Several studies have suggested that activated T-lymphocytes and its derived cytokines are involved in asthma pathogenesis. To investigate the role of activated T-lymphocytes and interleukin-4 (IL-4) in asthma pathogenesis, we measured soluble interleukin-2 receptor (sIL-2R) and IgE concentrations in serum and production of IL-4 in situumlated peripheral blood mononuclear cell cultures from asthmatics by means of ELISA. The results showed: (1) sIL-2R (512.82 x 10(3) +/- 264.62 x 10(3) U/L) and IL-4 (1,842.42 +/- 824.60 ng/L) levels in acute severe asthmatics were significantly higher than those of controls (242.32 x 10(3) +/- 108.64 x 10(3) U/L and 406.32 +/- 62.16 ng/L, P < 0.01); (2) there was a positive relationship between IL-4 and serum total IgE (r = 0.492); there was a significantly negative relationship between IL-4 and FEV1% (r = -0.821, P < 0.05); (3) after intravenous administration of dexamethasone (DXM) 5 mg daily for 5 days, sIL-2R and IL-4 decreased respectively to (332.61 x 10(3) +/- 124.62 x 10(3) U/L and 314.10 +/- 72.08 ng/L, P < 0.05). These data indicate that activated T-lymphocytes and its derived IL-4 play an important role in asthma pathogenesis and that the effect of steroid on the treatment of asthma is partly due to inhibition of activated T-lymphocytes and IL-4 release.