Children with asthma usually become asymptomatic by the time they reach age 20 y. To clarify the immunologic mechanisms responsible for this phenomenon, we studied patients in remission and others who still had frequent asthma attacks. Patients were grouped by clinical status, and three variables were measured: serum levels of lgE, production of 11.4 and interferon (IFN)-γ, and the activation of T cells induced byDermaophagoides farinae(DF) antigen. Df-induced activation of T cells (as measured by antigen-induced 11.2 responsiveness) or 11.2 synthesis itself was induced in patients with active asthma but not in normal subjects. These responses were much weaker in patients in remission. When stimulated by Df antigenin vitro, lymphocytes from patients with active asthma produced much more 11.4 than did the cells from normal subjects, and cells from patients in remission produced only a small amount. In contrast, under similar conditions lymphocytes from patients with active asthma produced less IFN-γ than did the cells from normal subjects. Production of IFN-γ stimulated by Df antigen was high in patients in remission but not in normal subjects. Thus, up-regulated IFN-γ production after exposure to Df antigen might reduce 11.4 secretion, which would suppress IgE production and would improve clinical status. Df antigen may suppress Df-induced allergic responses in patients with asthma in remission.