BACKGROUND: Type I allergy to latex is a growing problem, especially among health care workers. A detailed study of the peripheral blood cell responses to latex allergens has not been reported. METHODS: Peripheral blood mononuclear cells of patients and healthy subjects were isolated and stimulated with protein extracts from latex sap and latex gloves and the purified latex allergen Hev b 1 (rubber elongation factor) at different concentrations to determine the antigen-specific proliferation response. The examined patients were sensitized to latex by occupational exposure (n = 23) and had rhinitis, conjunctivitis, contact urticaria, and/or asthma. Two control groups of nonsensitized subjects were studied: one occupationally exposed to latex (n = 8), and the second, not exposed to latex (n = 8). RESULTS: In general, only latex-exposed subjects responded to the different latex antigen preparations. Lymphocyte proliferation responses to latex sap extract were found in 65% of latex-sensitized subjects and in 37.5% of the latex-exposed healthy subjects. Latex glove extract induced a significant proliferative response in 47.8% of latex-sensitized patients and in 25% of latex-exposed individuals. Hev b 1 induced lymphocyte proliferation responses in 52% of the latex-sensitized patients and in 25% of the latex-exposed subjects, indicating that Hev b 1 is relevant antigen in these latex-sensitized and latex-exposed groups. Peripheral blood mononuclear cells of 39.1% of the latex-sensitized subjects responded to all three allergen preparations (latex sap and latex glove extract, as well as Hev b 1). We could find no correlation between latex-specific IgE level and latex-induced lymphocyte proliferation response. CONCLUSION: Our data indicate that the 14 kd protein Hev b 1 is a relevant allergen in health care workers. It can be detected by specific IgE antibodies to Hev b 1, as well as in lymphocyte proliferation assay. In addition, our study suggests that antigen-specific proliferation response to latex is associated with exposure to latex, but not with the level of specific latex IgE. This may be useful for the evaluation and prediction of latex hypersensitivity development. (J ALLERGY CLIN IMMUNOL 1996;98:640-51.)