Impairment of agonist-induced M2 muscarinic receptor activation by autoantibodies from chagasic patients with cardiovascular dysautonomia.

Previous studies showed that circulating autoantibodies against M2 muscarinic receptors (anti-M2R Ab) are associated with decreased cardiac parasympathetic modulation in patients with chronic Chagas disease (CD). Here we investigated whether the exposure of M2R to such antibodies could impair agonist-induced receptor activation, leading to the inhibition of associated signaling pathways. Preincubation of M2R-expressing HEK 293T cells with serum IgG fractions from chagasic patients with cardiovascular dysautonomia, followed by the addition of carbachol, resulted in the attenuation of agonist-induced Gi protein activation and arrestin-2 recruitment. These effects were not mimicked by the corresponding Fab fractions, suggesting that they occur through receptor crosslinking. IgG autoantibodies did not enhance M2R/arrestin interaction or promote M2R internalization, suggesting that their inhibitory effects are not likely a result of short-term receptor regulation. Rather, these immunoglobulins could function as negative allosteric modulators of acetylcholine-mediated responses, thereby contributing to the development of parasympathetic dysfunction in patients with CD.

Systemic administration of imiquimod as an adjuvant improves immunogenicity of a tumor-lysate vaccine inducing the rejection of a highly aggressive T-cell lymphoma.

T-cell lymphomas include diverse malignancies. They are rare, some have low survival rates and they lack curative therapies. The aim of this work was to assess whether employing the TLR7 agonist imiquimod and the T-cell costimulatory molecule CD40 or the combination of both as adjuvants of a cell lysate vaccine could enhance the antitumor immune response using a murine T-cell lymphoma model. Immunization with LBC-lysate and imiquimod protected almost all vaccinated animals. A specific humoral and a Th1-type cellular immunity were induced in mice that rejected the lymphoma, characterized by an elevated number of CD4 + T-cells and secretion of IFN-γ, locally and systemically. In contrast, CD40 alone or in combination with imiquimod did not improve the protective response obtained with LBC-lysate and imiquimod. Systemic administration of imiquimod proved to have high potential to serve as a vaccine adjuvant for the treatment of T-cell lymphomas and was effective in this immunotherapy model.

Cyclophosphamide enhances the release of tumor exosomes that elicit a specific immune response in vivo in a murine T-cell lymphoma.

Exosomes are 60-150 nm small extracellular vesicles (EVs) released by most cells. Tumor-cell-derived exosomes, used as a vaccine, elicit a specific cytotoxic response against tumor cells, usually with a greater immunogenicity than tumor-cell lysates. However, the number of exosomes isolated from culture cells is limited. In recent studies, it was observed that cells respond to different stressor stimuli such as cytotoxic drugs, hypoxia, acidosis, or radiation by increasing the release of EVs. In this study, using the murine LBC T-cell lymphoma, we found that cyclophosphamide significantly increased EVs yield. These EVs express exosome marker proteins such as TSG-101, CD9, CD81, and CD63. Furthermore, similar humoral and cellular immune responses were induced in vivo by EVs isolated from LBC-tumor cells whether they were grown under normal culture conditions (EVs C) or in the presence of cyclophosphamide (EVs CTX). Mice vaccinated either with EVs C or EVs CTX were similarly protected against an intraperitoneal challenge with LBC tumor cells. CD4+ and CD8+ IFN-γ secreting cells were induced in immunized mice and a specific cytotoxic cellular immune response was elicited in vitro. These results demonstrate that a Th1 response was induced by immunization with the EVs. Our findings suggest that treatment of tumor cells with cyclophosphamide is a useful method to enhance the secretion of EVs in sensitive cell lines without altering their antitumor properties and thus may be used to produce antigens for future design of cancer vaccines.

Exosomes Isolated from Ascites of T-Cell Lymphoma-Bearing Mice Expressing Surface CD24 and HSP-90 Induce a Tumor-Specific Immune Response.

