0 9 Induction Induction NNP 10 12 of of IN 13 22 activator activator NN 23 30 protein protein NN 31 32 ( ( ( 32 37 AP)-1 ap)-1 NN 38 41 and and CC 42 49 nuclear nuclear JJ 50 63 factor-kappaB factor-kappab NN 64 66 by by IN 67 71 CD28 cd28 NN 72 83 stimulation stimulation NN 84 92 involves involve VBZ 93 97 both both CC 98 118 phosphatidylinositol phosphatidylinositol NN 119 127 3-kinase 3-kinase NNP 128 131 and and CC 132 138 acidic acidic JJ 139 155 sphingomyelinase sphingomyelinase NN 156 163 signals signal NNS 163 164 . . . 166 167 A a DT 168 173 major major JJ 174 182 obstacle obstacle NN 183 185 in in IN 186 199 understanding understand VBG 200 203 the the DT 204 213 signaling signaling NN 214 220 events event NNS 221 225 that that WDT 226 232 follow follow VBP 233 237 CD28 cd28 NN 238 246 receptor receptor NN 247 255 ligation ligation NN 256 262 arises arise VBZ 263 267 from from IN 268 271 the the DT 272 276 fact fact NN 277 281 that that IN 282 286 CD28 cd28 NN 287 291 acts act VBZ 292 294 as as IN 295 296 a a DT 297 307 costimulus costimulus NN 308 310 to to TO 311 314 TCR TCR NNP 315 325 engagement engagement NN 325 326 , , , 327 333 making make VBG 334 336 it it PRP 337 346 difficult difficult JJ 347 349 to to TO 350 356 assess assess VB 357 360 the the DT 361 369 relative relative JJ 370 382 contribution contribution NN 383 385 of of IN 386 390 CD28 cd28 NN 391 398 signals signal NNS 399 401 as as RB 402 410 distinct distinct JJ 411 415 from from IN 416 421 those those DT 422 424 of of IN 425 428 the the DT 429 432 TCR TCR NNP 432 433 . . . 434 436 To to TO 437 445 overcome overcome VB 446 450 this this DT 451 458 problem problem NN 458 459 , , , 460 462 we we PRP 463 467 have have VBP 468 477 exploited exploit VBN 478 481 the the DT 482 493 observation observation NN 494 498 that that IN 499 508 activated activate VBN 509 514 human human JJ 515 516 T t NN 517 521 cell cell NN 522 528 blasts blast NNS 529 532 can can MD 533 535 be be VB 536 546 stimulated stimulate VBN 547 550 via via IN 551 554 the the DT 555 559 CD28 cd28 NN 560 567 surface surface NN 568 576 molecule molecule NN 577 579 in in IN 580 583 the the DT 584 591 absence absence NN 592 594 of of IN 595 604 antigenic antigenic JJ 605 614 challenge challenge NN 614 615 ; ; : 616 620 thus thus RB 620 621 , , , 622 624 we we PRP 625 629 have have VBP 630 634 been be VBN 635 639 able able JJ 640 642 to to TO 643 650 observe observe VB 651 654 the the DT 655 663 response response NN 664 666 of of IN 667 673 normal normal JJ 674 675 T t NN 676 681 cells cell NNS 682 684 to to TO 685 689 CD28 cd28 NN 690 700 activation activation NN 701 703 in in IN 704 713 isolation isolation NN 713 714 . . . 715 720 Using use VBG 721 725 this this DT 726 732 system system NN 732 733 , , , 734 736 we we PRP 737 745 observed observe VBD 746 750 that that IN 751 755 CD28 cd28 NN 756 767 stimulation stimulation NN 768 770 by by IN 771 785 B7-transfected b7-transfected JJ 786 789 CHO CHO NNP 790 795 cells cell NNS 796 803 induced induce VBD 804 805 a a DT 806 819 proliferative proliferative JJ 820 828 response response NN 829 831 in in IN 832 833 T t NN 834 839 cells cell NNS 840 844 that that WDT 845 848 was be VBD 849 852 not not RB 853 864 accompanied accompany VBN 865 867 by by IN 868 878 measurable measurable JJ 879 883 IL-2 il-2 NN 884 894 production production NN 894 895 . . . 896 903 However however RB 903 904 , , , 905 915 subsequent subsequent JJ 916 924 analysis analysis NN 925 927 of of IN 928 941 transcription transcription NN 942 948 factor factor NN 949 959 generation generation NN 960 968 revealed reveal VBD 969 973 that that IN 974 976 B7 b7 NN 977 988 stimulation stimulation NN 989 996 induced induce VBD 997 1001 both both CC 1002 1011 activator activator NN 1012 1021 protein-1 protein-1 NN 1022 1023 ( ( ( 1023 1027 AP-1 ap-1 NN 1027 1028 ) ) ) 1029 1032 and and CC 1033 1040 nuclear nuclear JJ 1041 1054 factor-kappaB factor-kappab NN 1055 1056 ( ( ( 1056 1065 NF-kappaB NF-kappaB NNP 1065 1066 ) ) ) 1067 1076 complexes complex NNS 1076 1077 , , , 1078 1081 but but CC 1082 1085 not not RB 1086 1091 NF-AT NF-AT NNP 1091 1092 . . . 