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Clinical and Diagnostic Laboratory Immunology, November 2002, p. 1253-1259, Vol. 9, No. 6
1071-412X/02/$04.00+0 DOI: 10.1128/CDLI.9.6.1253-1259.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.
Rheumatology Section,1 Cardiovascular Center, Department of Medicine, University of Chile Clinical Hospital, Santiago, Chile,2 Department of Pathology, Duke University Medical Center, Durham, North Carolina 277103
Received 4 October 2001/ Returned for modification 29 January 2002/ Accepted 17 July 2002
Dipeptidyl peptidase IV (DPP IV) (CD26) plays a critical role in the modulation and expression of autoimmune and inflammatory diseases. We recently reported that sera from patients with rheumatoid arthritis and systemic lupus erythematosus contained low levels of DPP IV and high titers of anti-DPP IV autoantibodies of the immunoglobulin A (IgA) and IgG classes and found a correlation between the low circulating levels of DPP IV and the high titers of anti-DPP IV autoantibodies of the IgA class. Since streptokinase (SK) is a potent immunogen and binds to DPP IV, we speculated that patients with autoimmune diseases showed higher DPP IV autoantibody levels than healthy controls as a consequence of an abnormal immune stimulation triggered by SK released during streptococcal infections. We assessed this hypothesis in a group of patients suffering from acute myocardial infarction, without a chronic autoimmune disease, who received SK as part of therapeutic thrombolysis. Concomitant with the appearance of anti-SK antibodies, these patients developed anti-DPP IV autoantibodies. These autoantibodies bind to DPP IV in the region which is also recognized by SK, suggesting that an SK-induced immune response is responsible for the appearance of DPP IV autoantibodies. Furthermore, we determined a correlation between high titers of DPP IV autoantibodies and an augmented clearance of the enzyme from the circulation. Serum levels of the inflammatory cytokines tumor necrosis factor alpha (TNF-
) and interleukin 6 (IL-6) increased significantly after 30 days of SK administration, while the levels of soluble IL-2 receptor remained unchanged during the same period, suggesting a correlation between the lower levels of circulating DPP IV and higher levels of TNF-
and IL-6 in serum in these patients.
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