The X box region is critical for directing the expression of class II major histocompatibility complex genes in B lymphocytes .
the x box region is critical for directing the expression of class ii major histocompatibility complex genes in b lymphocytes .
O B-DNA_domain_or_region I-DNA_domain_or_region I-DNA_domain_or_region O O O O O O O B-DNA_family_or_group I-DNA_family_or_group I-DNA_family_or_group I-DNA_family_or_group I-DNA_family_or_group I-DNA_family_or_group O B-cell_type I-cell_type O