1093 1095 In in IN 1096 1104 contrast contrast NN 1104 1105 , , , 1106 1116 engagement engagement NN 1117 1119 of of IN 1120 1123 the the DT 1124 1127 TCR TCR NNP 1128 1130 by by IN 1131 1136 class class NN 1137 1139 II ii CD 1140 1156 MHC/superantigen mhc/superantigen NN 1156 1157 , , , 1158 1164 either either CC 1165 1169 with with IN 1170 1172 or or CC 1173 1180 without without IN 1181 1185 CD28 cd28 NN 1186 1194 ligation ligation NN 1194 1195 , , , 1196 1204 resulted result VBD 1205 1207 in in IN 1208 1211 the the DT 1212 1221 induction induction NN 1222 1224 of of IN 1225 1230 NF-AT NF-AT NNP 1230 1231 , , , 1232 1236 AP-1 ap-1 NN 1236 1237 , , , 1238 1241 and and CC 1242 1251 NF-kappaB NF-kappaB NNP 1252 1254 as as RB 1255 1259 well well RB 1260 1262 as as IN 1263 1267 IL-2 il-2 NN 1268 1278 production production NN 1278 1279 . . . 1280 1285 Using use VBG 1286 1295 selective selective JJ 1296 1306 inhibitors inhibitor NNS 1306 1307 , , , 1308 1310 we we PRP 1311 1323 investigated investigate VBD 1324 1327 the the DT 1328 1337 signaling signaling NN 1338 1346 pathways pathway NNS 1347 1355 involved involve VBN 1356 1358 in in IN 1359 1362 the the DT 1363 1376 CD28-mediated cd28-mediated JJ 1377 1386 induction induction NN 1387 1389 of of IN 1390 1394 AP-1 AP-1 NNP 1395 1398 and and CC 1399 1408 NF-kappaB NF-kappaB NNP 1408 1409 . . . 1410 1414 This this DT 1415 1423 revealed reveal VBD 1424 1428 that that IN 1429 1438 NF-kappaB NF-kappaB NNP 1439 1449 generation generation NN 1450 1453 was be VBD 1454 1463 sensitive sensitive JJ 1464 1466 to to TO 1467 1478 chloroquine chloroquine NN 1478 1479 , , , 1480 1482 an an DT 1483 1492 inhibitor inhibitor NN 1493 1495 of of IN 1496 1502 acidic acidic JJ 1503 1519 sphingomyelinase sphingomyelinase NN 1519 1520 , , , 1521 1524 but but CC 1525 1528 not not RB 1529 1531 to to TO 1532 1535 the the DT 1536 1556 phosphatidylinositol phosphatidylinositol NN 1557 1565 3-kinase 3-kinase NNP 1566 1575 inhibitor inhibitor NN 1575 1576 , , , 1577 1587 wortmannin wortmannin NN 1587 1588 . . . 1589 1591 In in IN 1592 1600 contrast contrast NN 1600 1601 , , , 1602 1606 AP-1 ap-1 NN 1607 1617 generation generation NN 1618 1621 was be VBD 1622 1631 inhibited inhibit VBN 1632 1634 by by IN 1635 1645 wortmannin wortmannin NN 1646 1649 and and CC 1650 1653 was be VBD 1654 1658 also also RB 1659 1667 variably variably RB 1668 1677 sensitive sensitive JJ 1678 1680 to to TO 1681 1692 chloroquine chloroquine NN 1692 1693 . . . 1694 1699 These these DT 1700 1704 data datum NNS 1705 1712 suggest suggest VBP 1713 1717 that that IN 1718 1720 in in IN 1721 1730 activated activate VBN 1731 1737 normal normal JJ 1738 1739 T t NN 1740 1745 cells cell NNS 1745 1746 , , , 1747 1759 CD28-derived cd28-derived JJ 1760 1767 signals signal NNS 1768 1771 can can MD 1772 1781 stimulate stimulate VB 1782 1795 proliferation proliferation NN 1796 1798 at at IN 1799 1804 least least JJS 1805 1807 in in IN 1808 1812 part part NN 1813 1816 via via IN 1817 1826 NF-kappaB NF-kappaB NNP 1827 1830 and and CC 1831 1835 AP-1 ap-1 NN 1836 1846 generation generation NN 1846 1847 , , , 1848 1851 and and CC 1852 1856 that that IN 1857 1861 this this DT 1862 1870 response response NN 1871 1875 uses use VBZ 1876 1880 both both CC 1881 1887 acidic acidic JJ 1888 1904 sphingomyelinase sphingomyelinase NN 1905 1908 and and CC 1909 1929 phosphatidylinositol phosphatidylinositol NN 1930 1945 3-kinase-linked 3-kinase-linked JJ 1946 1954 pathways pathway NNS 1954 1955 . . .