Extracellular vesicles (EVs), including endosome-derived nanovesicles (exosomes), are involved in cell-cell communication. Through transfer of their molecular contents, extracellular nanovesicles can alter the function of recipient cells. Due to these characteristics, EVs have shown potential as a new alternative for cancer immunotherapy. Tumor exosomes isolated from malignant ascites can activate dendritic cells, thereby priming the immune system to recognize and kill cancer cells. However, a suppressive role on tumor immune response has also been reported, suggesting that the neoplastic stage of carcinogenesis and the microenvironment where tumor cells grow may influence the amount of EVs released by the cell. This neoplastic stage and microenvironment may also impact EVs' components such as proteins and miRNA, determining their biological behavior. Most T-cell lymphomas have an aggressive clinical course and poor prognosis. Consequently, complementary alternative therapies are needed to improve the survival rates achieved with conventional treatments. In this work, we have characterized EVs isolated from ascites of mice bearing a very aggressive murine T-cell lymphoma and have studied their immunogenic properties. Small EVs were isolated by differential centrifugation, ultrafiltration, and ultracentrifugation at 100,000 × g on a sucrose cushion. The EVs were defined as exosomes by their morphology and size analyzed by electron microscopy, their floating density on a sucrose gradient, as well as their expression of endosome marker proteins ALIX, TSG-101; the tetraspanins CD63, CD9, and CD81. In addition, they contain tumor antigens, the marker for malignancy CD24, the heat shock protein HSP-70, and an unusual surface expression of HSP-90 was demonstrated. The administration of EVs isolated from ascites (EVs A) into naïve-syngeneic mice induced both humoral and cellular immune responses that allowed the rejection of subsequent tumor challenges. However, the immunization had no effect on a non-related mammary adenocarcinoma, demonstrating that the immune response elicited was specific and also it induced immune memory. In vitro analysis demonstrated that T-cells from EVs A-immunized mice secrete IFN-γ in response to tumor stimulation. Furthermore, tumor-specific CD4+ and CD8+ IFN-γ secreting cells could be efficiently expanded from mice immunized with EVs A, showing that a T helper 1 response is involved in tumor rejection. Our findings confirm exosomes as promising defined acellular tumor antigens for the development of an antitumor vaccine.

An Oral Salmonella-Based Vaccine Inhibits Liver Metastases by Promoting Tumor-Specific T-Cell-Mediated Immunity in Celiac and Portal Lymph Nodes: A Preclinical Study.

Primary tumor excision is one of the most widely used therapies of cancer. However, the risk of metastases development still exists following tumor resection. The liver is a common site of metastatic disease for numerous cancers. Breast cancer is one of the most frequent sources of metastases to the liver. The aim of this work was to evaluate the efficacy of the orally administered Salmonella Typhi vaccine strain CVD 915 on the development of liver metastases in a mouse model of breast cancer. To this end, one group of BALB/c mice was orogastrically immunized with CVD 915, while another received PBS as a control. After 24 h, mice were injected with LM3 mammary adenocarcinoma cells into the spleen and subjected to splenectomy. This oral Salmonella-based vaccine produced an antitumor effect, leading to a decrease in the number and volume of liver metastases. Immunization with Salmonella induced an early cellular immune response in mice. This innate stimulation rendered a large production of IFN-γ by intrahepatic immune cells (IHIC) detected within 24 h. An antitumor adaptive immunity was found in the liver and celiac and portal lymph nodes (LDLN) 21 days after oral bacterial inoculation. The antitumor immune response inside the liver was associated with increased CD4(+) and dendritic cell populations as well as with an inflammatory infiltrate located around liver metastatic nodules. Enlarged levels of inflammatory cytokines (IFN-γ and TNF) were also detected in IHIC. Furthermore, a tumor-specific production of IFN-γ and TNF as well as tumor-specific IFN-γ-producing CD8 T cells (CD8(+)IFN-γ(+)) were found in the celiac and portal lymph nodes of Salmonella-treated mice. This study provides first evidence for the involvement of LDLN in the development of an efficient cellular immune response against hepatic tumors, which resulted in the elimination of liver metastases after oral Salmonella-based vaccination.

