4588
There are two immunogenic sites on the type A influenza A / Japan / 57 ( H2N2 ) hemagglutinin ( HA ) that can be recognized by class I major histocompatibility complex ( MHC ) , H - 2Kd - restricted cytolytic T lymphocytes ( CTLs ) .
 hemagglutinin, HA, class I major histocompatibility complex, MHC, H - 2Kd
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 hemagglutinin, HA, class I major histocompatibility complex, MHC, H - 2Kd