Altered distribution of lymphocyte subpopulations and augmentation of lymphocyte proliferation in chronic PCB...

To clarify the mechanism of immunotoxicity of polychlorinated biphenyls (PCB), delayed type hypersensitivity skin test, lymphoproliferative responses, and lymphocyte subpopulations defined by monoclonal antibodies were performed on 30 patients and 38 age/sex-matched healthy individuals. Three years ago the patients had ingested rice bran oil accidentally contaminated by PCB. Except for lymphocyte proliferation, the chronic effect of PCB and its derivatives upon cell-mediated immunity (CMI) in these patients was not so evident when compared to that found within one year of exposure. Delayed type hypersensitivity skin response to purified protein derivative (PPD) and the numbers of peripheral T and B lymphocytes were within normal range. The enumeration of lymphocyte subsets demonstrated decreased T4 (inducer/helper) cells and increased T8 (cytotoxic/suppressor) cells. The abnormally augmentated spontaneous proliferation and proliferation responses to phytohemagglutinin (PHA), concanavalin A (Con A), pokeweed mitogen (PWM) and PPD implicated that both T and B lymphocytes were functionally affected. This may well be the result of the immunotoxicity rather than the enhancement of cell-mediated immunity by these toxic compounds. While there was no correlation between the results of those assays and blood PCB levels, it appears that the lymphoproliferative assay may be applied as a sensitive test in reflecting the severity of PCB immunotoxicity.