Design and evaluation of an intravesical delivery system for superficial bladder cancer: preparation of gemcitabine HCl-loaded chitosan-thioglycolic acid nanoparticles and comparison of chitosan/poloxamer gels as carriers.

This study aimed to develop an intravesical delivery system of gemcitabine HCl for superficial bladder cancer in order to provide a controlled release profile, to prolong the residence time, and to avoid drug elimination via urination. For this aim, bioadhesive nanoparticles were prepared with thiolated chitosan (chitosan-thioglycolic acid conjugate) and were dispersed in bioadhesive chitosan gel or in an in situ gelling poloxamer formulation in order to improve intravesical residence time. In addition, nanoparticle-loaded gels were diluted with artificial urine to mimic in vivo conditions in the bladder and were characterized regarding changes in gel structure. The obtained results showed that chitosanthioglycolic acid nanoparticles with a mean diameter of 174.5±3.762 nm and zeta potential of 32.100±0.575 mV were successfully developed via ionotropic gelation and that the encapsulation efficiency of gemcitabine HCl was nearly 20%. In vitro/ex vivo characterization studies demonstrated that both nanoparticles and nanoparticle-loaded chitosan and poloxamer gels might be alternative carriers for intravesical administration of gemcitabine HCl, prolonging its residence time in the bladder and hence improving treatment efficacy. However, when the gel formulations were diluted with artificial urine, poloxamer gels lost their in situ gelling properties at body temperature, which is in conflict with the aimed formulation property. Therefore, 2% chitosan gel formulation was found to be a more promising carrier system for intravesical administration of nanoparticles.

Emerging roles of exosomes in normal and pathological conditions: new insights for diagnosis and therapeutic applications.

From the time when they were first described in the 1970s by the group of Johnstone and Stahl, exosomes are a target of constant research. Exosomes belong to the family of nanovesicles which are of great interest for their many functions and potential for diagnosis and therapy in multiples diseases. Exosomes originate from the intraluminal vesicles of late endosomal compartments named multivesicular bodies and the fusion of these late endosomes with the cell membrane result in the release of the vesicles into the extracellular compartment. Moreover, their generation can be induced by many factors including extracellular stimuli, such as microbial attack and other stress conditions. The primary role attributed to exosomes was the removal of unnecessary proteins from the cells. Now, several studies have demonstrated that exosomes are involved in cell-cell communication, even though their biological function is not completely clear. The participation of exosomes in cancer is the field of microvesicle research that has expanded more over the last years. Evidence proving that exosomes derived from tumor-pulsed dendritic cells, neoplastic cells, and malignant effusions are able to present antigens to T-cells, has led to numerous studies using them as cell-free cancer vaccines. Because exosomes derive from all cell types, they contain proteins, lipids, and micro RNA capable of regulating a variety of target genes. Much research is being conducted, which focuses on the employment of these vesicles as biomarkers in the diagnosis of cancer in addition to innovative biomarkers for diagnosis, prognosis, and management of cardiovascular diseases. Interesting findings indicating the role of exosomes in the pathogenesis of several diseases have encouraged researchers to consider their therapeutic potential not only in oncology but also in the treatment of autoimmune syndromes and neurodegenerative disorders such as Alzheimer's and Parkinson's disease, in addition to infectious diseases such as tuberculosis, diphtheria, and toxoplasmosis as well as infections caused by prions or viruses such as HIV. The aim of this review is to disclose the emerging roles of exosomes in normal and pathological conditions and to discuss their potential therapeutic applications.

Development and evaluation of a novel mucus diffusion test system approved by self-nanoemulsifying drug delivery systems.

