A peptide of human muscarinic acetylcholine receptor 3 is antigenic in primary Sjögren's syndrome

The pSS sera resulted in significantly higher mean optical densities than those of the healthy controls (KRSE: 0.4149 vs 0.1494, p < 0.0001; GST-KRSE 0.4765 vs 0.1764, p < 0.0001). The immunological recognition with the recombinant fusion antigen was significantly better than that for the free peptide (p = 0.0068). The sensitivities of the assays were 77.5% (KRSE) and 97% (GST-KRSE). The results of the concentration-dependent inhibition assays by the two systems of peptide presentation indicated that the KRSE sequence is specific for pSS sera. This is the first demonstration of the antigenicity of a novel peptide fragment of the human m3AChR in pSS. The analysed peptide could be of diagnostic relevance.