Abstract
Random peptide libraries (RFL) displayed on phage are being increasingly used to identify mimics of epitopes (mimotopes) in antigens (1). These RPL's typically provide over 109 peptide at a fraction of the cost of chemically synthesized RPL's. The RFL are constructed by inserting 21 to 36 random nudeotides into the gene for an appropriate coat protein in a phage which is propagated in Ecoll. Particularly dear mimotopes have been obtained with monoclonal antibodies and with a few polyclonal antibodies against viruses. Now that good quality RPL are available commercially they will be used in attempts to identify novel autoantigens which react with antibodies present in patients with autoimmune diseases. Once the peptide mimic of the autoantigen is obtained, it can be used to affinity to purify the autoantibody, which can then be used to locate the real autoantigen in a cDNA library from the target organ. It is particularly difficult with human sera to obtain mimotopes which are specific for a disease. Strategies are necessary to increase the chance of selecting a specific peptide where the level of autoantibody in serum could be low and it is likely to be only one of thousands of antibodies with no relevance to the disease. Despite these difficulties interesting results are emerging in rheumatoid arthritis (2), immune thrombocy topenic purpura (3) and multiole sclerosis (4).