IgE containing immune complexes in serum and synovial fluid from patients with rheumatoid arthritis

Circulating immune complexes in patients with rheumatoid arthritis (RA) are composed of the immunoglobulins M and G, less frequent also A and E, and complement components. For determination IgE containing complexes (IK-E) are precipitated by polyethylene glycol 6,000, 2,5% in PBS. After extensive washing, the precipitate is solubilised in PBS and the IgE content measured by enzyme immunoassay. IK-E have been found in 3 sera out of 92 healthy donors (3%), in 43 out of 101 patients suffering from RA (43%), in 36 out of 83 patient with atopic dermatitis (43%), and 4 out of 50 patients with psoriasis vulgaris (8%). In 20 synovial fluids from RA patients, IK-E have been measured, too. The results obtained in sera and in synovial fluids are correlating. Patients, suffering less than 20 years from RA and having IK-E in serum, show a significantly higher restriction of mobility, measured by the mobility function test by Keitel, than patients without such complexes. After longer duration of the disease, these differences seem to disappear. For a precise statement, the number of patients suffering from RA longer than 20 years is to small. Circulating immune complexes have been measured too (Clq-binding test, not determining any immune globulin class). There was no difference between groups of patients with and without such complexes. Therefore, IK-E can be used as markers of a more severe disease. It can be assumed, that such complexes activate, or increase activation of cells expressing high-affinity IEE receptors, such as mast cells, and low affinity receptors (CD23), such as macrophages. Thus, the inflammation could be increased by IK-E.