Naïve (CD4+CD45RA+) T cell subpopulation is susceptible to various types of hazardous substances in the workplace.

To find the most susceptible lymphocyte subpopulation with exposure to various occupational hazardous substances, we reanalyzed our previous data. We measured T, B and natural killer NK cell subpopulations by means of flowcytometry among workers who were exposed to aromatic amines, chromate, mercury lead and organic-solvents. The exposed/non-exposed ratio was defined as the mean value of the absolute number of lymphocyte subpopulations in the exposed workers divided by the corresponding value of the non-exposed control group in 5 studies reported previously by us. The ratio of CD4+CD45RA+ T cells in all the exposed groups examined in this study was less than 1.0, and the mean of these ratio was 0.77, which was the lowest among lymphocyte subpopulations examined. The mean ratio was 1.06 for CD4+CD29+ T cells, 0.91 for CD4+ T cells, 0.99 for CD8+ T cells, 0.93 for CD3+ T cells, 0.99 for CD19+B cells, 0.96 for CD57-CD16+ NK cells, 0.82 for CD57+CD16+ NK cells, 1.25 for CD57+CD16- NK cells and 0.89 for total lymphocytes. With regard to the difference between exposed and non-exposed workers the estimated overall difference in the mean absolute number of CD4+CD45RA+ T cell subpopulation between exposed and non-exposed workers among five studies was -135 ((% confidence interval, CI: (-194,-75)) cells/mm3 (p<0.01). In conclusion, naïve (CD4+CD45RA+) T cell subpopulation was the most susceptible to the effects of various toxic substances as compared with other lymphocyte subpopulations. This lympohocyte subpopulation may be useful for monitoring immune system of workers exposed to various types of substances in the workplace.