Objective: Endothelial cell growth factor (ECGF) was recently identified as the first autoantigen known to be a target of T cell and B cell responses in ~20% of patients with antibiotic-refractory Lyme arthritis. The goal of the current study was to look for a pathologic correlate between ECGF autoantibody responses and histologic findings in synovial tissue.
Methods: Synovial tissue was examined from 14 patients with antibiotic-refractory Lyme arthritis and 6 patients with other forms of chronic inflammatory arthritis, primarily rheumatoid arthritis. The tissue sections were subjected to chemical and immunostaining, and IgG antibody responses to ECGF were determined by enzyme-linked immunosorbent assay (ELISA). Each finding was ranked for statistical analysis.
Results: In each disease, synovial tissue showed synovial hypertrophy, vascular proliferation, immune cell infiltrates, and fibrosis. However, among the 14 patients with antibiotic-refractory arthritis, 8 (57%) had obliterative microvascular lesions in the tissue, compared with none of the 6 patients with other forms of chronic inflammatory arthritis (P = 0.04). Among the patients with Lyme arthritis, 5 (36%) had autoantibody responses to ECGF, and all 5 had obliterative lesions, as compared with only 3 of 9 patients who lacked ECGF antibody responses (P = 0.009). Moreover, the magnitude of ECGF antibody responses correlated directly with the extent of obliterative lesions (P = 0.02) and with greater vascularity in the tissue (P = 0.05).
Conclusion: The correlations of ECGF autoantibody reactivity with obliterative microvascular lesions imply that these autoantibodies may be involved in the obliterative process, suggesting that anti-ECGF antibodies have specific pathologic consequences in the synovial tissue of patients with antibiotic-refractory Lyme arthritis.
Copyright © 2014 by the American College of Rheumatology.