Embryonic and placental expression of Mhc class Ib genes. RT-PCR analysis was performed on total RNA isolated from E9.5–14.5 of C57BL/6J embryos and placentas. As for the E14.5 embryo, RT-PCR was conducted using cDNA as templates, derived from total RNA isolated from the brain and liver. Identities of bands were confirmed by amplified sizes and by sequencing (indicated by yellow asterisk). The same reaction conditions were used for PCR.