The role of alpha-tocopherol (alpha-toco) and selenium (Se) on human lymphocyte oxidative stress and T-cells proliferation were studied by flow cytometry. We measured the hydrogen peroxide and glutathione levels in cultured human T-lymphocytes and the proliferation of their subsets: T-helper/inducer, T-suppressor/cytotoxic, and natural killer and interleukin-2 receptors upon stimulation by the mitogens phytohemaglutinin (PHA) and lipopolysaccharide (LPS). The results indicate that early stimulation by mitogens is affected by the glutathione and hydrogen peroxide status of the T-lymphocytes. The addition of 100 microM or 500 microM alpha-toco or 0.5 microM Se alone shows weak antioxidant and immunostimulant properties. When combined, an enhanced antioxidant and immunoregulatory effect was observed. The present findings indicate that alpha-toco and Se have interactive effects as oxygen radical scavengers, thus promoting human lymphocyte response to antigens. This suggests that micronutrient status is an important factor in considering when interpreting the results of in vitro assays of lymphocyte function.