Immunogen sequence: EINGSADHRM FSFHNGGVQI SCKYPETVQQ LKMRLFRERE VLCELTKTKG SGNAVSIKNP MLCLYHLSNN SVSFFLNNPD SSQGSYYFCS LSIFDPPPFQ ERNLSGGYLH IYESQLCCQL KL. ICOS (CD278) encodes a protein that is a member of the CD28 and CTLA-4 cell-surface receptor famil