0 8 Distinct distinct JJ 9 18 signaling signaling NN 19 29 properties property NNS 30 38 identify identify VBP 39 51 functionally functionally RB 52 61 different different JJ 62 65 CD4 cd4 NN 66 74 epitopes epitope NNS 74 75 . . . 77 80 The the DT 81 84 CD4 cd4 NN 85 95 coreceptor coreceptor NN 96 105 interacts interact VBZ 106 110 with with IN 111 126 non-polymorphic non-polymorphic JJ 127 134 regions region NNS 135 137 of of IN 138 143 major major JJ 144 162 histocompatibility histocompatibility NN 163 170 complex complex NN 171 176 class class NN 177 179 II ii CD 180 189 molecules molecule NNS 190 192 on on IN 193 211 antigen-presenting antigen-presenting JJ 212 217 cells cell NNS 218 221 and and CC 222 233 contributes contribute VBZ 234 236 to to TO 237 238 T t NN 239 243 cell cell NN 244 254 activation activation NN 254 255 . . . 256 258 We we PRP 259 263 have have VBP 264 276 investigated investigate VBN 277 280 the the DT 281 287 effect effect NN 288 290 of of IN 291 294 CD4 cd4 NN 295 305 triggering triggering NN 306 308 on on IN 309 310 T t NN 311 315 cell cell NN 316 326 activating activating NN 327 334 signals signal NNS 335 337 in in IN 338 339 a a DT 340 348 lymphoma lymphoma NN 349 354 model model NN 355 360 using use VBG 361 371 monoclonal monoclonal JJ 372 382 antibodies antibody NNS 383 384 ( ( ( 384 387 mAb mab NN 387 388 ) ) ) 389 394 which which WDT 395 404 recognize recognize VBP 405 414 different different JJ 415 418 CD4 cd4 NN 419 427 epitopes epitope NNS 427 428 . . . 429 431 We we PRP 432 443 demonstrate demonstrate VBP 444 448 that that IN 449 452 CD4 cd4 NN 453 463 triggering triggering NN 464 472 delivers deliver VBZ 473 480 signals signal NNS 481 488 capable capable JJ 489 491 of of IN 492 502 activating activate VBG 503 506 the the DT 507 512 NF-AT NF-AT NNP 513 526 transcription transcription NN 527 533 factor factor NN 534 539 which which WDT 540 542 is be VBZ 543 551 required require VBN 552 555 for for IN 556 569 interleukin-2 interleukin-2 NN 570 574 gene gene NN 575 585 expression expression NN 585 586 . . . 587 594 Whereas whereas IN 595 604 different different JJ 605 613 anti-CD4 anti-cd4 JJ 614 617 mAb mab NN 618 620 or or CC 621 626 HIV-1 HIV-1 NNP 627 632 gp120 gp120 NN 633 638 could could MD 639 642 all all DT 643 650 trigger trigger VB 651 661 activation activation NN 662 664 of of IN 665 668 the the DT 669 676 protein protein NN 677 685 tyrosine tyrosine NN 686 693 kinases kinase NNS 694 700 p56lck p56lck NN 701 704 and and CC 705 711 p59fyn p59fyn NN 712 715 and and CC 716 731 phosphorylation phosphorylation NN 732 734 of of IN 735 738 the the DT 739 742 Shc Shc NNP 743 750 adaptor adaptor NN 751 758 protein protein NN 758 759 , , , 760 765 which which WDT 766 774 mediates mediate VBZ 775 782 signals signal NNS 783 785 to to TO 786 789 Ras Ras NNP 789 790 , , , 791 795 they they PRP 796 804 differed differ VBD 805 818 significantly significantly RB 819 821 in in IN 822 827 their their PRP$ 828 835 ability ability NN 836 838 to to TO 839 847 activate activate VB 848 853 NF-AT NF-AT NNP 853 854 . . . 855 859 Lack lack NN 860 862 of of IN 863 867 full full JJ 868 878 activation activation NN 879 881 of of IN 882 887 NF-AT NF-AT NNP 888 893 could could MD 894 896 be be VB 897 907 correlated correlate VBN 908 910 to to TO 911 912 a a DT 913 925 dramatically dramatically RB 926 933 reduced reduce VBN 934 942 capacity capacity NN 943 945 to to TO 946 952 induce induce VB 953 960 calcium calcium NN 961 965 flux flux NN 966 969 and and CC 970 975 could could MD 976 978 be be VB 979 991 complemented complement VBN 992 996 with with IN 997 998 a a DT 999 1006 calcium calcium NN 1007 1016 ionophore ionophore NN 1016 1017 . . . 1018 1021 The the DT 1022 1029 results result NNS 1030 1038 identify identify VBP 1039 1051 functionally functionally RB 1052 1060 distinct distinct JJ 1061 1069 epitopes epitope NNS 1070 1072 on on IN 1073 1076 the the DT 1077 1080 CD4 cd4 NN 1081 1091 coreceptor coreceptor NN 1092 1100 involved involve VBN 1101 1103 in in IN 1104 1114 activation activation NN 1115 1117 of of IN 1118 1121 the the DT 1122 1133 Ras/protein Ras/protein NNP 1134 1140 kinase kinase NNP 1141 1142 C C NNP 1143 1146 and and CC 1147 1154 calcium calcium NN 1155 1163 pathways pathway NNS 1163 1164 . . .