Gene fragments of each of the target proteins were amplified by PCR separately. cases, unique epitopes were observed for one of the immunizations. The results suggest that polyclonal antibodies generated by repeated immunizations do not display an identical epitope pattern, although many of the epitopes are comparable. == Introduction == As antibodies have proven to be an exceptional tool to study the proteins of human biology and disease the need to produce well-validated reagents of this kind is obvious[1]. Several initiatives have started to generate antibodies and other affinity reagents in a systematic genome-wide manner, including the Human Protein Atlas project[2], the SH2-consortium[3]and the protein binder consortiums[4]. In addition, various commercial providers have generated several hundred thousands antibodies towards human proteins, and approximately 150,000 of these antibodies are outlined in the community-based Antibodypedia portal[5]. The Human Protein Atlas[6]with information on more than 11,000 protein-coding genes, contains tissue Olutasidenib (FT-2102) profiles for more than 60 human cell types covering 48 tissues and organs, including liver, kidney, heart, different parts of the brain, Olutasidenib (FT-2102) the gastrointestinal tract etc. which are based on more than 14,000 commercially available antibodies. An important issue in this regard is the renewability of antibodies. Ideally, when results are obtained with well-validated antibodies, the reagent should be available to the scientific community indefinitely for further in-depth functional studies. This is the driving pressure for efforts trying to generate truly renewable affinity reagents, such as monoclonal antibodies using hybridoma cells or recombinant protein binders, such as antibody-fragments[7], scaffold binders[8]or nucleic acid based binders, such as aptamers and somamers[9]. However, more than 70% of the antibodies in Antibodypedia and Rabbit polyclonal to AGER 80% of the antibodies Olutasidenib (FT-2102) in the Human Protein Atlas are polyclonal antibodies[10]. Here, the limited availability of many polyclonal antibodies is a great concern, since there only exist a limited supply from the original immunization. The degree of renewability of polyclonal antibodies has been questioned, due to possible batch-to-batch variations when a follow-up immunization is done to generate new quantities of antibodies. In the diagnostic industry, this problem has been over-come by immunizing large animals, such as sheep or goat, to generate large quantities of antibodies. Alternatively, many animals, such as rabbits, are immunized with the same antigen and the sera from many animals are pooled to generate a large supply of antibodies with the same batch number. However, despite the frequent use of polyclonal antibodies, few studies have been performed in the past to estimate the degree of reproducibility when a new batch of polyclonal antibodies have been generated by immunization of a second animal. Recently, Larsson et al[11]used two recombinant antigens in repeated immunizations and decided the epitopes and immunohistochemistry staining patterns for the obtained antibodies. They concluded that all immunizations detected the correct band in Western blotting, but they rendered different staining patterns in IHC possibly related to their different epitope patterns. In the work by Geysen et al[12], the comparison of seven sera from outbred rabbits immunized with myohemerythrin, showed that no antibody specificity was common in all seven rabbits. Established methods for epitope mapping of antibodies entails chemical synthesis of peptides[13],[14]or peptide display on phages[15],[16]. Recently, we have explained two independent methods for epitope mapping of antibodies[17], as schematically layed out inFigure 1. The first method relies on bacterial surface display Olutasidenib (FT-2102) onStaphylococcus carnosusin which the gene encoding the target protein is usually fragmented, Olutasidenib (FT-2102) cloned into an expression vector and subsequently launched intoS. carnosushost cells (Physique 1A). A library of bacterial cells is created, each member with a small fragment of the original gene expressed on the surface of the cell. The cells are incubated with the antibody to be mapped labeled with a fluorescent dye and the cells are analyzed in a circulation cytometer so that cells expressing fragments bound by the antibody can be collected. These cells are produced, the insert of the expression vector DNA sequenced and.