In vitro studies on immunotoxic potential of Orange II in splenocytes

Orange II, an azo dye, is not permitted in food preparations, but high levels of the dye have been detected in different food commodities. Though there are reports on the toxicity of Orange II but knowledge based on the immunomodulatory properties of Orange II is scanty. The present investigation was undertaken to study the in vitro immunotoxic potential of Orange II in splenocytes. Splenocytes were isolated, cultured and subjected to immunophenotypic analysis, mixed lymphocyte reaction (MLR) assay or stimulated with lipopolysaccharide (LPS) or concanavalin A (Con A) for 72 h. The supernatant was collected for cytokine assays. Orange II showed cytotoxic effects at 100–1000 μg/ml concentrations and 50 μg/ml was determined as the highest non-cytotoxic dose. Orange II at the non-cytotoxic dose (50 μg/ml) significantly altered the relative distribution of T and B-cells, MLR response and the mitogen induced proliferative response of T-cells and B-cells. Consistent with the hypo-responsiveness of the T and B-lymphocytes, Orange II induced a concomitant decline in the secretion of cytokines IL-2, IL-4, IL-6, IFN-γ, TNF-α and IL-17. On the contrary, there was an increase in the production of IL-10, an anti-inflammatory regulatory cytokine, which may be one of the causative factor for immunosuppressive property of Orange II. These results suggest that non-cytotoxic dose of Orange II may have immunomodulatory effects.

► Orange II, an azo dye, found in different food stuffs, induces immune suppression.
► Orange II alters the relative proportions of T and B cells in splenocytes.
► Orange II causes lymphocyte hypo-responsiveness on stimulation with Con A or LPS.
► Orange II shows suppressive effect on the Con A or LPS stimulated release of cytokines.
► The decrease in mitogen induced cytokines by Orange II suggests its immunotoxicity.