Serological testing for neutrophil granulocyte cytoplasmic antibodies (ANCA) is an important aid in the diagnosis of autoimmune diseases like Wegener's granulomatosis, rapid progressive glomerulonephritis, polyarteritis, ulcerative colitis, primary sclerosing cholangitis. ANCA are autoantibodies directed against antigens found in cytoplasmic granules of neutrophils and monocytes. ANCA are classified according to the immunfluorescence patterns they produce on normal neutrophils and according to their target antigens. At least two fluorescence patterns can be differentiated: a granular fluorescence which is distributed regularly over the entire cytoplasm of the granulocytes, leaving the cell nuclei free (cANCA: cytoplasmic pattern), and a predominantly smooth, partly fine granular fluorescence wrapped ribbon-like around the cell nuclei of the granulocytes (pANCA: perinuclear pattern). The cANCA pattern is created by antibodies to proteinase 3. As target antigens of pANCA lactoferrin, myeloperoxidase, elastase, cathepsin G, lysozyme and Beta-glucuronidase has been identified up to now.

cANCA exhibit a high sensitivity and specificity for Wegener's granulomatosis (prevalence 80 to 95%). The antibody titre correlates with the disease activity. Moreover, cANCA can occur in rare cases in microscopic arteritis and polyarteritis nodosa. The main target antigen of cANCA is proteinase 3. Autoantibodies against lactoferrin, myeloperoxidase, elastase and cathepsin G are associated with various autoimmune diseases like systemic lupus erythematodes, rheumatoid arthritis, Felty's syndrome, rapid progressive glomerulonephritis, microscopic polyarteritis, polyarteritis nodosa, Crohn's disease and ulcerative colitis. Autoantibodies against BPI were described in various diseases among them Wegener's granulomatosis, microscopic polyarteritis, colitis ulcerosa, Crohn's disease, vasculitis, autoimmune hepatitis. Antibodies against granulocytes (pANCA) are not only significant in the serological diagnosis of various forms of vasculitis, but also in the differential diagnosis of chronic inflammatory bowel disease. pANCA occurs in 67% of patients with ulcerative colitis and can also occur in Crohn's disease (7%).