert, Mage, Mart-1, Sart-1, and survivin. Real-time PCR technology showed that glioblastoma specimens expressed most of the TAA as well. Tumor-infiltrating lymphocytes and CD8(+) CTL killed T2 cells when loaded with specific HLA-A2(+) restricted TAA, or gliomas that were both HLA-A2(+) and also positive for specific TAA (Mart-1, GP100, Her2/neu, and tyrosinase) but not those cells negative for HLA-A2 and/or lacking the specific epitope. CONCLUSIONS: These data provide proof-in-principle for the use of allogeneic, partially HLA patient-matched glioma cells for vaccine generation or for peptide pulsing with allogeneic glioma cell extracts of autologous patient dendritic cells to induce endogenous CTL in brain tumor patients.
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Antígenos/biosíntesis , Antineoplásicos/farmacología , Neoplasias Encefálicas/inmunología , Células Dendríticas/citología , Glioma/inmunología , Glioma/terapia , Inmunoterapia/métodos , Neoplasias Encefálicas/terapia , Línea Celular Tumoral , Citometría de Flujo , Genes MHC Clase I , Antígenos HLA/biosíntesis , Humanos , Inmunoterapia/instrumentación , Microscopía Fluorescente , Fenotipo , Trasplante HomólogoRESUMEN
Human U251MG glioma cells retrovirally transduced with the human gene for the membrane form of macrophage colony-stimulating factor (mM-CSF) were investigated. The clones, MG-2F11 and MG-2C4, that expressed the most mM-CSF, but not the viral vector or the parental U251MG cells, were killed by both murine and human monocyte/macrophages in cytotoxicity assays. MG-2F11 cells failed to form subcutaneous tumors in either nude or NIH-bg-nu-xidBR mice, while mice inoculated with the U251MG viral vector (MG-VV) cells developed tumors. Electron microscopy studies showed that 4 hours after subcutaneous injection, the mM-CSF-transduced cells began dying of a process that resembled paraptosis. The dying tumor cells were swollen and had extensive vacuolization of their mitochondria and endoplasm reticulum. This killing process was complete within 24 hours. Macrophage-like cells were immediately adjacent to the killed MG-2F11 cells. Immunohistological staining for the heat shock proteins HSP60, HSP70 and GRP94 (gp96) showed that 18 hours after inoculation into nude mice, the MG-2F11 injection site was two to four times more intensely stained than the MG-VV cells. This study shows that human gliomas transduced with mM-CSF have the potential to be used as a safe live tumor cell vaccine.
Asunto(s)
Apoptosis , Chaperonina 60/metabolismo , Glioma/metabolismo , Proteínas HSP70 de Choque Térmico/metabolismo , Factor Estimulante de Colonias de Macrófagos/genética , Proteínas de la Membrana/metabolismo , Monocitos/fisiología , Animales , Citotoxicidad Inmunológica , Retículo Endoplásmico/metabolismo , Expresión Génica/fisiología , Glioma/patología , Humanos , Técnicas In Vitro , Factor Estimulante de Colonias de Macrófagos/metabolismo , Membranas , Ratones , Ratones Mutantes , Ratones Desnudos , Mitocondrias/metabolismo , Transducción Genética , Células Tumorales Cultivadas , Vacuolas/metabolismoRESUMEN
Human U251 and D54 glioma cells were tested for expression of 25 glioma-associated tumor antigen precursor proteins (TAPP) under hypoxic (1% O(2)) or normoxic (21% O(2)) conditions. Hypoxic glioma cell lines increased their mRNA expression for nine TAPP (Aim2, Art-4, EphA2, EZH2, Fosl1, PTH-rP, Sox 11, Whsc2 and YKL-40), as assessed by quantitative reverse transcriptase real-time/polymerase chain reaction (qRT-PCR). Increased differences with three hypoxic-induced TAPP: EZH2, Whsc2 and YKL-40 were shown at the protein levels by fluorescent antibody staining and quantitative electrophoretic analysis. Two TAPP (MRP3 and Trp1) were down-regulated by hypoxia in glioma cell lines. Growing the glioma cells under hypoxia for 13 days, followed by returning them back to normoxic conditions for 7 days, and restored the original normoxic TAPP profile. Thus, hypoxia was an environmental factor that stimulated the transient expression of these antigens. Intracranial xenografts grown in nude mice derived from U251 cells that had been cultured under neurosphere stem cell conditions showed increased expression of Whsc2 or YKL-40, demonstrating that these in vitro properties of glioma also occur in vivo. Whsc2-specific cytotoxic T lymphocytes killed the hypoxic U251 glioma cells better than normoxic glioma cells. The antigens expressed by hypoxic tumor cells may be a better source of starting tumor material for loading dendritic cells for novel immunotherapy of glioma using tumor-associated antigens.
