Immunogen sequence: PRHSTLSSPK TMVNISDQTM HSIPTSPSHG SIAAYQGYSP QRTYRSEVSS PIQRGDVTID RRHRAHHPKH VYVPDRRSVP AGLTLQSVSP QSLQGKTLSQ D Highest antigen sequence identity to the following orthologs: Mouse - 87%, Rat - 81%. Histones are basic nuclear proteins