In a 21-year-old female with severe atopic dermatitis, the secretion of interleukin-2 (IL-2), interleukin-4 (IL-4), and interferon-gamma (IFN-gamma) by her peripheral blood mononuclear cells (PBMC) was measured after incubation with/without antigens extracted from Dermatophagoides pteronyssinus (Dp), to which the patient had developed a positive patch-test reaction. Incubation with Dp antigen produced marked secretion of IL-2 and IFN-gamma, but not IL-4. This may suggest that Dp-specific T lymphocytes present in the circulating blood cells are capable of producing IL-2 and IFN-gamma, which may be relevant to the delayed-type allergic reaction occurring in the skin lesion.