IMMUNOLOGICAL CHANGES AMONG WORKERS OCCUPATIONALLY EXPOSED TO STYRENE

The functional status of the immune system was investigated in a group of 71 workers exposed to styrene and in 65 control subjects, recruite d according to the same selection criteria and comparable as to sex, a ge, and confounding variables. Air and biological monitoring were used to characterize styrene exposure (median of the main urinary metaboli tes in the ''next-morning'' spot samples: 106 mg/g creatinine). Phenot ypic analysis of peripheral blood lymphocytes (PBL) by automated flow cytometry revealed a reduced proportion of T lymphocyte subsets (CD3(), CD4(+) and CD4(+) 45(+)), with no changes in CD8(+), and a higher p roportion of B lymphocytes (CD19(+)) among styrene-exposed workers. Th e exposed workers showed a higher proportion of activation markers, na mely DR and interleukin-2 receptors (CD25). Immunoglobulin subclasses were comparable in the two groups. An increased prevalence of abnormal ly low values apparent for CD2(+), CD3(+), CD4(+), CD4(+) 45(+) CD11b subsets among workers exposed to styrene, whereas CD19(+), DR(+) and C D25(+) showed an increased prevalence of abnormally high values. Natur al killer-related phenotypes (CD56(+), CD56(+) 16(+), and CD56(+) 16(- )) were more expressed among styrene workers, with average increase of 30%. However, the frequency distribution of the lytic activity of nat ural killer cells against K-562 target cells was shifted towards lower values in the exposed workers as compared to control subjects. Dose-r esponse relationships between indices of internal dose and prevalence of abnormal values were detectable for T lymphocyte subsets, NK phenot ypes, and activation markers. These findings suggest that moderate exp osure to styrene is associated with an altered distribution of lymphoc yte subsets. The decreased proportion of T lymphocytes, mainly of T he lper-inducer cells, could hamper regulatory functions, thus suggesting a negative modulation by styrene exposure. Since a proper balance bet ween immunocycte subsets is important for immunological responses, suc h changes should be regarded as adverse effects.