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It was with interest that we read the paper by Terjung et al1, in a recent issue of Gut, where human myeloid cell-specific β-tubulin isotype 5 was identified as the target antigen of atypical p-ANCA in autoimmune liver disorders. The authors suggest cross-reactivity with the bacterial protein FtsZ, probably reflecting an abnormal immune response to intestinal microorganisms.1
In attempts to identify novel anti-nuclear and anti-neutrophil antibodies in autoimmune hepatitis, we performed 2D gel electrophoresis and western blotting starting from nuclear HeLa cell extracts or enriched nuclear envelope extracts from HL60 cells or neutrophils. The blots were incubated with serum samples from patients with autoimmune hepatitis and controls. Spots to which there was reactivity with serum from patients but not from controls were excised and identified by MALDI-TOF/TOF.
In experiments in which we used non-myeloid HeLa cell extracts, a prominent protein spot of 49 670.82 Da (pI 4.78) was identified as β-tubulin isotype 5 (TBB5). The immune reactivity to tubulin was confirmed by western blotting. A cohort (n=468) of patients with autoimmune liver disease, viral hepatitis, inflammatory bowel disease and vasculitis was evaluated for reactivity to tubulin by ELISA using porcine tubulin (figure 1A) and recombinant human TBB5 (figure 1B …