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Antígenos de Neoplasias/biosíntesis , Neoplasias Encefálicas/inmunología , Glioma/inmunología , Hipoxia , Antígeno AC133 , Animales , Antígenos CD/biosíntesis , Antígenos de Neoplasias/metabolismo , Neoplasias Encefálicas/patología , Línea Celular Tumoral , Citometría de Flujo/métodos , Glioma/patología , Glicoproteínas/biosíntesis , Humanos , Subunidad alfa del Factor 1 Inducible por Hipoxia/biosíntesis , Ratones , Ratones Desnudos , Microscopía Fluorescente/métodos , Trasplante de Neoplasias , Oxígeno/metabolismo , Péptidos/química , Reacción en Cadena de la Polimerasa/métodos , ARN Mensajero/metabolismo , Linfocitos T Citotóxicos/citologíaRESUMEN
Paraptosis is the programmed cell death pathway that leads to cellular necrosis. Previously, rodent and human monocytes/macrophages killed glioma cells bearing the membrane macrophage colony stimulating factor (mM-CSF) through paraptosis, but the molecular mechanism of this killing process was never identified. We have demonstrated that paraptosis of rat T9 glioma cells can be initiated through a large potassium channel (BK)-dependent process initiated by reactive oxygen species. Macrophage mediated cytotoxicity upon the mM-CSF expressing T9-C2 cells was not prevented by the addition of the caspase inhibitor, zVAD-fmk. By a combination of fluorescent confocal and electron microscopy, flow cytometry, electrophysiology, pharmacology, and genetic knock-down approaches, we demonstrated that these ion channels control cellular swelling and vacuolization of rat T9 glioma cells. Cell lysis is preceded by a depletion of intracellular ATP. Six-hour exposure to BK channel activation caused T9 cells to over express heat shock proteins (Hsp 60, 70, 90 and gp96). This same treatment forced HMGB1 translocation from the nuclear region to the periphery. These last molecules are "danger signals" that can stimulate immune responses. Similar inductions of mitochondrial swelling and increased Hsp70 and 90 expressions by BK channel activation were observed with the non-immunogenic F98 glioma cells. Rats injected with T9 cells which were killed by prolonged BK channel activation developed immunity against the T9 cells, while the injection of x-irradiated apoptotic T9 cells failed to produce the vaccinating effect. These results are the first to show that glioma cellular death induced by prolonged BK channel activation improves tumor immunogenicity; this treatment reproduces the vaccinating effects of mM-CSF transduced cells. Elucidation of strategies as described in this study may prove quite valuable in the development of clinical immunotherapy against cancer.