The aim of this study was the development of a novel mucus diffusion model and the approval thereof by self-nanoemulsifying drug delivery systems (SNEDDSs). For diffusion experiments, various SNEDD formulations were developed, spiked with fluorescein diacetate, and evaluated for their mucus diffusion behavior through an intestinal mucus layer within the novel setup. In brief, SNEDD formulations resulting in particle sizes of 12.0 nm produced 70.3% of diffused model drug through the mucus layer. In comparison, SNEDDSs with particle sizes of 455.5 nm led to a permeation of 8.3% only. Apart from this size dependence, two SNEDDS excipients namely Cremophor RH 40 and triacetin were identified to strongly affect the permeation through mucus. Hence, it could be demonstrated that particle size and single excipients can positively influence mucus diffusion of SNEDDSs. Furthermore, it could be shown that the developed mucus diffusion model is a promising tool for pharmaceutical research in comparison with already established systems as it allows an easy handling coupled with the possibility to test different kinds of mucus in parallel within one setup.

Preactivated thiomers for vaginal drug delivery vehicles.

It was the purpose of this study to design and evaluate a chitosan derivative as mucoadhesive excipient for vaginal drug delivery systems. The chemical modification of chitosan was achieved by conjugation of thioglycolic acid (TGA) resulting in 1594 µmol thiol groups per gram of polymer followed by the linkage of mercaptonicotinic acid (MNA) to the immobilized thiol groups via disulfide bonding leading to 702 µmol ligand per gram of preactivated polymer. The mucoadhesive properties of these polymers within newly designed vaginal formulations (Chitosan-TGA and Chitosan-TGA-MNA) and commercially available vaginal formulations (Candibene®, Daktarin®, Dalacin®, GynoPevaryl®) were tested over a time period of 24 h via a mucoadhesion test system simulating vaginal conditions, tensile studies and mucus polymer interaction studies via viscosity measurements. Within the vaginal test system simulating vaginal in situ conditions, a 1.5-fold increase in mucoadhesion could be observed for preactivated thiomer formulations after 24 h in comparison to commercially available formulations. Similar results were achieved for tensile studies, as the chitosan-TGA-MNA containing formulation resulted in a 4.9-fold increase in total work of adhesion (TWA) in comparison to Candibene which showed the highest TWA value of all tested commercial formulations. Also in terms of rheology investigations of mucus/formulation mixtures, a 5.8-fold increase in dynamic viscosity for chitosan-TGA-MNA containing mixtures could be observed in comparison to the mucus-free control. In contrast, commercially available formulations achieved a maximum enhancement of 1.9-fold. These outcomes confirm that the newly developed polymer is a promising tool for vaginal drug delivery likely providing a prolonged vaginal residence time due to its comparatively high mucoadhesive properties.

Therapeutic effects of Salmonella typhi in a mouse model of T-cell lymphoma.

In this study, we assessed the effectiveness of a live, attenuated Salmonella enterica serovar Typhi (S. Typhi) vaccine strain as a cancer immunotherapy in a mouse model of metastatic T-cell lymphoma. EL4 tumor-bearing C57BL/6J mice immunized with S. Typhi strain CVD 915, by injection into the tumor and the draining lymph node areas, displayed a significant decrease in tumor growth, a reduction in the mitotic index (MI) of tumors, a delayed development of palpable lymph node metastases and most importantly improved survival, compared to untreated mice. Besides, complete tumor regression was achieved in a small number of bacteria-treated mice. A successful therapeutic response associated with a significant reduction of tumor mass was evident as early as 5 days after treatment. The administration of Salmonella to tumor-bearing mice promoted early cellular infiltration (mainly neutrophils) within the tumor, and was accompanied by a decreased intratumoral interleukin 10 production as well as by leukocyte expansion in tumor draining lymph nodes. A tumor-specific memory immune response was induced in most of cured animals, as evidenced by the lack of tumor growth after a rechallenge with the same tumor. EL4 cells cultured with live Salmonella failed to proliferate and underwent apoptosis in a dose-dependent, time-dependent, and contact-dependent manner. To our knowledge, these results demonstrate for the first time the efficacy of a S. Typhi vaccine strain as an oncolytic and immunotherapeutic agent against a highly malignant tumor and support the use of S. Typhi-based vaccine strains in cancer therapy.

