Patients sensitive to bee stings had immediate weal-and-flare (WF) and painful late reactions when skin tested with purified melittin, the main toxin of bee venom. The WF reactions were immunologically non-specific, as melittin is a potent histamine-releasing agent. The late reactions which persisted after 4–5 hr appeared to result from immunological hypersensitivity to bee stings since normal patients had no late reactions. Reaginic and precipitable antibodies against melittin were not found in the sera from any of the bee sting sensitive patients. Cellular hypersensitivity against melittin was not detected by the leucocyte migration inhibition test.
The haemolytic and leucocyte migration inhibition activities of melittin were associated with the intact molecule and not the carboxy-terminal heptapeptide.