RESUMO
An anti-carcinoembryonic antigen (CEA) monoclonal antibody (mAb 6D1. 1) was evaluated in vitro and in vivo to determine its suitability as a tracer for immunoscintigraphy of colorectal carcinomas. Determination of mAb affinity for CEA showed a constant of association of 0.63 +/- 0.11 x 10(9) M-1. Binding of technetium-99m (99mTc)-6D1.1, labeled by a direct method, to human cultured lineages was highly specific. Binding to only CEA-positive LS-174T cells resulted in a saturable curve inhibited by pre-incubation with unlabeled mAb. No binding at all was observed for the human lineages MeWo (melanoma) or ZR75-30 (breast carcinoma), neither of them expressing CEA cells. Intravenous injection of 99mTc-6D1.1 into nude mice xenografted with human LS-174T tumors resulted in planar images of excellent quality. Localization of an irrelevant mAb labeled with either 99mTc or iodine-125 was never observed in tumor masses. Biodistribution studies on excised tumoral tissue showed retention of 28.48% of the injected dose per gram of LS-174T tumor. The tumor-to-blood ratio was 3.46. The same analysis performed on the other three human xenografted tumors studied demonstrated that only the CEA-producing HT-29 (colorectal adenocarcinoma) retained 99mTc-6D1.1 while the other two (ZR75-30 and MeWo) did not. These data demonstrate that this mAb is an adequate tool for targeting CEA-expressing tumors in experimental models.
Assuntos
Anticorpos Monoclonais/análise , Antígeno Carcinoembrionário/imunologia , Carcinoma/diagnóstico por imagem , Neoplasias Colorretais/diagnóstico por imagem , Tecnécio , Animais , Camundongos , CintilografiaRESUMO
An anti-carcinoembryonic antigen (CEA) monoclonal antibody (mAb 6D1.1) was evaluated in vitro and in vivo to determine its suitability as a tracer for immunoscintigraphy of colorectal carcinomas. Determination of mAb affinity for CEA showed a constant of association of 0.63 + or - 0.11 x 109 M-1. Binding of technetium-99m (99mTc)-6D1.1, labeled by a direct method, to human cultured lineages was highly specific. Binding to only CEA-positive LS-174T cells resulted in a saturable curve inhibited by pre-incubation with unlabeled mAb. No binding at all was observed for the human lineages MeWo (melanoma) or ZR75-30 (breast carcinoma), neither of them expressing CEA cells. Intravenous injection of 99mTc-6D1.1 into nude mice xenografted with human LS-174T tumors resulted in planar images of excellent quality. Localization of an irrelevant mAb labeled with either 99mTc or iodine-125 was never observed in tumor masses. Biodistribution studies on excised tumoral tissue showed retention of 28.48 percent of the injected dose per gram of LS-174T tumor. The tumor-to-blood ratio was 3.46. The same analysis performed on the other three human xenografted tumors studied demonstrated that only the CEA-producing HT-29 (colorectal adenocarcinoma) retained 99mTc-6D1.1 while the other two (ZR75-30 and MeWo) did not. These data demonstrate that this mAb is an adequate tool for targeting CEA-expressing tumors in experimental models
Assuntos
Camundongos , Animais , Anticorpos Monoclonais/análise , Antígeno Carcinoembrionário/imunologia , Carcinoma , Neoplasias Colorretais , TecnécioRESUMO
Patients with Humoral immunodeficiency syndromes frequently present recurrent infections, mainly of the digestive and respiratory tracts. This study carried out a clinical and laboratorial evaluation in 15 humoral immunodeficiency patients presenting chronic gastrointestinal symptoms. Out results emphasize the relevance of immunodeficiency syndromes in the differential diagnosis of chronic diarrhea.
Assuntos
Diarreia/etiologia , Síndromes de Imunodeficiência/complicações , Síndromes de Malabsorção/etiologia , Adulto , Criança , Pré-Escolar , Doença Crônica , Feminino , Gastroenteropatias/etiologia , Gastroenteropatias/patologia , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
This study addresses the relevance of colorectal-carcinoma-cell (CRC) CEA expression and degree of differentiation in natural-killer(NK)-mediated lysis susceptibility. A 51Cr-release cytotoxicity assay performed with 5 human CRC lines demonstrated that CRC CEA expression was related to resistance to NK lysis. Moreover, the addition of anti-CEA Fab fragments to the assay led to a significant increase of lysability of high-CEA-producing and NK-resistant cells (LS 174-T), whereas purified CEA drastically reduced lysis of low-CEA-producing and NK-susceptible cells (LISP-I) in a dose-dependent manner. These results strongly suggest that CEA plays a causal role in CRC resistance to NK lysis. Nevertheless, our data did not demonstrate CEA binding to effector cell surface, suggesting that CEA expression can protect CRC, possibly by preventing NK-tumor-cell adhesion to occur. Our results also show that CRC susceptibility to NK lysis was related to a less differentiated phenotype. HCT-8, which are poorly differentiated and low-CEA-producing cells, were cultured in vitro in the presence of the differentiation agent sodium butyrate. Treated cells became less susceptible to NK lysis as they progressed towards a more differentiated phenotype. However, CEA production was not altered upon differentiation. Our study thus demonstrates that both features, CEA expression and degree of cellular differentiation, may individually influence CRC susceptibility to NK lysis.