Demonstration of idiotypes expressed on basophil-bound IgE antibodies by using anti-idiotype-induced histamine release in grass pollen-allergic patients.

This study was designed to analyse further the idiotypic cross-reactivity between anti-Lol p I murine monoclonal antibodies of IgG isotype and basophil-bound human IgE antibodies from grass pollen-sensitive patients. It was also designed to determine the expression frequency of the idiotypes present on cell-bound IgE. Rabbit anti-idiotypic antisera were produced against idiotypes of three anti-Lol p I monoclonal antibodies (290A-167, 539A-6 and 348A-6) of different specificities. Basophils from 19 patients reacting to Lol p I allergen, as shown by positive skin test reactions and by the presence of serum-specific IgE antibodies (measured by RAST), were challenged with these rabbit anti-idiotypic antibodies and the histamine released was measured. Our data indicate that IgE-borne idiotypes were expressed as follows: (i) co-expression of the three idiotypes in 15% of patients; (ii) co-expression of two idiotypes in 21% of patients; and (iii) expression of a unique idiotype (290A-167) in 42% of patients. Among the three idiotypes, 290A-167 was shown to be a public idiotype since it was expressed in 80% of patients. Fab fragments of anti-idiotypic antibodies could inhibit anti-idiotype-induced histamine release, but optimal conditions varied from one patient to another.