Asunto(s)
Apoptosis , Vacunas contra el Cáncer/administración & dosificación , Adenosina Trifosfato/metabolismo , Animales , Apoptosis/efectos de los fármacos , Vacunas contra el Cáncer/inmunología , Línea Celular Tumoral , Membrana Celular/metabolismo , Retículo Endoplásmico/metabolismo , Técnicas de Silenciamiento del Gen , Canales de Potasio de Gran Conductancia Activados por el Calcio/metabolismo , Macrófagos/metabolismo , Microscopía Confocal , Microscopía Electrónica , Mitocondrias/metabolismo , Dilatación Mitocondrial , Péptidos/farmacología , Floretina/metabolismo , Ratas , Especies Reactivas de Oxígeno/metabolismoRESUMEN
The response of human peripheral blood mononuclear cells (PBMC) to cloned human HLA-A2+ U251 glioma cells (U251-2F11/TK) expressing membrane macrophage colony stimulating factor (mM-CSF) was investigated in vitro and in vivo. Enriched human monocytes derived from cancer patients produced a respiratory burst following 20min of interaction with mM-CSF expressing U251 glioma cells. This respiratory burst response was not observed in the enriched human monocytes following similar exposure to the viral vector control U251 (U251-VV) cells. Reactive oxygen species such as H(2)O(2) and HOCl produced death of the U251 cells. The U251-2F11/TK cells failed to grow in severely compromised combined immunodeficient (NIH-bg-nu-xidBR) mice that were depleted of murine monocyte/macrophages then reconstituted with human HLA-A2+ PBMC. Reactive oxygen species (ROS) were produced by PBMC, both in vitro and in vivo in response tomM-CSF expressing U251 cells. U251-2F11/TK cells failed to form subcutaneous tumors in macrophage depleted mice reconstituted with human PBMC; whereas, progressive growth of such tumors was observed with the U251-VV cells. U251-2F11/TK tumors formed if the initial inoculums of PBMC were depleted of monocytes. From this work it can be concluded that mM-CSF transduced U251-2F11/TK glioma cells can safely stimulate human innate immune responses in vivo.
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Glioma/inmunología , Inmunidad Innata , Factor Estimulante de Colonias de Macrófagos/biosíntesis , Monocitos/inmunología , Monocitos/metabolismo , Animales , Línea Celular Tumoral , Glioma/metabolismo , Glioma/patología , Humanos , Técnicas In Vitro , Linfocitos Infiltrantes de Tumor/inmunología , Factor Estimulante de Colonias de Macrófagos/genética , Ratones , Ratones Desnudos , Ratones SCID , Trasplante de Neoplasias , Especies Reactivas de Oxígeno/metabolismo , Proteínas Recombinantes/biosíntesis , Proteínas Recombinantes/genética , Estallido Respiratorio , Transducción Genética , Trasplante HeterólogoRESUMEN
In this study, human monocytes/macrophages were observed to kill human U251 glioma cells expressing membrane macrophage colony-stimulating factor (mM-CSF) via a swelling and vacuolization process called paraptosis. Human monocytes responded to the mM-CSF-transduced U251 glioma cells, but not to viral vector control U251 glioma cells (U251-VV), by producing a respiratory burst within 20 min. Using patch clamp techniques, functional big potassium (BK) channels were observed on the membrane of the U251 glioma cell. It has been previously reported that oxygen indirectly regulates BK channel function. In this study, it was demonstrated that prolonged BK channel activation in response to the respiratory burst induced by monocytes initiates paraptosis in selected glioma cells. Forced BK channel opening within the glioma cells by BK channel activators (phloretin or pimaric acid) induced U251 glioma cell swelling and vacuolization occurred within 30 min. U251 glioma cell cytotoxicity, induced by using BK channel activators, required between 8 and 12 h. Swelling and vacuolization induced by phloretin and pimaric acid was prevented by iberiotoxin, a specific BK channel inhibitor. Confocal fluorescence microscopy demonstrated BK channels co-localized with the endoplasmic reticulum and mitochondria, the two targeted organelles affected in paraptosis. Iberiotoxin prevented monocytes from producing death in mM-CSF-expressing U251glioma cells in a 24 h assay. This study demonstrates a novel mechanism whereby monocytes can induce paraptosis via the disruption of internal potassium ion homeostasis.
