Immunologic responses during allergen-specific immunotherapy for respiratory allergy.

At present there is no absolute way to determine which patient will respond to immunotherapy and which will not. Even in treated patients who derive clinical benefit, there is no one "best" immunologic parameter to follow although the generation of allergen-specific IgG seems to correlate better with clinical improvement than the other parameters. Whether or not the measurement of allergen-specific IgG4 will prove to be a useful clinical parameter is still a controversial issue and is an area for active investigation. The reason that IgG4 becomes elevated selectively over time during immunotherapy is not clear nor is its function known in the immune response to allergen. It is of interest however that IgG4 does not fix complement and may therefore account for the absence of immune complex disease in patients treated over many years. The modification of allergens through denaturization so that they are less reactive with preformed IgG has resulted in potent preparations that induce a strong IgG response. These preparations permit flexibility in dosage and in frequency of administration as well as produce no greater side effects than aqueous extracts. While these preparations would be a decided advantage over existing extracts, recent information that is accumulating regarding T cell recognition of antigen opens the way for more precise targeting of our therapy. That is, determination of the antigenic epitopes that trigger helper T cells should permit the construction of peptides that can "block" T cell recognition and potentially lead to immunologic unresponsiveness.(ABSTRACT TRUNCATED AT 250 WORDS)