SUMMARY
SUMMARYProtective immunity is provided by the interplay between the innate and the adaptive arms of the immune systems. The innate as well as the adaptive immune response is regulated by specialized cells with the challenging task to eliminate pathogens while not damaging the host itself. Usually the immune system copes well with this charge, but is not always successful. Furthermore, proinflammatory lipids, cytokines, and chemokines are produced and released, leading to an allergic inflammation. Although frequency of individuals suffering from allergies has increased exponentially over the last century, the only available therapy that stops disease progression is allergen-specific immunotherapy (SIT). Even though allergenspecific antibodies have been reported to play an important role in SIT, mechanisms of IgGmediated inhibition of allergic reactions are not well defined.The present studies aimed to provide better understanding of the mechanisms how allergenspecific IgG antibodies may modulate allergic responses. Therefore, we generated monoclonal antibodies (mAbs) that recognize three non-overlapping epitopes on the major cat allergen Feld1. Each of the three mAbs was produced as IgE or different IgG isotypes. We found that IgE antibodies against two non-overlapping epitopes on Feld1 were required and sufficient to sensitize mast cells for maximal activation upon exposure to monomeric Feld1.