Abstract
Adenosine deaminase (ADA) is an enzyme involved in purine metabolism and has a major role in the development and function of lymphoid cells. Congenital de” ciency of ADA results in severe immunode”ciency. Patients with congenital ADA de” ciency treated with polyethylene glycolconjugated bovine ADA develop antibodies to ADA. This leads us to investigate the role of antiADA antibodies in patients with systemic rheumatic diseases. Commercially available ADA was used in ELISA and immunoblots for detection of anti-ADA antibodies. Four out of 100 patients examined were positive for anti-ADA antibodies. Two of them had peripheral blood lymphopenia but the antibody levels did not appear to correlate with the lymphocyte counts. Immunoblotting revealed that the antibodies recognized a 40 kDa peptide of ADA, corresponding to ADA1, the major component of ADA. Af” nity-puri”ed antibodies were used to locate the distribution of ADA on Hep-2 cells and lymphocytes by indirect immuno‘ uorescence. Anti-ADA antibodies gave a distinct nuclear speckled pattern on acetone-”xed cells. With viable cell immuno‘ uorescence, antiADA antibodies also stained the cell surface of HEp-2 cells and lymphocytes, indicating surface expression of ADA. The anti-ADA antibodies failed to gain access into the cytoplasm or nuclei when added to the cultures of HEp-2 cells. In summary, this is the ” rst report of detection of antiADA1 autoantibody which is a new type of ANA with discrete, speckled nuclear staining, but which may not be associated with lymphopenia.
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