β5t is incorporated into 20S proteasomes with β1i and β2i in the human thymus. (A) Extracts of human neonatal thymi were immunoprecipitated with anti-α6 or anti-β5t Ab, followed by immunoblotting with the indicated Abs. IP indicates immunoprecipitation. (B) Immunofluorescence staining of the neonatal thymus using anti-β1i or anti-β2i Ab. Each panel shows an image of the cortical area. β1i and β2i (in red) are expressed in keratin-expressing cTECs (in green). Bar represents 50 μM.