We investigated the effects of interleukin-3 (IL-3) on histamine relea
se (direct releasing and indirect enhancing effects) from basophils in
allergic asthmatic subjects. Interleukin-3 caused direct histamine re
lease (HR) in selected donors (IL-3 responders) and enhanced anti-IgE-
induced HR in other IL-3 nonresponders, although both direct releasing
and indirect enhancing activities of IL-3 on HR did not coexist with
each other. There was a significant correlation between IL-3-induced H
R and spontaneous histamine release (r = .8532, P < .0001).