The lesions of urticarial vasculitis tend to be flatter erythematous patches that hurt rather than itch and last longer than the more typical itchy wheals. Chronic inflammatory infiltrates are found around venules with deposits of immunoglobulins and complement. CICs may adhere to endothelium and trigger inflammation in blood vessel walls. In Bechet's disease, an occlusive vasculitis, the basement membrane of the vessel is under attack resulting in small vessel infarction with perivascular infiltration of lymphocytes. CICs and Complement Complement is a series of serum proteins that undergo progressive transformation into active by-products, once activated.
Classical pathway is triggered by antibody in immune complexes or attached to cell walls.
The complement system modulates and amplifies the biological effects of CIC's. At the same time, certain complement products are essential to clear CICs. Individuals with deficiencies of complement proteins C1, C2 and C4 are at greater risk of developing immune-complex disease. C3 deficient individuals suffer from recurrent infections rather than immune complex disease. CIC's may not cause tissue injury unless vascular permeability is increased - allowing influx of CIC's and cells.