HUMORAL IMMUNE ALTERATIONS CAUSED BY LEAD: STUDIES ON AN ADULT TOAD MODEL

There is evidence that environmentalmetal levels affect the immune function. In the particular case of the impact of heavy metals, information available suggests that the immune system is a target for low-dose Pb exposure. Among vertebrates it was shown that amphibians are capable of forming antibodies against a variety of antigens, causing several responses such as anaphylactic response and rejectinggrafts. In this study, the production of antibodies was assessed against sheep red blood cells (SRBC) in the anuran Bufo arenarum after six weekly injections of sublethal doses of lead (50 mg.kg-1, as lead acetate). Natural antibodies (natural heteroagglutinins)were also quantified against SRBC. Both assessments were carried out employing an ELISA method developedto this end, measuring absorbance (A). For natural anti-SRBC antibodies in both control (C) and Pb treated (T) toads, there was a non significant tendency to increase the initial absorbances (C initial: 0.69+0.39 A; T initial: 0.54+0.30 A), relative to those registered at the end of the experiments (C final: 0.89+0.49 A; T final: 0.76+0.31A); the T/C ratios also did not show changes. The only significant difference was found between initial and final samples from lead-treated toads (p Existe evidencia de que los niveles de metal ambientales afectan la funcion inmune. En el caso particular del impacto de metales pesados, la informacion disponible sugiere que el sistema inmune es un blanco para la exposicion a bajas dosis de Pb. Entre los vertebrados, se ha mostrado que los anfibios son capaces de formar anticuerpos contra una variedad de antigenos, que causan diversasrespuestas, tales como respuesta anafilactica y rechazo de injertos. En este estudio, la produccion de anticuerpos fue evaluada contra eritrocitos de oveja (EO) en el anuro Bufo arenarum, luego de seis inyecciones semanales de dosis subletales de plomo (50 mg.kg-1, como acetato de Pb). Los anticuerpos naturales (heteroaglutininas naturales) fueron tambien cuantificados contra EO. Ambas evaluaciones fueron llevadas a cabo empleando un metodo de ELISA desarrollado a este fin, midiendo laabsorbancia (A). Para los anticuerpos anti-EO naturales, tanto en sapos controles (C) como en sapos tratados con Pb (T), hubo una tendencia significativa a incrementar las absorbancias iniciales (C inicial: 0,69+0,39 A; T inicial: 0,54+0,30 A); la relacion T/C tampoco mostro cambios. La unica diferencia significativa se encontro entre las muestras inicial y final de los sapos tratados con plomo (p