MBP and systemic lupus erythematosus: First, we have shown that all ten individual SLE IgG preparations before purification on MBP-Sepharose produced, according to TLC, the same products of specific (corresponding to MBP) X-OP21 and X-OP25 oligopeptides cleavage, but every preparation was characterized by a specific ratio of formation of different cleavage products.