IGG(4) BLOCKING EFFECT ON THE RELEASE OF ANTIGEN-SPECIFIC HISTAMINE

We evaluated the biological effect of IgG4 antibodies in pollinosis. W e studied the ability of IgG4 to mediate histamine release by measurin g anti-IgG4 in pollinic patients without previous immunotherapy. We al so evaluated the modifications that sera rich in specific IgG4 and IgG itself exert upon antigen-specific histamine release. According to ou r results, stimulation with anti-IgG4 did not induce histamine release , as opposed to stimulation with anti-IgE, which induced histamine rel ease in all the cases studied. On the other hand, hyperimmune sera fro m pollinic subjects under immunotherapy and with high levels of specif ic IgG4 significantly inhibited the release of antigen-specific histam ine from basophils of untreated patients. After isolating IgG4 by mean s of affinity chromatography, preincubation of this fraction with the allergen gave rise to a significant reduction in histamine release com pared to preincubation of the antigen with normal sera.