Immunotoxicology in occupational and environmental health: Perspectives, restraints and aims of research

The immune system is able to recognize and neutralize potentially harmful agents, conferring to the organism resistance to infections and malignant diseases. The authors have reviewed the literature and identified a group of substances able to enhance and/or reduce different immune functions, both in an experimental model and in occupational and environmental human exposure. The group includes several polyhalogenated hydrocarbons, particularly polychlorinated biphenyls, polybrominated biphenyls, tetrachloro-dibenzo-p-dioxin (TCDD), some metals like lead, cadmium and mercury, pesticides, i.e. dithiocarbamates and organotin compounds, organic solvents. The observed changes are usually slight and do not allow prognostic conclusion. In this study, the authors propose a 3-level rank of tests suitable for the immune evaluation of individuals occupationally exposed to xenobiotics, divided into three levels, as follows: tier 1: immunoglobulin classes (IgG, IgA, IgM), complement fractions (C3, C4), rheumatoid factor, and non-organ specific autoantibodies (AMA, SMA, ANA); CD3, CD4, CD8, CD57, CD20, HLA-DR; CD3/HLA-DR positive lymphocyte subsets; tier 2: determination of the mitotic response of peripheral blood lymphocytes to phytohaemoagglutinin, anti-CD3 monoclonal antibody, phorbol-myristate- acetate (PMA) and polyclonal immunoglobulin production after stimulation with pokeweed mitogen; tier 3: cytokine production with and without mitogen stimulation. The approach is 'step by step' and assumes the need of a closely integrated and comparative evaluation of the findings obtained. The protocol could be used in research fields; moreover, some of the tests could be useful in the monitoring of persons exposed in the environment or in the workplace to immunotoxic substances or to biological agents.