Effect of Nonasilica on Immune Responses in Wistar Rats^a

A total of 35 apparently healthy Wistar rats, aged 6 weeks, of both sexes were randomly divided in two groups i.e. group I with 20 rats and group II with 15 rats. Group I was kept as control whereas group II was orally administered silicon dioxide (silica) nanoparticles of 20 nm diameter in distilled water. The Silica nanoparticles were administered at NOAEL dose of 2000 mg/kg body weight per day and were gavaged once daily for 90 days. The rats were immunized with 0.1 ml Ranikhet disease vaccine R₂B strain intraperitoneally twice, once at 0 day post treatment and the second dose was given after one month. Humoral and Cell mediated immune responses were studied from 5 rats from both the groups at 30^th, 60^th and 90^th days post treatment. Results of immunological studies revealed mild to moderate variation in humoral and cell mediated immunity in group II rats as compared to group I rats. Within group II rats, at different time intervals, no significant variation was observed in any immunological parameter. It is concluded from the present study that administration of nanosilica at NOAEL dose of 2000 mg/kg body weight per day for 90 days have a decrease in HI titre and B lymphocyte blastogenesis assay by 2.3% and 3.24%, respectively. ELISA recorded 35.0% higher titre in 90 days post treatment in Wistar rats. In cell mediated immunity, the alterations were 18.0% and 6.37% in Con A and PHA-M stimulated splenic cells, respectively. However, the results were not statistically significant at 5% level of significance.