Respiratory involvement and immune status in polychlorinated biphenyls and polychlorinated dibenzofurans poisoning

Respiratory distress and abnormalities of clinical and laboratory investigation of 401 patients with polychlorinated biphenyl (PCB) and polychlorinated dibenzofuran (PCDF) poisoning have been studied from 1969 to 1983. About half of the patients were complaining of respiratory distress and or secondary airway infections at an early stage. The repiratory distress occurring in these patients improved gradually for 10 years following onset of the disease. Over the next 5 years (from 10 to 15 years after onset) little or no improvement of respiratory symptoms was observed in most cases. Pathophysiological studies showed that respiratory involvement in Yusho was mainly that of small airways disease and the disease state was mildly improved in 1983. The effect of PCDF on 1) helper and suppressor T-cell subsets and 2) the response to nonspecific mitogen-PHA was studied in Japanese Yusho patients 14 years after onset. High OKT 4/8 ratio (helper/suppressor T-cell ratio) and lowered responsiveness to PHA were seen. Conversely, Yan-Chin Lu reported a low OKT 4/8 ratio and enhanced responsiveness to PHA in Chinese PCB poisoning patients 3 years after onset. In order to clarify these discrepancies, and to analyze the effects of PCDF on lung tissue and immune status, animal experiments were done. The results suggest that PCDF leads to severe toxicity to bronchiolar Clara cells and thymus, as compared with that of PCB. In addition helper T-cells are selectively damaged in the acute phase of the PCDF poisoning as shown in Chinese patients. Further, the results suggest that in PCDF poisoning the T-cell function is suppressed, while the function of neutrophils is activated. It is not clear, however, whether these changes are direct effects or indirect ones of PCDF, but it is suggested from our study that these abnormalities correlate with chronic bronchitis-like symptoms in Yusho patients.