Cloning and expression of a novel human antibody-antigen pair associated with Felty's syndrome

An increasing number of studies suggest the importance of antibodies in the pathogenesis of most systemic and organ-specific autoimmune diseases, alth ough there is considerable controversy over the precise role of the autoant ibodies involved. In humans, a major obstacle to progress is the identifica tion and cloning of the relevant autoantibodies and autoantigens. Here, an approach based on the sequential use of antibody phage display and antigen expression libraries is developed and applied to a donor suffering from rhe umatoid arthritis (RA), splenomegaly, and peripheral destruction of neutrop hils leading to neutropenia (Felty's syndrome). An antibody phage display l ibrary was constructed from bone marrow from the donor and a high-affinity human mAb, ANA15, selected by panning against fresh neutrophils and indepen dently by panning against a fixed cell line. The antibody showed strong sta ining of neutrophils and a number of cell lines. Probing of a lambda gt11 e xpression library from an induced myelomonocytic cell line with the mAb ANA 15 identified the eukaryotic elongation factor 1A-1 (eEF1A-1) as a novel au toantigen, The specificity of ANA15 was confirmed by reactivity with both p urified and recombinant eEF1A-1, Screening of a large panel of sera reveale d that 66% of patients with Felty's syndrome had elevated levels of anti-eE F1A-1 antibodies. The cloning of this antibody-antigen pair should permit r ational evaluation of any pathogenicity resulting from the interaction and its significance in neutropenia.