REGULATION AND TARGETING OF T-CELL IMMUNE-RESPONSES BY IGE AND IGG ANTIBODIES

A set of chimeric antibodies with identical F(ab')(2) fragments specif ic for the hapten 5-iodo-4-hydroxyl-3-nitrophenacetyl (NIP), but with different human Fc parts (gamma 1, gamma 2, gamma 3, gamma 4, epsilon) , was used to compare the role of IgG and IgE antibodies in antigen pr esentation by human Epstein-Barr virus (EBV) B cells. Two or three mol ecules of NIP were coupled to one molecule of Der pI (Der pI-(3)NIP), a major allergen of Dermatophagoides pteronyssinus. Both monomeric IgG and preformed complexes of various Der pI/IgG ratios failed to bind s ignificantly to the Fc receptor for IgG on B cells (Fc gamma RII; CD32 ). Binding of IgG3 (>lgG1)-containing complexes (optimal ratio of anti gen to antibody = 1 : 1) could be enhanced by increasing the number of haptens per Der pI molecule to nine or more. However, antigen present ation mediated by IgG and CD32 was not seen with either pulsed B cells or B cells that were allowed to capture the IgG complexes during the whole stimulation period. IgE binding to CD23 and subsequent IgE-media ted antigen presentation was seen under all conditions tested. Even mo nomeric immune complexes (IC) (Del pI-(3)NIP/IgE), in the absence of C D23 cross-linking, induced an immune response. As the number of natura l epitopes for human antibodies on Der pI was less than five, we concl ude that, in vivo, complexes consisting of Der pI/IgG will be directed to antigen-presenting cells expressing the high-affinity receptor for IgG (CD64), whereas IgE will allow antigen presentation by CD23-expre ssing cells, including B cells.