MOLECULAR CHARACTERISTICS OF ANTI-SELF ANTIBODY FRAGMENTS AGAINST NEUTROPHIL CYTOPLASMIC ANTIGENS FROM HUMAN V-GENE PHAGE DISPLAY LIBRARIES

Recently it has been demonstrated that human antibody fragments with b inding activities against self antigens can be isolated from repertoir es of rearranged V genes from non-immunized humans. We have applied ph age display technology to study the B cell repertoire for antibody act ivity against neutrophil cytoplasmic antigens. These antibodies may pl ay an important role in Wegener's granulomatosis (WG) and related form s of vasculitides. Autoantibodies in patients with WG are directed aga inst proteinase 3. The immunodominant antigen in other forms of vascul itis is myeloperoxidase, but the B cell response can also be directed against other neutrophil enzymes, e.g. lysozyme, human neutrophil elas tase, lactoferrin and cathepsin G. We show here that anti-self reactiv ity against neutrophil cytoplasmic antigens can be detected in the rea rranged V gene repertoire of healthy individuals and that the reactivi ty can be directed against structural related epitopes which are prese nt on different neutrophil cytoplasmic antigens. The scFv with binding activities were sequenced and the V gene usage, the level of somatic mutations and the immunoserological characteristics of the antibody fr agments are discussed. Further evidence is presented that antibody fra gments consisting only of a heavy chain variable domain can recognize neutrophil cytoplasmic antigens in a specific manner. These single-dom ain antibody fragments were used in experiments designed to establish the relative role of the light chain variable domains in antigen bindi ng.