Evaluation of immunotropic activity of gold nanocolloid in chickens

•Nano-gold affects immune response in chickens.•Effect of nano-gold on immunity depends on dose and duration time.•Long lasting exposure to high doses of gold nanoparticles had a pro-inflammatory effect. Gold nanoparticles (AuNPs) are one of the most examined nanomaterials, but information about their immunogenic potential is still insufficient. Understanding interaction of AuNPs with immune system is essential in designing their safety and possibilities of biomedical applications. An experiment was conducted to determine immunotropic activity of gold nanocolloid (AuNPs) administered orally to chickens depending on dose and duration time. 162 birds were assigned to 9 experimental groups of 18 birds each. The control group (C) did not receive AuNPs. Groups: T10.5, T11.0, T11.5, T12.0, received nano-gold in a rate of 0.5 mg/kg body weight/d, 1.0 mg/kg body weight/d, 1.5 mg/kg body weight/d and 2.0 mg/kg body weight/d in 8–14, 22–28 and 36–42 days of the life. The birds in groups T20.5, T21.0, T21.5, T22.0, received nano-gold in the same doses, but only in 8–10, 22–24 and 36–38 days of life. Phagocytic activity of leukocytes was determined in vitro using Staphylococcus aureus 209P strain, their respiratory burst activity was quantified by nitroblue tetrazolium reduction test. Serum lysozyme content was determined by the turbidimetric method. The Wintrobe method was used to determine the erythrocyte sedimentation rate. Ceruloplasmin in the blood plasma was estimated by the p-phenylenediamine colorimetric method. The level of chicken immunoglobulins: IgA, IgM and IgY and interleukin IL-6 in the blood were determined using ELISA tests. The lowest dose of AuNPs, independently on duration time had no effect on immune parameters of chickens. In all other groups receiving nano-gold for a shorter period (T2), there was an increase in the respiratory burst activity of leukocytes and a drop in lysozyme activity in blood. The higher doses (1.5 and 2.0 mg/kg body weight/d) of the nano-gold administered for the longer time period had a pro-inflammatory effect, as indicated by an increase in the level of interleukin 6 and ceruloplasmin activity as well as the erythrocyte sedimentation rate. They also contributed to an elevation of class IgA and IgY contents in blood. The results of the study revealed that the influence of nano-gold on immune response of chickens were dependent both on dose and duration time. Long lasting administration of higher doses of AuNPs contributed