S-protected thiolated chitosan: synthesis and in vitro characterization.

Purpose of the present study was the generation and evaluation of novel thiolated chitosans, so-named S-protected thiolated chitosans as mucosal drug delivery systems. Stability of all conjugates concerning swelling and disintegration behavior as well as drug release was examined. Mucoadhesive properties were evaluated in vitro on intestinal mucosa. Different thiolated chitosans were generated displaying increasing amounts of attached free thiol groups on the polymer, whereby more than 50% of these thiol groups were linked with 6-mercaptonicotinamide. Based on the implementation of this hydrophobic residue, the swelling behavior was 2-fold decreased, whereas stability was essentially improved. Their mucoadhesive properties were 2- and 14-fold increased compared to corresponding thiolated and unmodified chitosans, respectively. Release studies out of matrix tablets comprising the novel conjugates revealed a controlled release of a model peptide. Accordingly, S-protected thiomers represent a promising type of mucoadhesive polymers for the development of various mucosal drug delivery systems.

A novel Salmonella Typhi-based immunotherapy promotes tumor killing via an antitumor Th1-type cellular immune response and neutrophil activation in a mouse model of breast cancer.

We investigated the use of a live, attenuated Salmonella enterica serovar Typhi vaccine strain as an antitumor immunotherapy. Mice bearing a subcutaneous tumor (LM3 mammary adenocarcinoma) were immunized on three occasions with S. Typhi strain CVD 915 by injection into the tumor, the peritumoral tissue and the draining lymph node areas; this procedure was termed Salmonella multiple treatment (Salmonella MT). Tumor-bearing mice subjected to the Salmonella MT exhibited reduced tumor growth, prolonged survival and reduced incidence of lung metastases, compared to untreated mice. We examined the mechanisms mediating this effect and found that Salmonella MT promoted an antitumor Th1-type response characterized by increased frequencies of IFN-γ-secreting CD4(+) T and CD8(+) T cells with reduction of regulatory T cells in tumor draining lymph nodes. The main cells infiltrating bacteria-treated tumors were activated neutrophils, which can exert an antitumor effect through the secretion of TNF-α. These results demonstrate for the first time the efficacy of an attenuated S. Typhi vaccine strain as a cancer immunotherapeutic agent. By potentiating the host antitumor immune response, this approach could be a powerful adjunct tool for cancer therapy.

Complete rejection of a T-cell lymphoma due to synergism of T-cell receptor costimulatory molecules, CD80, CD40L, and CD40.

The equal importance of the qualitative and quantitative characteristics of antigen presentation as well as the set of costimulatory signals provided by antigen presenting cells to T-cells in determining the outcome of T-cell responses at the time of antigen recognition is now clear. Moreover, an important function in innate mechanisms has been recently attributed to costimulatory molecules demonstrating their relevant role in different stages of immune response. In this paper, we demonstrated the ability of CD40L (CD154) and CD80 costimulatory molecules expression in a T-cell lymphoma to induce both T-cell dependent and independent immune responses leading to an important anti-tumor effect. CD40 expression by LBC cells enhanced only T-cell dependent anti-tumor immune response resulting in tumor rejection. Furthermore, this work represents the first report to describe complete tumor rejection after co-inoculation of lymphoma cells transfected with CD40L and CD80 in either presence or absence of CD40 expressing lymphoma cells. In addition, this synergistic effect resulted in long lasting immunity to parental tumor cells. Co-inoculation of tumor cells each genetically modified to express a different costimulatory molecule circumvents the need to co-transfect genetically unstable tumor cells and represents an option for those weakly or non-immunogenic tumors where either treatment alone proved to be inefficient. This strategy represents a promising approach for inducing anti-tumor immunity and provides a new rational design of cancer therapies.

