Evaluation of chemical-mediated alterations in production of cytokines derived <i>in vitro</i> from THP-1 cell line

Immune responses occur through orchestration of various immune components. Considering immune system complexity, immunotoxicity was evaluated primarily <i>in vivo</i> in rodents. Worldwide restrictions in animal use for toxicity research has driven development of <i>in vitro</i> methods for screening chemicals postulated to be potentially immunotoxic. One <i>in vitro</i> assay of immunotoxicity (IMMUNOTOX-T) uses human monocytic leukemia cell line THP-1. Since cytokine profiling might predict immunotoxicities, the aim of this study was to determine levels of 27 cytokines derived from THP-1 cells in response to chemical treatment. Seven immunosuppressives and 14 non-immunotoxicants <i>in vivo</i> were used as references to distinguish between immunosuppression and aberrant immunostimulation. Immunotoxicity of 41 <i>in vivo</i> immunomodulatory chemicals, at 0.01×, 0.1×, or 0.5× of 75% cell viability concentrations, was tested under blinded conditions by measuring relative cytokine production level (RCPL, %) versus control. The mean cytokine production value for immunosuppressants (MCPVS) of each cytokine was calculated by averaging mean RCPLs of three test concentrations of seven immunosuppressants. The acceptable cytokine production range (ACPR) for 14 non-immunotoxicants was defined as the highest mean RCPL of these 14 non-immunotoxicants for each cytokine. A target test substance was considered immunotoxic if mean RCPL of three test concentrations of the substance for at least one cytokine was below MCPVS or above the highest ACPR. Of 41 substances tested, 40, all except toluene, exhibited immunotoxic properties, with 9 and 6 substances downregulating and upregulating immune activity, respectively. This assay may contribute to the identification of immunotoxicological properties attributed to exposure to chemical substances.