The
metalloid arsenic and the chlorinated
insecticide endosulfan are common environmental contaminants. Humans, animals, and birds are exposed to these chemicals through water and food. Although health effects due to either
arsenic or
endosulfan exposure are documented, the toxicological impact of co-exposure to these
environmental pollutants is unpredictable and unknown. The present study was undertaken to assess whether concurrent exposure to
arsenic and
endosulfan induces significant alterations in immunological functions. Day-old chicks were exposed to 3.7 ppm of
arsenic via
drinking water and to 30 ppm of
endosulfan-mixed feed either individually or concurrently for up to 60 days. All the chicks were vaccinated with Ranikhet
disease virus (F-strain; RD-F) on days 1 and 30. During the course of study and at term, parameters of cellular and humoral immunity were determined. None of the treatments altered the absolute
body weight or
body weight gain, except
arsenic significantly reduced
weight gain on day 60. Absolute, but not the relative, weights of spleen, thymus and bursa of Fabricius were significantly reduced in all the treatment groups. The
metalloid and
insecticide combination significantly depressed the ability of peripheral blood and splenic lymphocytes to proliferate in response to
antigen RD-F and
mitogen Con A. The delayed type
hypersensitivity response to 2,4-dinitro-1-chlorobenzene or to
PHA-P was also significantly decreased.
Nitric oxide production by RD-F or
lipopolysaccharide-stimulated peripheral blood and splenic mononuclear cells was significantly suppressed following concurrent exposure to
arsenic and
endosulfan. Furthermore, the combined exposure also decreased the antibody response to RD-F. The suppression of cellular and humoral immune responses was also evident following administration of individual compounds, and it was not exacerbated following concurrent exposure. To our knowledge, this is the first report describing the suppression of immune responses following exposure to
arsenic alone or in combination with
endosulfan at environmentally realistic concentrations in avian species. Therefore, immunotoxicological effects induced by concurrent exposure to
arsenic and chlorinated pesticides should be considered when assessing the risk to human and animal health.