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Muerte Celular/inmunología , Glioma/inmunología , Canales de Potasio de Gran Conductancia Activados por el Calcio/metabolismo , Factor Estimulante de Colonias de Macrófagos/metabolismo , Monocitos/metabolismo , Línea Celular Tumoral , Cartilla de ADN , Diterpenos/farmacología , Electrofisiología , Homeostasis/inmunología , Humanos , Canales de Potasio de Gran Conductancia Activados por el Calcio/antagonistas & inhibidores , Activación de Macrófagos/inmunología , Microscopía Fluorescente , Modelos Biológicos , Monocitos/efectos de los fármacos , Monocitos/inmunología , Péptidos/farmacología , Floretina/farmacología , Potasio/metabolismo , Interferencia de ARN , Estallido Respiratorio/inmunología , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Factores de TiempoRESUMEN
Combining a T9/9L glioma vaccine, expressing the membrane form of M-CSF, with a systemic antiangiogenic drug-based therapy theoretically targeted toward growth factor receptors within the tumor's vasculature successfully treated >90% of the rats bearing 7-day-old intracranial T9/9L gliomas. The antiangiogenic drugs included (Z)-3-[4-(dimethylamino)benzylidenyl]indolin-2-one (a platelet-derived growth factor receptor beta and a fibroblast growth factor receptor 1 kinase inhibitor) and oxindole (a vascular endothelial growth factor receptor 2 kinase inhibitor). A total of 20-40% of the animals treated with the antiangiogenic drugs alone survived, while all nontreated controls and tumor vaccine-treated rats died within 40 days. In vitro, these drugs inhibited endothelial cells from proliferating in response to the angiogenic factors produced by T9/9L glioma cells and prevented endothelial cell tubulogenesis. FITC-labeled tomato lectin staining demonstrated fewer and constricted blood vessels within the intracranial tumor after drug therapy. Magnetic resonance imaging demonstrated that the intracranial T9 glioma grew much slower in the presence of these antiangiogenic drugs. These drugs did not affect in vitro glioma cell growth nor T cell mitogenesis. Histological analysis revealed that the tumor destruction occurred at the margins of the tumor, where there was a heavy lymphocytic infiltrate. Real-time PCR showed more IL-2-specific mRNA was present within the gliomas in the vaccinated rats treated with the drugs. Animals that rejected the established T9/9L glioma by the combination therapy proved immune against an intracranial rechallenge by T9/9L glioma, but showed no resistance to an unrelated MADB106 breast cancer.
Asunto(s)
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Neoplasias Encefálicas/terapia , Glioma/terapia , Inhibidores de la Angiogénesis/administración & dosificación , Inhibidores de la Angiogénesis/farmacología , Animales , Neoplasias Encefálicas/irrigación sanguínea , Neoplasias Encefálicas/inmunología , Neoplasias Encefálicas/mortalidad , Vacunas contra el Cáncer/administración & dosificación , Vacunas contra el Cáncer/inmunología , Línea Celular Tumoral , Células Cultivadas , Sinergismo Farmacológico , Células Endoteliales/citología , Células Endoteliales/efectos de los fármacos , Femenino , Glioma/irrigación sanguínea , Glioma/inmunología , Glioma/mortalidad , Inhibidores de Crecimiento/farmacología , Inhibidores de Crecimiento/uso terapéutico , Inmunohistoquímica , Indoles/farmacología , Indoles/uso terapéutico , Inyecciones Intraperitoneales , Interleucina-2/biosíntesis , Interleucina-2/genética , Linfocitos Infiltrantes de Tumor/patología , Factor Estimulante de Colonias de Macrófagos/administración & dosificación , Factor Estimulante de Colonias de Macrófagos/inmunología , Imagen por Resonancia Magnética , Proteínas de la Membrana/administración & dosificación , Proteínas de la Membrana/inmunología , Oxindoles , ARN Mensajero/biosíntesis , Ratas , Ratas Endogámicas F344 , Receptores de Factores de Crecimiento/antagonistas & inhibidores , Bazo/citología , Bazo/inmunología , Bazo/metabolismoRESUMEN
