The aim of the study was to evaluate whether peripheral cellular parameters could predict susceptibility to decreased lung function and associated symptoms, in response to a single exposure to cotton dust. Previously nonexposed subjects (n = 42) inhaled an aerosol of cotton dust in a model cardroom during a period of 5 h. The subjects were examined before the exposure for FEV1, procoagulant activity (PCA) in blood mononuclear cells (BMNC), and serum IgE antibodies against a pool of inhalant antigens. Blood lymphocytes were typed into the helper/inducer (CD4+) and cytotoxic/suppressor (CD8+) T cells in combination with surface markers subdividing these populations. A questionnaire was used to identify atopic and nonatopic subjects. Immediately after exposure, the subjects were tested for FEV1 and PCA, and symptoms were recorded with a questionnaire. The dust exposure induced a decrease in FEV1 that was larger for the atopic group, but did not change the PCA in BMNC. The decrease in FEV1 was positively related to the preexposure PCA in both atopics and nonatopics. Symptoms from the airways after the exposure were reported to the same extent in the atopic and nonatopic group, and the subject group reporting chest tightness had a larger preexposure PCA. The atopic group had a larger proportion of blood CD8+ T lymphocytes negative for the monoclonal antibody anti-S6F1 (CD8+S6F1-), and in this group the decrease in FEV1 was significantly related to the proportion of this cell type. Also, in the atopic group, the proportion of CD8+S6F1- cells correlated positively with the preexposure PCA, and a negative correlation was found for this cell and serum levels of IgE.(ABSTRACT TRUNCATED AT 250 WORDS)