Answer: reagin

AnswerCrossword Clue
reagina type of antibody (a body substance that produces immunity against toxins)
reagina substance in the blood of persons with syphilis responsible for positive serological reactions for syphilis
reaginantibody formed in response to syphilis and reactive with cardiolipin in various blood tests for the disease
reaginantibody (as IgE in humans) that mediates hypersensitive allergic reactions of rapid onset
reaginantibody found in certain human allergies, as hay fever and asthma