IMMUNE CELL FUNCTIONS IN INDUSTRIAL-WORKERS AFTER EXPOSURE TO 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN - DISSOCIATION OF ANTIGEN-SPECIFIC T-CELLRESPONSES IN CULTURES OF DILUTED WHOLE-BLOOD AND OF ISOLATED PERIPHERAL-BLOOD MONONUCLEAR-CELLS

A comparative analysis was performed of the phenotype and function of peripheral blood leukocytes of two age-matched cohorts of industrial w orkers in chemical plants, one of which was exposed occupationally to high concentrations of 2,3.7,8-tetrachlorodibenzo-p-dioxin (TCDD). Med ian actual TCDD burdens were 116 ng/kg and 4 ng/kg, respectively. The phenotype analysis oi peripheral blood mononuclear cells (PBMC) reveal ed no significant differences in the proportions of CD3, CD4, or CD8() T lymphocytes, of CD16(+) natural killer cells, and of CD19(+) B lym phocytes. However, in PBMC of the TCDD-exposed workers, the proportion of CD8(+) memory T cells (CD45RO(+)) was significantly higher, and th at of lymphocytes with naive phenotype (CD45RA(+)) was significantly l ower than in PBMC of the control group. Polyclonal and antigen-specifi c T-cell activation was assessed in parallel in isolated PBMC as well as in diluted whole blood cultures. in both culture systems the polycl onally stimulated cytokine release did not differ significantly betwee n the two cohorts, however, we found a significantly reduced interfero n gamma release in diluted whole blood cultures but not in isolated PB MC cultures of the TCDD-exposed cohort when we performed an antigen-sp ecific T-cell stimulation with tetanus-toroid. Therefore, we propose t hat exposure of individuals to high doses of TCDD can partially impair in the ''blood milieu'' those T-cell/monocyte interactions that are e ssential for antigen-specific T-cell responses, whereas isolated PBMC of the same donors appear functionally less affected.