Identification of conformational epitopes on fragment crystallizable region of human Immunoglobulin G by immunoinformatic

Background: Immunoglobulins are a group of proteins have important role in defense against microorganisms. Human immunoglobulins are divided into five classes: IgA, IgM, IgD, IgE and IgG. Immunoglobulin G (IgG) is the highest abundant antibody in serum and extravascular fluids. The extent of serum IgG is related to severity of several diseases such as infections, so IgG has great diagnostic worth. Accurate measurement of IgG, needs exact and sensitive diagnostic instruments such as human IgG- specific monoclonal antibodies. Moreover, targeting of IgG has been useful in treatment of a number of diseases. According to experimental studies the Fc region of human IgG is highly immunogenic. Immunoinformatic is a division of immunology uses the computational biology for more precise diagnosis of diseases. The aim of this study was determination of conformational epitopes in the fragment of crystallizable (Fc) fragment of human IgG by immunoinformatic. Methods: The amino acid residues and third structure of reference human IgG were found in protein data bank (PDB). Second IgG structure was defined by Phyre2 software (http://www.sbg.bio.ic.ac.uk/~phyre2/). Conformational epitopes of the Fc fragment in human IgG were specified by ElliPro (http://tools.iedb.org/ellipro/) and DiscoTope (http://www.cbs.dtu.dk/services/DiscoTope) softwares. Results: In this study two conformational epitopes (one in constant heavy chain 2 (CH2) domain and another one common between CH2 and CH3 domains) sited in Fc fragment of human IgG were determined by ElliPro software. Also, two conformational epitopes (Both common between CH2 and CH3 domains) located to Fc fragment of human IgG were determined by DiscoTope software. Conclusion: In this study a number of conformational epitopes located to Fc fragment of human IgG were determined by two immunoinformatic softwares (ElliPro and DiscoTope). The epitopes recognized by both softwares were situated in CH2, CH3 or both of these domains in the human IgG heavy chain. Thus, it seems that CH2 and CH3 domains of Fc region in human IgG are highly immunogenic. Moreover, ElliPro and DiscoTope softwares can be useful tools for identification of epitopes located to Fc fragment of human IgG.