V7 (CD101) LIGATION INHIBITS TCR CD3-INDUCED IL-2 PRODUCTION BY BLOCKING CA2+ FLUX AND NUCLEAR FACTOR OF ACTIVATED T-CELL NUCLEAR TRANSLOCATION/

Ligation of the V7 (CD101) molecule on T cells with anti-V7 mAb blocks TCR/CD3-induced proliferation by inhibiting IL-2 transcription. To ex plore the basis for this observation, we analyzed the effects of V7 li gation on CD3/TCR-induced changes in intracellular free Ca2+ and Ca2+- dependent nuclear factor of activated T cells (NF-AT) translocation to the nucleus, which is required for IL-2 transcription. T cells expose d to anti-V7 mAb fluxed Ca2+ transiently, but did not flux Ca2+ in res ponse to subsequent treatment with anti-CD3; however, they recovered t he capacity to flux Ca2+ after treatment with pervanadate, indicating that tyrosine dephosphorylation of a critical V7-related substrate is required in the desensitization process, One such substrate, phospholi pase C (PLC)-gamma(1) becomes tyrosine phosphorylated on CD3/TCR activ ation and mediates inositol triphosphate-dependent Ca2+ flux. Co-cross -linking of T cells with anti-CD3 and anti-V7 resulted in selective in hibition of PLC-gamma(1) tyrosine phosphorylation, which may explain V 7-mediated blockade of anti-CD3-induced Ca2+ flux. Moreover, anti-CD3- induced binding of transcription factors to a consensus NF-AT-binding oligonucleotide, which is dependent on Ca2+, was blocked completely by treatment of the cells with anti-V7, whereas binding to a consensus-a ctivating protein-1 oligonucleotide was unaffected, Western blot analy sis of cytoplasmic and nuclear extracts confirmed that anti-V7 prevent ed nuclear translocation of NF-AT(c) induced by anti-CD3, We conclude that V7 ligation interferes with T cell activation and IL-2 secretion through a Ca2+ and tyrosine kinase-dependent pathway that inhibits PLC -gamma(1) phosphorylation and prevents NF-AT translocation to the nucl eus.