0 12 Differential differential JJ 13 23 regulation regulation NN 24 26 of of IN 27 42 proto-oncogenes proto-oncogene NNS 43 48 c-jun c-jun NN 49 52 and and CC 53 58 c-fos c-fos NN 59 61 in in IN 62 63 T t NN 64 75 lymphocytes lymphocyte NNS 76 85 activated activate VBN 86 93 through through IN 94 98 CD28 cd28 NN 98 99 . . . 101 104 The the DT 105 106 T t NN 107 111 cell cell NN 112 119 surface surface NN 120 128 molecule molecule NN 129 133 CD28 cd28 NN 134 139 binds bind VBZ 140 142 to to TO 143 150 ligands ligand NNS 151 153 on on IN 154 163 accessory accessory NN 164 169 cells cell NNS 170 173 and and CC 174 178 APCs apc NNS 178 179 , , , 180 187 playing play VBG 188 190 an an DT 191 200 important important JJ 201 214 costimulatory costimulatory JJ 215 219 role role NN 220 222 in in IN 223 226 the the DT 227 235 response response NN 236 238 of of IN 239 240 T t NN 241 246 cells cell NNS 247 249 to to TO 250 253 Ags ag NNS 253 254 . . . 255 258 Our our PRP$ 259 268 knowledge knowledge NN 269 271 of of IN 272 275 the the DT 276 289 intracellular intracellular JJ 290 299 signaling signaling NN 300 308 pathways pathway NNS 309 316 coupled couple VBN 317 319 to to TO 320 324 this this DT 325 333 receptor receptor NN 334 336 is be VBZ 337 347 incomplete incomplete JJ 347 348 . . . 349 351 In in IN 352 360 addition addition NN 361 363 to to TO 364 374 activation activation NN 375 377 of of IN 378 391 phospholipase phospholipase NN 392 393 C C NNP 394 399 gamma gamma NN 400 401 1 1 CD 401 402 , , , 403 411 ligation ligation NN 412 414 of of IN 415 419 this this DT 420 428 receptor receptor NN 429 433 also also RB 434 439 seems seem VBZ 440 442 to to TO 443 451 activate activate VB 452 453 a a DT 454 473 calcium-independent calcium-independent JJ 473 474 , , , 475 488 CD28-specific cd28-specific JJ 489 496 pathway pathway NN 496 497 . . . 498 500 In in IN 501 505 this this DT 506 511 paper paper NN 511 512 , , , 513 515 we we PRP 516 522 report report VBP 523 527 that that IN 528 541 cross-linking cross-linking NN 542 544 of of IN 545 549 CD28 cd28 NN 550 551 ( ( ( 551 554 but but CC 555 558 not not RB 559 562 CD2 cd2 NN 562 563 , , , 564 567 CD5 CD5 NNP 567 568 , , , 569 574 LFA-1 lfa-1 NN 574 575 , , , 576 578 or or CC 579 582 CD7 cd7 NN 582 583 ) ) ) 584 589 leads lead VBZ 590 592 to to TO 593 595 an an DT 596 605 elevation elevation NN 606 608 of of IN 609 614 c-jun c-jun NN 615 619 mRNA mRNA NNP 619 620 , , , 621 625 with with IN 626 630 only only RB 631 638 minimal minimal JJ 639 649 activation activation NN 650 652 of of IN 653 658 c-fos c-fos NN 659 669 expression expression NN 669 670 . . . 671 685 CD28-dependent cd28-dependent JJ 686 695 induction induction NN 696 698 of of IN 699 704 c-jun c-jun NN 705 715 expression expression NN 716 724 requires require VBZ 725 732 protein protein NN 733 741 tyrosine tyrosine NN 742 748 kinase kinase NNP 749 757 activity activity NN 757 758 , , , 759 762 but but CC 763 767 does do VBZ 768 771 not not RB 772 778 depend depend VB 779 781 on on IN 782 792 activation activation NN 793 795 of of IN 796 797 a a DT 798 805 phorbol phorbol NN 806 822 ester-responsive ester-responsive JJ 823 830 protein protein NN 831 837 kinase kinase NNP 838 839 C C NNP 840 842 or or CC 843 852 elevation elevation NN 853 855 of of IN 856 865 cytosolic cytosolic JJ 866 873 calcium calcium NN 873 874 . . . 875 886 Furthermore furthermore RB 886 887 , , , 888 902 CD28-dependent cd28-dependent JJ 903 912 elevation elevation NN 913 915 of of IN 916 921 c-jun c-jun NN 922 926 mRNA mRNA NNP 927 931 does do VBZ 932 935 not not RB 936 942 appear appear VB 943 945 to to TO 946 948 be be VB 949 957 mediated mediate VBN 958 960 at at IN 961 964 the the DT 965 970 level level NN 971 973 of of IN 974 978 mRNA mrna NN 979 988 stability stability NN 988 989 . . . 990 991 A a DT 992 1001 mechanism mechanism NN 1002 1004 is be VBZ 1005 1014 suggested suggest VBN 1015 1022 whereby whereby WRB 1023 1033 expression expression NN 1034 1036 of of IN 1037 1042 c-jun c-jun NN 1043 1046 and and CC 1047 1051 junB junb NN 1051 1052 , , , 1053 1055 in in IN 1056 1059 the the DT 1060 1067 absence absence NN 1068 1070 of of IN 1071 1078 members member NNS 1079 1081 of of IN 1082 1085 the the DT 1086 1089 fos fos NN 1090 1096 family family NN 1096 1097 , , , 1098 1101 can can MD 1102 1109 prevent prevent VB 1110 1123 inappropriate inappropriate JJ 1124 1134 activation activation NN 1135 1137 of of IN 1138 1139 T t NN 1140 1145 cells cell NNS 1146 1152 caused cause VBN 1153 1155 by by IN 1156 1164 ligation ligation NN 1165 1167 of of IN 1168 1172 CD28 cd28 NN 1173 1175 in in IN 1176 1179 the the DT 1180 1187 absence absence NN 1188 1190 of of IN 1191 1192 a a DT 1193 1201 specific specific JJ 1202 1211 antigenic antigenic JJ 1212 1220 stimulus stimulus NN 1220 1221 . . .