Immunological effects of occupational exposure to metallic mercury in the population of T-cells and NK-cells†

Abstract

This paper presents a study of the counts of lymphocytes, (CD3+)T-cells, (CD4+)T-helper and (CD8+)T-suppressor and (CD16+)NK-cells in the peripheral blood of 101 males with a history of occupational exposure to metallic mercury vapours (Hg⁰) and in 36 males without this exposure. These workers were divided depending on the duration of exposure: 37 males with a short-term history of exposure to Hg⁰ (up to 10 years) and 64 males with a history of long-term exposure (10 to 37 years). For the determination of T-cell populations monoclonal antibodies were used in indirect immunofluorescence tests. The time weighted average of mercury concentrations in air was 0.028 mg m^–3. Mercury concentration in the urine of the exposed subjects ranged from 20–260 µg dm^–3, and in blood it was from 4 to 72 µg dm^–3. Stimulation of the T-cell line was noted as evidenced by increased numbers of (CD3+)T-cells, (CD4+)T-helper and (CD8+)T-suppressor cells in the workers with <10 or >10 years’ exposure to Hg⁰. Lower increase count of (CD3+)T-cells and (CD4+)T-helper cells than (CD8+)T-suppressor cells was the cause of decreased values in the (CD3+)T/(CD8+)T-suppressor ratio and (CD4+)T-helper/(CD8+)T-suppressor ratio in the workers with <10 or >10 years’ of exposure. Moreover, no changes were observed in the T-cell populations between workers with <10 and those with >10 years’ exposure. In addition, statistical analysis of the effects of age and duration of exposure to Hg⁰ on the studied immunological parameters indicates that exposure duration may affect some of the values. These quantitative changes of T-cell population as well as changes of the (CD3+)T/(CD8+)T-suppressor and (CD4+)T-helper/ (CD8+)T-suppressor ratio have been proposed as immunological indicators of exposure to Hg⁰, which can be used for monitoring and to explain the origin of autoimmunity disorders induced by metallic mercury.