Immunoglobulin deposits in bladder epithelium and vessels in interstitial cystitis: possible relationship to circulating anti-intermediate filament autoantibodies.

Sera from patients suffering from interstitial cystitis (IC) reacted with bright staining of the bladder epithelium and vascular endothelium when tested for autoantibodies by indirect immunofluorescence using normal bladder tissue as target antigen. When tested for autoantibodies using cultured cells as antigen the antibodies were found to be directed against cytoskeletal intermediate filaments (IMF). Sera from 43 IC patients had a high incidence and high titers of anti-IMF autoantibodies as compared to both healthy individuals and patients suffering from other urological or surgical diseases. The results suggest that anti-IMF autoantibodies may be involved in the perpetuating chronic type of tissue injury seen in these patients. The antibodies were of the IgM class. In vivo deposits of IgM in patient bladder biopsies localized similarly to the autoantibodies; epithelial tissue showed deposits in 19% and vascular tissue, deposits in more than 50% of the patients, often together with complement components Clq,C3, or C4. In addition, subendothelial deposits associated with fibrillar structures could be observed. The results suggest a possible relationship between the in vivo IgM deposits in the bladder epithelium and vascular endothelium, on one hand, and the presence of anti-IMF antibodies capable of reacting with these cell structures, on the other hand. However, as the autoantibodies have to gain access to intracellular structures in order to cause in vivo deposits, primary tissue injury has to be postulated.