T-T hybridomas recognising multiple cross-reactive T-epitopes with SmD and cross-reactive T-epitopes shared by SmD, SmB, A-RNP and Ro60. (A) Hybridoma D1438–7-21 was cloned twice and recognises two different regions within SmD. Further mapping with SmD 15mer peptides overlapping by 12 aa showed H1438–7-21 reacts with SmD6–20 and SmD57–71. These two SmD peptides share cross-reactive T-epitopes although they do not have significant sequence homology. (B) Summary of hybridomas reactive with two or more SmD T epitopes shows that SmD have multiple intramolecular cross-reactive T-epitopes. T-cell epitope in bold means they are the dominant epitope within the cross-reactive epitopes with other epitope(s) inducing <70% of interleukin (IL)-2. (C) Hybridoma F140–9 reacts with SmD66–80. It reacts to SmD, SmB and A-RNP in a dose-dependent manner (left panel). Their responses are DR3 restricted. It reacts much better to SmB. It reacts to Ro60132–277 and Ro6 0 263–406 in a HLA-DR3 restricted manner as shown in the right panel. Thus F140–9 reacts with a T-epitope shared among SmD, SmB, A-RNP and Ro60. (D) Summary of T-T hybridomas reactive with SmD and SmB (four clones), SmD, SmB and A-RNP (three clones) and SmD, SmB, A-RNP and Ro60 (one clone).