Abstract: Peptides are proposed with antigenic or immunogenic determinants, which result from autoantibodies in the body fluids of patients, who are suffering from systemic lupus erythematosus (SLE). In the case of the peptides it is preferably a question of the C terminus of H1 with the sequence section 187-211 and the N termini of H2B with the sequence sections 1-35 and 36-76, which are capable of cross reactions with the autoantibodies (anti-histone-antibodies). The invention furthermore provides ways of forming monoclonal antibodies and antiidiotypical antibodies, which are directed against autoantibodies. The diagnosis of SLE is possible in accordance with the invention with a high degree of certainty and the monoclonal antibodies directed against the autoantibodies are suitable for the production of medicaments for the therapy of SLE.