Transgene expression enhancement in T-lymphoma cell lines.

In transfection protocols, the expression levels of the transgene is important to define, still is difficult to obtain in certain cell lines such as those derived from T-lymphoma cells. In this study we evaluate transgene expression kinetics in the presence and absence of two well known transcription activators such as phorbol-12-myristate13-acetate (PMA) and Ionomicin (IO). Three murine T lymphoma cell lines (LBC, EL4 and BW5147) were transfected by electroporation using green fluorescent protein (GFP) as a reporter gene and analyzed by flow cytometry. Addition of PMA/IO resulted in a significant increase of the Mean Fluorescence Intensity but not in GFP-positive cell percentages, either in transient or stable transfected LBC and EL4 cells. Remarkable, BW5147 cells showed low GFP induction with a significant increment only in stable transfected cells. Our results demonstrated that CMV promoter activity can be enhanced in transfected lymphoma cells by PMA/IO suggesting that transgene expression levels can be optimized by means of the use of transcription activators.

IL-2, IL-10, IL-15 and TNF are key regulators of murine T-cell lymphoma growth.

We studied the role of IL-2, IL-15, IL-10, TNF and IL-2 receptor complexes (IL-2R) produced constitutively by a T-cell lymphoma line (LBC) on their own proliferation. The constitutive expression of surface alpha, beta and gamma chains IL-2R was detected in tumor cells by flow cytometry. Using reverse-transcription PCR, mRNA for IL-2, IL-15, IL-10 and TNF were found to be present in LBC. In addition, tumor cells were found to constitutively express intracellular IL-2, IL-15, IL-10 and TNF. Despite the production of these cytokines by tumor cells, specific neutralising antibodies did not inhibit LBC proliferation; surprisingly, anti-IL-15 increased LBC cell growth. We also demonstrated that recombinant IL-2 or IL-15 enhanced LBC cell proliferation. Our data suggest that endogenous IL-2 and IL-15 may trigger the proliferation of lymphoma LBC cells, and so their growth could be regulated, at least partly, by IL-2/IL-15/IL-2R system. In addition, IL-10 and TNF, immunosuppressor and pro-metastatic cytokines, respectively, may promote the in vivo growth of the tumor. The fact that leukaemia-lymphoma cells produce simultaneously both IL-2 and IL-15 should be taken into consideration in the design of immunotherapy protocols directed to IL-2R.

Caracterizacion inmunobiologica de la leucemia murina LB y la linea celular LBC / Immunobiological characterization of the murine LB leukemia and the LBC cell line

