0 12 Constitutive constitutive JJ 13 23 expression expression NN 24 26 of of IN 27 35 specific specific JJ 36 46 interferon interferon NN 47 55 isotypes isotype NNS 56 58 in in IN 59 69 peripheral peripheral JJ 70 75 blood blood NN 76 86 leukocytes leukocyte NNS 87 91 from from IN 92 98 normal normal JJ 99 110 individuals individual NNS 111 114 and and CC 115 117 in in IN 118 130 promonocytic promonocytic JJ 131 135 U937 u937 NN 136 141 cells cell NNS 141 142 . . . 144 156 Constitutive constitutive JJ 157 167 expression expression NN 168 170 of of IN 171 181 IFN-alpha5 IFN-alpha5 NNP 182 185 and and CC 186 194 IFN-beta IFN-beta NNP 195 198 was be VBD 199 207 detected detect VBN 208 210 in in IN 211 220 different different JJ 221 229 lymphoid lymphoid JJ 230 235 cells cell NNS 236 245 including include VBG 246 256 peripheral peripheral JJ 257 262 blood blood NN 263 274 mononuclear mononuclear JJ 275 280 cells cell NNS 281 285 from from IN 286 292 normal normal JJ 293 304 individuals individual NNS 305 314 following follow VBG 315 328 amplification amplification NN 329 331 of of IN 332 335 IFN IFN NNP 336 340 mRNA mRNA NNP 341 343 by by IN 344 351 reverse reverse JJ 352 376 transcriptase-polymerase transcriptase-polymerase NN 377 382 chain chain NN 383 391 reaction reaction NN 392 395 and and CC 396 402 direct direct JJ 403 413 sequencing sequencing NN 414 416 of of IN 417 420 the the DT 421 430 amplified amplify VBN 431 438 product product NN 438 439 . . . 440 443 The the DT 444 453 activated activated JJ 454 458 form form NN 459 461 of of IN 462 465 the the DT 466 484 interferon-induced interferon-induced JJ 485 498 transcription transcription NN 499 505 factor factor NN 506 513 complex complex NN 514 519 ISGF3 isgf3 NN 520 523 was be VBD 524 528 also also RB 529 537 detected detect VBN 538 540 in in IN 541 548 nuclear nuclear JJ 549 557 extracts extract NNS 558 562 from from IN 563 572 uninduced uninduced JJ 573 578 cells cell NNS 578 579 . . . 580 587 Culture Culture NNP 588 600 supernatants supernatant NNS 601 605 from from IN 606 615 uninduced uninduced JJ 616 620 U937 u937 NN 621 626 cells cell NNS 627 631 were be VBD 632 636 also also RB 637 642 found find VBN 643 645 to to TO 646 654 activate activate VB 655 657 an an DT 658 662 ISRE isre NN 663 669 cloned clone VBN 670 678 upstream upstream RB 679 681 of of IN 682 685 the the DT 686 696 luciferase luciferase NN 697 705 reporter reporter NN 706 710 gene gene NN 710 711 , , , 712 722 indicating indicate VBG 723 726 the the DT 727 735 presence presence NN 736 738 of of IN 739 749 endogenous endogenous JJ 750 753 IFN IFN NNP 754 762 activity activity NN 763 773 equivalent equivalent JJ 774 776 to to TO 777 790 approximately approximately RB 791 794 0.3 0.3 CD 795 797 to to TO 798 801 0.5 0.5 CD 802 807 IU/mL iu/ml NN 807 808 . . . 809 813 This this DT 814 824 endogenous endogenous JJ 825 828 IFN ifn NN 829 832 was be VBD 833 837 also also RB 838 843 shown show VBN 844 846 to to TO 847 851 play play VB 852 853 a a DT 854 858 role role NN 859 861 in in IN 862 873 maintaining maintain VBG 874 877 the the DT 878 883 basal basal JJ 884 889 level level NN 890 892 of of IN 893 903 expression expression NN 904 906 of of IN 907 910 the the DT 911 916 major major JJ 917 935 histocompatibility histocompatibility NN 936 941 class class NN 942 943 I i CD 944 949 genes gene NNS 950 952 in in IN 953 961 lymphoid lymphoid JJ 962 967 cells cell NNS 967 968 . . . 969 974 These these DT 975 982 results result NNS 983 990 suggest suggest VBP 991 995 that that IN 996 1006 IFN-alpha5 IFN-alpha5 NNP 1007 1010 and and CC 1011 1019 IFN-beta IFN-beta NNP 1020 1023 are be VBP 1024 1032 produced produce VBN 1033 1035 at at IN 1036 1039 low low JJ 1040 1046 levels level NNS 1047 1049 in in IN 1050 1056 normal normal JJ 1057 1064 tissues tissue NNS 1065 1068 and and CC 1069 1073 play play VB 1074 1076 an an DT 1077 1086 important important JJ 1087 1091 role role NN 1092 1094 in in IN 1095 1098 the the DT 1099 1109 regulation regulation NN 1110 1112 of of IN 1113 1117 cell cell NN 1118 1126 function function NN 1127 1130 and and CC 1131 1133 in in IN 1134 1137 the the DT 1138 1149 maintenance maintenance NN 1150 1152 of of IN 1153 1164 homeostasis homeostasis NN 1164 1165 . . .