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From the * Ben May Institute for Cancer Research, Committee on Immunology, Department of
Pathology; § Department of Medicine, University of Chicago, Illinois 60637; and Anti-CD3 monoclonal antibodies (mAbs) are potent immunosuppressive agents used in clinical
transplantation. However, the activation-related adverse side effects associated with these mAbs
have prompted the development of less toxic nonmitogenic anti-CD3 mAb therapies. At present,
the functional and biochemical consequences of T cell exposure to nonmitogenic anti-CD3 is
unclear. In this study, we have examined the early signaling events triggered by a nonmitogenic anti-CD3 mAb. Like the mitogenic anti-CD3 mAb, nonmitogenic anti-CD3 triggered changes
in the T cell receptor (TCR) complex, including
Protein Design
Laboratories, Mountain View, California 94043
chain tyrosine phosphorylation and ZAP-70
association. However, unlike the mitogenic anti-CD3 stimulation, nonmitogenic anti-CD3 was
ineffective at inducing the highly phosphorylated form of
(p23) and tyrosine phosphorylation
of the associated ZAP-70 tyrosine kinase. This proximal signaling deficiency correlated with
minimal phospholipase C
-1 phosphorylation and failure to mobilize detectable Ca2+. Not
only did biochemical signals delivered by nonmitogenic anti-CD3 resemble altered peptide
ligand signaling, but exposure of Th1 clones to nonmitogenic anti-CD3 also resulted in functional anergy. Finally, a bispecific anti-CD3 × anti-CD4 F(ab)
2 reconstituted early signal
transduction events and induced proliferation, suggesting that defective association of lck with
the TCR complex may underlie the observed signaling differences between the mitogenic and
nonmitogenic anti-CD3.
This article has been cited by other articles:
Phosphorylation. Science
281: 572-575
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