Background Low levels of autoantibodies (AAb) are in fact a normal feature of a healthy immune response. The distinction between pathological and natural AAb is not well understand.

Objectives To study the levels AAb specifically reacting with angiotensin-converting enzyme (ACE) and endogenous vasoactive mediators in sera patients with rheumatoid arthritis (RA) and healthy control group.

Methods We tested sera from 19 patients with RA, 12 pts had extra-articular manifestations, 7 pts had only joint damage. The patients were compared with 10 healthy donors. Solid- phase enzyme immunoassay was used to examine the levels of IgM AAb to ACE prepared from human kidney tissue and AAb to low-molecular peptides – bradykinin (BK), angiotensin II (AII) and vasopressin (VP).

Results Analysis of IgM AAb to vasoactive peptides showed a significant increase account AAb to bradykinin (BK) in sera from RA patients compared to donors (p = 0,0074). The highest value of AAb to BK were observed in RA patients without extra- articular features. Level of AAb to BK correlated with CIC, joint score (p < 0,05). Significant discrepancies between levels AAb to AII and VP in RA pts and donors have not been revealed. Level of AAb to AII correlated negative with ERS (r = -0,464, p < 0,05). Amount AAb to ACE was increasing in RA patients, but the differences were not significant.

Conclusion The biological effects of AAb to vasoactive peptides and ACE are unknown. The possible role of AAb to BK in the pathophysiology of joint inflammation requires careful consideration.