['During or after surgery, asthma attacks due to airway hyperresponsiveness (AHR) are likely to occur in patients with bronchial asthma. Preoperative administration of corticosteroid for prevention of perioperative asthma attacks is useful. We examined the mechanism of prevention of perioperative asthma attacks by the preoperative administration of corticosteroid in vitro.', 'Five patients with asthma were treated with 20 mg of prednisolone orally for 2 preoperative days and 80 mg of methylprednisolone IV immediately before and after surgery. In another five patients without asthma, no steroids were administered. A noncarcinomatous part of the resected tissue from each patient with lung cancer was passively sensitized with the serum of an atopic patient. In the patients without asthma, the tissue was treated with or without dexamethasone, and then mite antigen was added.', 'The culture supernatant and lung tissue were recovered, and the supernatant was assayed for histamine, leukotriene E(4) (LTE(4)), interleukin (IL)-5, and tumor necrosis factor (TNF)-alpha. Degranulation of mast cells was measured by tryptase staining of the lung tissue, and the expression of messenger RNA (mRNA) of IL-5 and TNF-alpha was determined by the reverse transcriptase-polymerase chain reaction method.', 'While preoperative administration of corticosteroid did not suppress the release of histamine and LTE(4) from the lungs of asthmatic patients, it completely suppressed IL-5 and TNF-alpha production at the mRNA level. The same results were obtained in lung tissues of nonasthmatic patients treated in vitro with dexamethasone.'] Does preoperative steroid therapy inhibit cytokine production in the lung parenchyma in asthmatic patients?