The present invention provides a prophylactic or therapeutic composition for graft-versus-
host disease (GVHD). There is provided a prophylactic or therapeutic composition for GVHD, which comprises
bacteria belonging to any
genus selected from the group consisting of the following genera: Blautia,
Clostridium, unclassified
Clostridiales,
Actinomyces, Parabacteroides, Lachnoclostridium,
Bacteroides, Faecalibacterium, unclassified Lachnospiraceae,
Roseburia, Ruminococcus, unclassified
Firmicutes, Dorea, Phascolarctobacterium, Sutterella, Megamonas, Collinsella,
Eubacterium, and Coprococcus, etc., or any combination of
bacteria belonging to these genera.