Impaired in-vitro lymphocyte responses in patients with elevated pentachlorophenol (PCP) blood levels.

Immune parameters were examined in 188 patients who were exposed for more than 6 mo to pentachlorophenol-containing pesticides. Blood levels of pentachlorophenol, lymphocyte subpopulations, in-vitro responses to mitogenic and allogeneic stimulation, plasma neopterin levels, and plasma cytokine and cytokine receptor levels were determined. Impaired in-vitro lymphocyte stimulation responses were impaired in 65% of the patients. The likelihood of impaired lymphocyte stimulation increased significantly with levels of pentachlorophenol that exceeded 10 microliters/l (p < .05). Patients who had high blood levels of pentachlorophenol and abnormal lymphocyte stimulation also had increased proportions of blood monocytes in blood (p < .05), as well as increased IL-8 serum levels (p < .02). Eleven patients who had abnormal mitogen stimulation experienced decreased CD4/CD8 ratios of < 1.0; 5 of these patients had decreased CD4+ lymphocyte counts of < 500/microliters, and 3 patients had increased plasma neopterin of > 15 nmol/l. These results indicate that increased levels of pentachlorophenol in blood can lead to severe T lymphocyte dysfunction.