Cloned T9 glioma cells (T9-C2) expressing the membrane form of macrophage colony stimulating factor (mM-CSF) inoculated subcutaneously into rats do not grow and glioma-specific immunity is stimulated. Immunotherapy experiments showed that intracranial T9 tumors present for one to four days could be successfully eradicated by peripheral vaccination with T9-C2 cells. CD4+ and CD8+ T splenocytes from immunized rats, when restimulated in vitro with T9 cells, produced interleukin-2 and -4. Protective immunity against intracranial T9 gliomas could only be adoptively transferred into naive rats by the CD4+ splenocytes obtained from T9-C2 immunized rats. Rats immunized by the T9-C2 tumor cells also resisted two different syngeneic gliomas (RT2 and F98) but allowed a syngeneic NUTU-19 ovarian cancer to grow. Such cross-protective immunity against unrelated gliomas suggests that mM-CSF transfected tumor cells have immunotherapeutic potential for use as an allogeneic tumor vaccine.
Asunto(s)
Neoplasias Encefálicas/inmunología , Linfocitos T CD4-Positivos/inmunología , Glioma/inmunología , Factor Estimulante de Colonias de Macrófagos/genética , Traslado Adoptivo , Animales , Neoplasias Encefálicas/prevención & control , Neoplasias Encefálicas/ultraestructura , Linfocitos T CD4-Positivos/trasplante , Células Cultivadas , Células Clonales , Femenino , Glioma/prevención & control , Glioma/ultraestructura , Interleucina-2/biosíntesis , Interleucina-2/genética , Interleucina-4/biosíntesis , Interleucina-4/genética , Cinética , Factor Estimulante de Colonias de Macrófagos/metabolismo , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Trasplante de Neoplasias , ARN Mensajero/biosíntesis , Ratas , Ratas Endogámicas F344 , Análisis de Supervivencia , Transfección , Células Tumorales CultivadasRESUMEN
Cloned T9-C2 glioma cells transfected with membrane macrophage colony-stimulating factor (mM-CSF) never formed subcutaneous tumors when implanted into Fischer rats, whereas control T9 cells did. The T9-C2 cells were completely killed within 1 day through a mechanism that resembled paraptosis. Vacuolization of the T9-C2 cell's mitochondria and endoplasmic reticulum started within 4 hours after implantation. By 24 hours, the dead tumor cells were swollen and terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL)-positive. Bcl2-transduced T9-C2 cells failed to form tumors in rats. Both T9 and T9-C2 cells produced cytokine-induced neutrophil chemoattractant that recruited the granulocytes into the tumor injection sites, where they interacted with the tumor cells. Freshly isolated macrophages killed the T9-C2 cells in vitro by a mechanism independent of phagocytosis. Nude athymic rats treated with antiasialo GM1 antibody formed T9-C2 tumors, whereas rats treated with a natural killer cell (NK)-specific antibody failed to form tumors. When treated with antipolymorphonuclear leukocyte (anti-PMN) and antimacrophage antibodies, 80% of nude rats formed tumors, whereas only 40% of the rats developed a tumor when a single antibody was used. This suggests that both PMNs and macrophages are involved in the killing of T9-C2 tumor cells. Immunocompetent rats that rejected the living T9-C2 cells were immune to the intracranial rechallenge with T9 cells. No vaccinating effect occurred if the T9-C2 cells were freeze-thawed, x-irradiated, or treated with mitomycin-C prior to injection. Optimal tumor immunization using mM-CSF-transduced T9 cells requires viable tumor cells. In this study optimal tumor immunization occurred when a strong inflammatory response at the injection of the tumor cells was induced.