El tumor LB se originó como una leucemia linfoide de origen espontáneo. No es inmunogénico y crece rápidamente en el huésped singeneico infiltrando hígado, bazo y ganglíos linfáticos. A partir del tumor original se obtuvo la línea en cultivo LBC, que crece en suspensión, no requiere del agregado de factores de crecimiento y presenta un número modal de cromosomas igual al patrón normal de ratón. La caracterización fenotípica de las células LB y de la línea en cultivo demostró que ambos tipos celulares están constituídos por linfocitos T, CD3-, CD25+, gp 70-, J22d.2+, que expresan antígenos del CMH de clase I pero no de clase II, CD8+, y CD4- en el tumor original pero CD4+ en la línea celular. Esta última fue capaz de inducir una respuesta inmune en el huésped singeneico, mediada por anticuerpos que reaccionaron contra componentesde peso molecular 14, 16 y 27 kDa presentes en las células tumorales y en timocitos pero no en ganglios normales, y por células citotóxicas, efectivas para retardar el tiempo de muerte de los ratones desafiados con el tumor original LB. Por ELISA se pudo comprobar la presencia de receptor soluble de IL-2 en los sueros, ascitis y sobrenadantes de células LB en cultivo, responsable del efecto inhibitorio de la proliferación tumoral. Las células fueron estimuladas por agregado de IL-2 e inhibidas en presencia de un anticuerpo monoclonal específico para IL-2, demostrando la funcionalidad del receptor. Por RT-PCR se puso en evidencia la presencia de ARNn de IL-2 en las células tumorales, confirmando que éstas sintetizan IL-2. Se realizó una triple transfección de las células LBC con los genes que codificam para las cadenas alpha y beta de las moléculas I-A(d) y el gen pSV2-Neo, que confiere resistência al antibiótico Genetecín, y se obtuvieron 3 clones positivos para I-A(d). Por inoculación de estas células se generaron linfocitos T citotóxicos que fueron efectivos para impedir o retrasar significativamente el desarrollo tumoral. En función de estos resultados postulamos que la expresión de antígenos de clase II sobre la superfície celular le confiere a la célula tumoral la capacidad para actuar como célula presentadora de antígenos, generando una respuesta anti-tumoral más eficiente.

Empleo del dot-enzimoinmunoensayo en la valoración de la proteína A de Staphylococcus aureus / Dot-immunobinding assay use in valoration of protein A from Staphylococcus aureus

Se describe un método inmunoenzimático, que, por su gran sensibilidad, permite detectar pequeñas cantidades de proteína A presente en la membrana celular de determinadas cepas de Staphylococcus aureus o la liberada en el medio de cultivo. Esta técnica del dot-enzimoinmunoensayo permite poner en evidencia concentraciones de hasta 0,115 ug.ml-1 de proteína. Comparando los resultados obtenidos con la técnica de inmunodifusión radial, se confirma su mayor sensibilidad y la posibilidad de utilizar un método específico y de fácil realización en el dosaje de proteína A.

Marcadores de superficie y factores humorales en una leucemia murina espontánea / Surface markers and humoral factors in a spontaneous murine leukemia

Se presenta un modelo de linfoma espontáneo en ratones BALB/c que por sus características es apropiado para el estudio de las interacciones entre el tumor y el sistema inmune. La caracterización de las células tumorales se realizó por FACS hecho que permitió determinar que el tumor está constituído por linfocitos T que no expresan proteínas virales gp70 en su membrana y que llevan marcadores de células colaboradoras (CD4) y supresoras (CD8). Además, expresan el receptor para IL-2 y antígenos del complejo mayor de histocompatibilidad de clase I pero no de clase II. No se encuentran anticuerpos en el suero ni en el líquido ascítico de los ratones portadores del tumor (transplante síngeneico); se pudo determinar en estos fluídos la presencia de un factor supresor que inhibió la proliferación de las células tumorales in vitro sí como la respuesta linfoproliferativa a Concavalina A de esplenocitos normales. Los resultados permiten concluir que este modelo experimental puede ser utilizado para el estudio y caracterización de citoquinas que podrían ser responsables del estado de inmunosupresión que se observa en ciertos pacientes con cáncer

Lack of specifici immune response against a spontaneous mouse lymphoma

Se estudió la respuesta inmune inducida por células tumorales, o por extractos de membranas de células tumorales, y la presencia de anticuerpos en el suero de ratones portadores de tumor en un modelo murino. Se demostró la ausencia de anticuerpos en el suero de ratones portadores de tumor. Las células tratadas con Mitomicina C, los extractos de membranas tumorales (TME) y fracciones obtenidos de los mismos (fracción 2) indujeron bajos títulos de anticuerpos específicos cuando se inyectaron en huéspedes singeneicos, mientras que los homogenatos totales de tumor y otras fracciones fueron inefectivas. Los ensayos hechos "in vivo" demostraron que los anticuerpos inducidos no protegían contra las células LB vivas ya que no alteraron el crecimciento del tumor