Features of the autoantibody profile in women with systemic lupus erythematosus and endometriosis

Endometriosis is a chronic inflammatory disease of women, occurring primarily during reproductive age, with high incidence of various autoimmune diseases such as systemic lupus erythematosus (SLE). SLE is characterized by a variety of clinical manifestations and hyperproduction of various antinuclear antibodies. Their role in pathogenesis of endometriosis is actively discussed. We have collected clinical and laboratory data of 53 women (mean age 39.5±9.3 years) with chronic SLE who had gynecological reports on negative or positive assessment of endometriosis, in order to evaluate the patterns of autoantibody profile in women with SLE, dependent on the presence of endometriosis. We determined the following antibodies: antinuclear factor (ANF) by indirect immunofluorescence on HEp-2 cells; antibodies to double-stranded DNA (anti-dsDNA), antibodies to Smith antigen (anti-Sm-IgG), to cardiolipin (IgG/IgM), and to β2-glycoprotein-I (anti-β2GP-I) using appropriate immunoassay kits. The levels of anti-DNA and anti-Sm-IgG were higher in subjects with endometriosis, but the differences did not reach statistical significance (p = 0.068 and p = 0.079, respectively). Similarly, no intergroup differences were observed for antibodies to cardiolipin of different classes and anti-β2GP-I (p 0.1). A higher proportion of patients with positive ANF titers ( 1:160) was found in the group of SLE patients with endometriosis (p = 0.034), with antibody titer 1:320 found in 64.7% of these patients. All ANF-positive samples were diluted to a final titer of 1:1280 and characterized by the type of nuclear staining. The most frequent pattern was homogeneous (45.3%) and granular (41.5%), which combined fine-granular, coarse-granular, and dense fine-granular types of luminescence. Granular type of luminescence was more frequently detected in patients with endometriosis (11/17 vs. 11/36; χ2Yates, p = 0.04), reflecting the reaction of autoantibodies with nucleoprotein complexes. When several types of ANF luminescence were detected in the same sample, one of them (usually at low titers) interfered with others, and changed when the dilution titer was increased to 1:640 – 1:1280 (9 individuals with different transition variants). It seems that the characterization of ANF luminescence type may provide more valuable information in future management of SLE patients with comorbid pathology. Further studies are needed to evaluate the role of ANF in pathophysiologic mechanisms of endometriosis in SLE.